Title of Invention	"A CATIONIC PORPHYRIN COMPOUNDS OF FORMULA I"
Abstract	The present invention relates to a cationic porphyrin compounds of formula I wherein N, M, X1, X2, X3, X4, Y1, Y2 and Y3 are described in the specification.

Full Text

The present invention relates to a cationic porphyrin compounds of formula I. Field The present invention relates to compounds and uses thereof in the treatment of a medical condition for which a photodynamic compound is indicated and, in particular, in the curative or prophylactic treatment of microbial colonisation and infection. Background The resistance to antibiotics developed by an increasing number of microorganisms is recognised to be a worldwide health problem (Tunger et at., 2000, Int. J. Microb. Agents 15:131-135; Jorgensen et ah, 2000, Clin. Infect. Dis. 30:799-808). Thus, the development of non-antibiotic approaches for killing microorganisms is urgently required for controlling antibiotic-untreatable infections and limiting the development of additional antibiotic-resistant strains. The treatment of microbial infections by photodynamic therapy (PDT) represents a valuable alternative method for eradicating bacteria since it involves a mechanism which is markedly different from that typical of most antibiotics. Thus, PDT is based on the use of a photo sensitising molecule that, once activated by light, generates oxygen reactive species that are toxic for a large variety of prokaryotic and eukaryotic cells including bacteria, mycoplasmas and yeasts (Malik et al., 1990, J. Photochem. Photobiol. B Biol 5:281-293; Bertoloni et al, 1992, Microbios 71:33-46). Importantly, the photosensitising activity of many photodynarnic agents against bacteria is not impaired by the resistance to antibiotics but, instead, depends mainly on their chemical structure (Malik et al, 1992, J. Photochem. Photobiol. B Biol. 14:262-266). Various types of neutral and anionic photosensitising agents exhibit a pronounced phototoxic activity against Gram positive bacteria. However, such photosensitising agents exert no appreciable cytotoxic activity against Gram negative bacteria unless the permeability of the outer membrane is altered by treatment with ethylene diamine tetra-acetic acid (EDTA) or polycations (Bertoloni etal, l99Q,FEMSMicrobiol. Lett. 71: 149-156; Nitzan et al, 1992, Photochem. Photobiol. 55:89-97). It is believed that the cellular envelope of Gram negative bacteria, which is more complex and thicker than that of Gram positive bacteria, prevents an efficient binding of the photosensitising agent or intercepts and deactivates the cytotoxic reactive species photogenerated by the photosensitising agent (Ehrenberg et al, 1985, Photochem. Photobiol. 41:429-435; Valduga et al, 1993, J. Photochem. Photobiol B. Biol 21:81-86). In contrast, positively charged (cationic) photosensitising agents, including porphyrins and phmalocyanines, promote efficient inactivation of Gram negative bacteria without the need for modifying the natural structure of the cellular envelope (Merchat et al, 1996, J. Photochem. Photobiol B. Biol 32:153-157; Minnock et al, 1996, J. Photochem. Photobiol B. Biol 32:159-164). It appears that the positive charge favours the binding of the photosensitising agent at critical cellular sites that, once damaged by exposure to light, cause the loss of cell viability (Merchat et al, 1996, J. Photochem. Photobiol. B. Biol. 35:149-157). Thus, it has been reported that Escherichia coif is efficiently inactivated by visible light after incubation with the cationic 5,10,15,20-tetrakis-(4-^-methylpyridyl)-porphine (T4MPyP) (Valduga et al.3 1999, Biochem. Biophys. Res. Commun. 256:84-88). The phototoxic activity of this porphyrin is mainly mediated by the impairment of the enzymic and transport functions of both the outer and cytoplasmic membranes, rather than by binding to DNA. However, the utility of known poiphyrin-based photodynaniic therapy agents is limited due to their toxicity against mammalian host tissue cells, i.e. the compounds are unable to differentiate between target microbial cells and host cells. In addition, the utility of known porphyrin-based photodynaniic therapy agents is further limited by their relatively low potency for target microbial cells. Hence, there is a need for porphyrin-based compounds with improved toxicity profiles and high potency, which can be used in PDT to preferentially kill microbial cells. Summary According to a first aspect of the invention, there is provided a compound of formula I wherein: Xi, X2, Xs and X4 independently represent (i.e. are the same or different) a hydrogen atom, a lipophilic moiety, a phenyl group, a lower alkyl, alkaryl or aralkyl group, or a cationic group of the following formula; -L-R1-N+(R2)(R3)R4 wherein: L is a linldng moiety or is absent; ri represents lower alkylene, lower allcenylene or lower alkynylene, which is optionally substituted by one or more substituents selected from lower alkyl, lower alkylene (optionally interrupted with oxygen), fluoro, OR5, C(O)R6, C(0)OR7, C(0)NRsR9,NR10Rn and N+R12R13R]4; and R2, rs and R4 independently represent (i.e. are the same or different) H, aryl, lower alkyl, lower alkenyl or lower alkynyl, the latter three of which are optionally substituted by one or more substituents selected from lower alkyl5 lower alkylene (optionally intemipted with oxygen), aryl, OR5, C(0)R6, C(0)OR7, C(0)NR8R9, NR10Rn and N RioRisR^ Zis-CHorN; yi, Y2, Y3 and Y4 are absent or independently represent aryl, lower alkyl, lower alkenyl or lower alkynyl, the latter three of which are optionally substituted by one or more substituents selected from lower alkyl, lower alkylene (optionally interrupted with oxygen), aryl, OR5, C(O)R6, C(0)OR7, C(O)NRSR9, NR10Rn and RisRu; and R5, R6, R7, R8, R9, rio, rh, Ri2, ris and R14 independently represent H or lower alkyl provided that at least one of Xh X2, X3 and X4 is a cationic group as defined above and at least one of X], X2, X3 and X4 is a hydrogen atom, a phenyl group, a lipophilic moiety, or a lower alkyl, alkaryl or aralkyl group. The term "lower alky!" is intended to include linear or branched, cyclic or acyclic, CrC20 alkyl which may be interrupted by oxygen (preferably no more than five oxygen atoms are present in each alkyl chain). Lower alkyl gi-oups which Rb R2, R3, R4, rs, Re, R?, rs, R-9, rio, rh, Ri2, ris and rh may represent include CrCiS all Thus, any one or more of ri to R^ (or of Xi to X4) may represent cyclic amine/ammonium gi'oups, for example: It will be appreciated that the cyclic amine/aminonium groups may also comprise fewer or greater than six members, for example such groups may comprise 4-, 5-, 7-, 8-, 9- or 10-membered rings. The term "lower alkylene" is to be construed accordingly. The terms "lower allcenyl" and "lower allcynyl" are intended to include linear or branched, cyclic or acyclic, C2-C20 allcenyl and allcynyl, respectively, each of which may be interrupted by oxygen (preferably no more than five oxygen atoms are present in each alkenyl or allcynyl chain). The term "lower alkenyl" also includes both the cis and trans geometric isomers. Lower allcenyl groups which Rh R2, R3, &4, R5, R6, R7, Rs, R9, rio, rh, Rn, ris and R]4 may represent include C2-CiS allcenyl, C2-, alkenyl, C2-C]6 alkeiryl, C2-C]4 allcen}'!, C2-Ci2 allcenyl, C2-C]0 alkenyl, C2-C8 alkenyL C2-C7 alkenyl, C2-C6 allcenyl, C2-C5 alkenyl, C2-C4 alkenyl, C2-Cs alkenyl and €3-04 allceiTyl. PrefeiTed lower alkenyl groups which ri, R2, R3, R4, rs, R$5 R7, RE, Rg, rio and Rn may represent include C2, C3, C4, C5, C6, C7, Cs, C9, C10> Cn, C12, C13 and C]4 allcenyl. The term "lower allcenylene" is to be construed according!)'. "Lower allcynyl" groups which Rls R2, R3, R4j R5, R6, R7j R8, R9, R10, Rn, Ri2, ris and rw may represent include C2-C1S allcynyl, C2-Ci6 alkynyl, C2-C]4 alkynyl, C2-C12 allcynyl, C2-C10 allcynyl, C2-C9 alkynyl, C2-CS alkynyl, C2-C7 allcynyl, C2-C6 allcynyl, C2-C5 allcynyl, C2-C4 allcynyl, C2-C3 allcynyl and C3-C4 allcynyl. Preferred lower allcynyl groups which ri, R2, R3, R4, R5, rg, R?, rs, rp, rio and Rn rnay represent include C2, C3, C4, C5> C6, C7, C8, C9, C10, Cn, C12, C13 and C14 alkynyl. The term "lower allcynjdene" is to be construed accordingly. The tenn "aryl" includes six to ten-rnembered carbocyclic aromatic groups, such as plienyl and naphthyl, which groups are optionally substituted by one or more substiruents selected from fluoro, cyano, nitro, lower alkyl (i.e. allcaiyl), OR5, C(O)R6j C(O)OR7j C(O)NRSR9 and The term "aralkyl" includes aryl groups joined to the porphyrin ring via a lower alkyl group. A second aspect of the invention provides a compound of formula II: wherein M is a metallic element or a metalloid element and Xi, X2, X3, X4, yi, Y23 ys, Y4 and Z are as defined above. The term "metallic element" is intended to include a divalent or trivalent metallic element. Preferably, the metallic element is diamagnetic. More preferably, the metallic element is selected from Zn (II), Cu (II), La (III), Lu (III), Y (III), In (III) Cd (II), Mg (II), A1(III)S Ru, Ni(II), Mn(IH), Fe(III) and Pd(II). Most preferably, the metallic element is N^II), Mn(in),Fe(III)orPd(n). The term "metalloid" is intended to include an element having physical and chemical properties, such as the ability to conduct electricity, that are intermediate to those of both metals and non-metals. The term metalloid element includes silicon (Si) and germanium (Ge) atoms which are optionally substituted with one or more ligands. It will be appreciated that the terms metallic element and metalloid element include a metal element or a metalloid element having a positive oxidation state, all of which may be substituted by one or more ligands selected from fluoro, OH, ORis wherein rjs is lower alk} i, lower alkenyl, lower alkynyl, aralkyl, aryl or alkaryl as defined above (wherein aryl and alkaryl are mono-substituted). The compounds of formulae I and II comprise at least one cationic group. Thus, the compounds of the invention may carry a net positive charge, for example a charge of +1, +2, +3, +4, +5, +6 or more. In a preferred embodiment, the compounds carry a net charge of less than +4, for example +1, +2 or +3. In a particularly preferred embodiment, the compounds cany a net charge of+2. It will be appreciated by persons skilled in the art that compounds of formulae I and II may be counterbalanced by counter-anions. Exemplary counter-anions include, but are not limited to, halides (e.g. fluoride, chloride and bromide), sulfates (e.g. decylsulfate). nitrates, perchlorates, sulfonates (e.g. methane sulfonate) and trifluoroacetate. Other suitable counter-anions will be well known to persons skilled in the art. Thus, pharmaceutically, and/or veterinarily, acceptable derivatives of the compounds of formulae I and II, such as salts and solvates, are also included within the scope of the invention, Salts which may be mentioned include: acid addition salts, for example, salts formed with inorganic acids such as hydrochloric, hydrobromic, sulfuric and phosphoric acid, with carboxylic acids or with organo-sulfonic acids; base addition salts; metal salts formed with bases, for example, the sodium and potassium salts. It will be further appreciated by skilled persons that the compounds of formula I may exhibit tautomerism. All tautomeric forms and mixtures thereof are included within the scope of the invention. Compounds of formulae I and II may also contain one or more asymmetric carbon atoms and may therefore exhibit optical and/or diastereoisomerism. Diastereoisomers may be separated using conventional techniques, e.g. chromatography or fractional crystallisation. The various stereoisomers may be isolated by separation of a racernic or other mixture of the compounds using conventional, e.g. fractional crystallisation or HPLC, techniques. Alternatively, the desired optical isomers may be made by reaction of the appropriate optically active starting materials under conditions which will not cause racemisation or epimeiisation, or by derivatisation, for example with a homochiral acid followed by separation of the diastereomeric esters by conventional means (e.g. HPLC, chromatography over silica). All stereoisomers are included within the scope of the invention. In a preferred embodiment of the compounds of the first and second aspects of the invention, Z is -CH. A characterising feature of the compounds of the first and second aspects of the invention is that at least one of substituent groups Xi, X2, X3 and X4 is a quaternary ammonium cationic group of the formula -L-R3-N^O^XRs)!:^., as defined above. Preferably, none of Xi, X2, X3 and X4 is an anilinium or a pyridinimn cationic group. In a preferred embodiment, Rj is an unsubstituted lower alkylene, lower alkenylene or lower allcynylene group. Advantageously, ri is a straight-chain lower alkylene group of formula: - (CH2)m~. Preferably, 'in' is an integer between 1 and 20. More preferably, 'm' is an integer between 1 and 10, for example between 1 and 6, between 1 and 5, between 1 and 4 or between 1 and 3. Preferred straight-chain lower alkylene groups which R] ma)' represent include groups of the above formula wherein in is 2, 3, 4, 5, 6, 7, 8, 9 or 10. Most preferably, 'm' is 2 or3. The remaining three substituent groups of the quaternary ammonium moiety, i.e. R2, R3 and R4, may be the same or different and are selected from H, lower alkyl, lower alkenyl or lower alkynyl, the latter three of which are optionally substituted by one or more substituents selected from lower alkyl, OR5? C(O)R6j C(0)OR7, C(O)NRSR9, NR10RH and N Ri2R]3Ri4. In a preferred embodiment, R2, R3 and/or R4 are lower alkyl, lower alkenyl or lower alkynyl group. Preferably, R2, R3 and/or R4 are unsubstituted lower alkyl groups. Optionally, at least one of R2, R3 and R* is an alkyl group which is substituted with a primary, secondary or tertiary amine group or a quaternary ammonium group. In a preferred embodiment of the compounds of the first and second aspects of the invention, Rj is -(0112)3—, R2 and R3 are CH3 and R4 is — (CH2)rN(CH3)2. In an alternative preferred embodiment of the compounds of the first and second aspects of the invention, ri is -(CH2)3-, and R2, R3 and R4 are eachCH3. In a further alternative preferred embodiment of the compounds of the first and second aspects of the invention, ri is -(CH2)3~, and R2j R3 and R4 are each CaHs- Advantageously,, at least one of Xls X2, X3 and X4 is a cationic group as defined above and at least one of X^ X2, X3 and X4 is a hydrogen atom. Preferably, each of Xl3 X2, Xs and X4 is a hydrogen atom or a cationic group as defined above. Conveniently, the pK values of any primary, secondary or tertiary amine groups, if present in the compounds of the invention, is greater than 8 to ensure that the group is protonated when in a physiological environment. The quaternary ammonium cationic group is optionally joined to the porphyrin ring via a linking moiety, L. Preferred linking moieties, L, include phenoxy, phenylene, sulfonyl amido, aminosulfonyl, sulfonylimino, phenylsulfonylamido, phenyl-aminosulfonyl, urea, urethane and carbamate linking moieties. In a preferred embodiment, the quaternary ammonium cationic group is joined to the porphyrin ring via a phenoxy linker. Thus, Xj, X2, X3 and/or X4 may have the following formula: wherein R is R] - N+(R2)(R3)R4, as defined above, and 'n' is an integer between 1 and 3. In an alternative preferred embodiment, the quaternary ammonium cationic group is joined to the poiprryrin ring via a phenylene linlcer. Thus, Xi, X2, X3 and/or X4 may have the following formula: wherein R is R] - N4(R2)(R3)R4. as defined above, and 'm' is an integer between 1 and 3. Preferably, 'm' is 2, and most preferably 1 . In an alternative preferred embodiment, Xi, X2, X3 and/or X4 may have the following formula: wherein R is Rj — N+(R2)(R3)R4- 'n' and 'm' are as defined above, and 'n + m' is between 1 and 3. Advantageously, L comprises a benzene ring (e.g. phenoxy, phenylene, phenylsulfonylamido or phenylamino-sulfonyl) mono-substituted at the para-position. Alternatively,, L may be mono- or di-substituted at meta-or ortho-positions. L may also be 'bothpara- and o/tAo-substituted. In an alternative preferred embodiment, the quaternary ammonium cationic group is joined directly to the porphyrin ring, i.e. L is absent. In a preferred embodiment of the first and second aspects of the invention, the compound comprises two cationic groups, as defined above, on opposite sides of the porphyrin ring, i.e. at ring positions 5 and 15 or ring positions 10 and 20. For example, Xi and Xs may be a hydrogen atom, a lipophilic moiety, a phenyl group, a lower alkyl, alkaryl or aralkyl group, and X2 and X4 may be cationic groups, or vice versa. Preferably, Xi and X3 are both a hydrogen atom and X2 and X4 are both a ca.tionic group, or vice versa. Alternatively, the compound of the invention may comprise two cationic groups, as defined above, on neighbouring positions of the porphyrin ring, i.e. at ring positions 5 and 10, or ring positions 10 and 15, or ring positions 15 and 20 or ring positions 20 and 5. For example, X! and X2 may be hydrogen and Xs and X4 may be cationic groups, or X2 and X3 may be hydrogen and X4 and Xj may be cationic groups, etc. It will be appreciated by persons skilled in the art that additional isorneric structural possibilities arise when Z represents nitrogen. Such possibilities are included within the scope of the present invention. In a further preferred embodiment of the compounds of the first and second aspects of the invention, the compound is substituted on one or more of its constituent pyrrole rings. Thus, yi, Y2, Y3 and Y4 may be absent or independently represent aryl, lower alkyl, lower alkenyl or lower alkynyl, the latter three of which are optionally substituted b}' one or more substituents selected from lower alkyl, lower alkyl ene (optionally interrupted with oxygen), aryl, OR5, C(0)R6, C(O)OR7, C(O)NR8RS, NRioRn and K^R^R^R^. It will be appreciated by skilled persons that yi, Y2, Y3 and/or Y4 may comprise cyclic groups, which may be saturated or aromatic. For example, one or more of the pyrrole rings may be substituted to form an iso-indole group, i.e. Yb Y2, Y3 and/or Y4 together with the pyrrole ring to which they are attached may be cyclic. In an alternative preferred embodiment of the compounds of the first and second aspects of the invention, Yl3 Y2, Y3 and Y4 are absent. Thus, the. porphyrin ring is preferably substituted only at one or more of positions 5, 10, 15 or 20. In a further preferred embodiment of the compounds of the first and second aspects of the invention, at least one of Xj, X2, X3 and X4 is or comprises-a lipophilic moiety. By 'lipophilic moiety' we include moieties having a partition coefficient between 1-n-octanol and water expressed as logP of greater than 1.0 at physiological pH and 25° C. Conveniently, the lipophilic moiety is a saturated, straight-chain alkyl group of formula — (CH2)PCH3, or an equivalent alkylene group of formula -(CH2)p-, wherein 'p' is an integer between 1 and 22, for example between 1 and 18. Preferably, 'p' is between 1 and 18, more preferably between 2 and 16, between 4 and 16, between 6 and 18, between S and 16 or between 4 and 12. Most preferably, 'p' is between 10 and 12. It will be appreciated that Xl3 X2, X3 and/or Xt may be a cationic group, as defined above, which also comprises a lipophilic moiety. In an alternative preferred embodiment of the first and second aspects of the invention, none of Xi, X2, X3 and X4 is a lipophilic moiety. Advantageously, the compounds of the invention are soluble in water. Preferably, the compounds may be dissolved in water to a concentration of at least 5 ju.g/1, for example at least 10 ju.g/1, 15 ug/1 or 20 fig/1. More preferably, the compounds may be dissolved in water to a concentration of at least 100 fig/1, for example 200 fig/1, 300 ug/1, 400 ug/1, 500 j.ig/1, 1 mg/rnl, 5 mg/ml, 10 ing/ml, 20 mg/ml, 50 rng/inl or 100 mg/ml, Conveniently, the compounds of the invention exhibit greater toxicity to a target microorganism (e.g. a bacterium) upon illumination/irradiation than in the absence of activating illumination/irradiation, i.e. they exhibit greater photodynamic activity ('light toxicity') than dark toxicity (see below). It will be appreciated that such toxicity may be determined using cell cultures. Preferably, the photodynamic activity of a compound is at least two-fold greater than the dark toxiciry of that compound, more preferably at least three-fold, at least four-fold, at least five-fold, at least six-fold, at least eight-fold, at least ten-fold, at least fifteen-fold or at least twenty fold. Most preferably, the compound of the invention is substantially non-toxic in the absence of illumination/irradiation. In a preferred embodiment, the compound of the invention is toxic to the target microorganism (e.g. bacterial cells) at low doses. Preferably, the compound is toxic to the target microorganism at a concentration of less than 10jiM5 for example less than 1 uM. less than 0.1 iiM, less than 0.01 uM, less than 0.005 uM or less than 0.001 uM (see Example B). * Preferred compounds of the invention include the following: (a) 5,15-bis-(4-{3-[(3-Dimethylaniino-propyl)-dimethyl-aimnonio]-propyloxy}-phenyl)-porphyrin dichloride ("Compound 5") Preferably, this compound is provided as a dichloride or tetrachloride salt. Preferably, tliis compound is provided as a dichloride salt. (b) 5,15-bis-[4-(3-Trietliylammonio-propyloxy)-phenyl]-porph}^rin dichloride ^'Compound ^"); (c) 5,15-bis-[3-(3-Trimethylarrmionio-propyloxy)-ph.enyl]-porphyriii dichloride ("Compound 12"}; Preferably, this compound is provided as a dichloride salt. (d) 5,15-bis-[4-(3-Trimethylammonio-propyloxy)-phenyl]-porphvrin dichloride ("Compound 10"); Preferably, this compound is provided as a dichloride salt. (e) 5-[3,5-bis-(3-Trimethylammoriio-propyloxy)-phenyl]-15-undecyl-porphyrin dichloride ("Compound 6""); Preferably, this compound is provided as a dichloride salt. (f) 5- {4-[3-Dimethyl-(3 -dimetli3'laniinopropyl)-ammoiiio-propyloxyjphenyl} -15-(4-dodecyloxy-plienyl)-porpliyiin ("Compound 23"); Preferably, this compound is provided as a chloride or dichloride salt. (g) 3-[({3-[(3-{4-[15-(4-Dodecyloxy-plienyl)-poiphyrin-5-yl]-• phenoxy} -propyl)-dimethyl-amrnonio]-propyl} -dimethyl-airrmonio)-propyl] -trimethyl-aixunonium trichloride ("Compound 25"); Preferably, this compound is provided as a trichloride salt. (h) 5,15-bis-[3 -(3-Tiimethylamrniiionio-propyloxy)-phenylJ-10-undecyl-porphyrin dichloride ^Compound 28"); Preferably, this compound is provided as a dichloride salt. (i) 5- {4-[3-Diiiiethyl-(3-trimethylamiiionio--propyl)-amrnonio- propyloxyj-phenyl}-15-(4-dodecyloxy-phenyl)-porphyrin dichloride ("Compound 31"); and Preferably, this compound is provided as a dichloride salt. (j) 5-[4-(3-Dimethyldecyl-amjiionioprop3'loxy)-phenyl]-l 5- {4-[3-dimeth}^l-(3-dimethylaminopropyl)-ammoniopropylox}']-plienyl}-porphyriii di chloride ("Compound 32"). Preferably, this compound is provided as a dichloride salt. It will be appreciated that the above compounds may alternatively be in a metallated form, i.e. they may comprise a chelated metallic element or metalloid element within the porphyrin ring. A third aspect of the invention provides a compound for use as a selective photodynamic therapy agent, i.e. for selectively killing microorganisms, wherein the compound is a compound according to the first or second aspect of the invention. By 'selective' we mean the photodynamic therapy agent is preferentially toxic to one or more microorganisms (such as bacteria, mycoplasmas, yeasts, fungi and/or viruses) compared to mammalian, e.g. human, host cells. Preferably, the toxicity of the compound to a target microorganism is at least two-fold greater than the toxicity of that compound to mammalian cells (such as human skin cells), more preferably at least three-fold, at least four-fold, at least five-fold, at least six-fold, at least eight-fold, at least ten-fold, at least fifteen-fold or at least twenty fold. Most preferably, the compound of the invention is substantially non-toxic to mammalian cells. In this way, when the compounds of the invention are used to treat bacterial infections, for example, dosing regimes can be selected such that bacterial cells are destroyed with minimal damage to healthy host tissue (e.g. skin cells). Thus, the photodynamic therapy agents preferably exhibit a 'therapeutic window'. A fourth aspect of the invention provides a pharmaceutical formulation comprising a compound according to the first or second aspect of the invention in admixture with a pharmaceutically or veterinarily acceptable adjuvant, diluent or earner. The compounds of the invention can be formulated at various concentrations, depending on the efficacy/toxicity of the compound being used and the indication for which it is being used. Preferably, the formulation comprises the compound of the invention at a concentration of between 0.1 uM and 1 mM, more preferably between 1 p.M and 100 uM, between 5 uM and 50 uM, between 10 jiM and 50 jiM, between 20 uM and 40 uM and most preferably about 30 juM. For in vitro applications, formulations may comprise a lower concentration of a compound of the invention, for example between 0.0025 uM and 1 uM. It will be appreciated by persons skilled in the art that the compounds of the invention will generally be administered in admixture with a suitable pharmaceutical excipient diluent or earner selected with regard to the intended route of administration and standard pharmaceutical practice (for ,th example, see Remington: The Science and Practice of Pharmacy, 19 edition, 1995, Ed. Alfonso Gennaro, Mack Publishing Company, Pennysylvania., USA). For example, for application topically, e.g. to the skin or a wound site, the compounds of the invention can be administered in the form of a lotion, solution, cream, gel, ointment or dusting powder (for example, see Remington, supra, pages 1586 to 1597). Thus, the compounds of the invention can be fonnulated as a suitable ointment containing the active compound suspended or dissolved in, for example, a mixture with one or more of the following: mineral oil, liquid petrolatum, white petrolatum, prop)'lene glycol, polyoxyethylene polyoxypropylene compound, emulsifying wax and water. Alternatively, they can be formulated as a suitable lotion or cream, suspended or dissolved in, for example, a mixture of one or more of the following: mineral oil, sorbitan monostearate, a polyethylene glycol, liquid paraffin, polysorbate 60, cetyl esters wax, e-lauryl sulphate, an alcohol (e.g. ethanol, cetearyl alcohol, 2-octyldodecanol, benzyl alcohol) and water. In a preferred embodiment, the formulation (e.g. lotion, solution, cream, gel or ointment) is water-based. Formulations suitable for topical administration in the mouth further include lozenges comprising the active ingredient in a flavoured basis, usually sucrose and acacia or tragacanth; pastilles comprising the active ingredient in an inert basis such as gelatin and glycerin, or sucrose and acacia; and mouth-washes comprising the active ingredient in a suitable liquid earner. The compounds of the invention can also be administered intranasally or by inhalation and are conveniently delivered in the form of a diy powder inhaler or an aerosol spray presentation from a pressurised container., pump, spray or nebuliser with the use of a suitable propellant, e.g. dichlorodiftuorornethane: trichlorofluoromethane, dichlorotetra-fluoroethane, a hydrofluoroalkane such as 1,1,1.2-tetrafluoroethane (HFA134A3 or 1,1,1,2,3,3,3-heptafluoropropane (HFA227EA3), carbon dioxide or other suitable gas. In the case of a pressurised aerosol, the dosage unit may be determined by providing a valve to deliver a metered amount. The pressurised container, pump, spray or nebuliser may contain a solution or suspension of the active compound, e.g. using a mixture of ethanol and the propellant as the solvent, which may additionally contain a lubricant, e.g. sorbitan trioleate. Capsules and cartridges (made, for example, from gelatin) for use in an inhaler or insufflator may be formulated to contain a powder mix of a compound of the invention and a suitable powder base such as lactose or starch. Aerosol or dry powder formulations are preferably arranged so that each metered dose or "puff contains at least 1 mg of a compound of the invention for delivery to the patient. It will be appreciated that he overall dose with an aerosol will vary from patient to patient and from indication to indication, and may be administered in a single dose or, more usually, in divided doses throughout the day. Alternatively, other conventional administration routes known in the art may also be employed; for example the compounds of the invention may be delivered orally, buccally or sublingually in the form of tablets, capsules, ovules, elixirs, solutions or suspensions, which may contain flavouring or colouring agents, for immediate-, delayed- or controlled-release applications. The compounds of invention may also be administered intra-ocularly (see below), intra-aurally or via intracavernosal injection. The compounds of the invention can also be administered parenterally, for example, intravenously, intra-arterially, iiitraperitoneally, intrathecaltyj intraventricularly, intrastemally, intracranially, intra­muscularly or subcutaneously (including via an array of fine needles or using needle-free Powderject® technology), or they may be administered by infusion techniques. They are best used in the form of a sterile aqueous solution which may contain other substances, for example, enough salts or glucose to make the solution isotonic with blood. The aqueous solutions should be suitably buffered (preferably to a pH of from 3 to 9), if necessary. The preparation of suitable parenteral formulations under sterile conditions is readily accomplished by standard pharmaceutical techniques well-known to those skilled in the art. Formulations suitable for parenteral administration include aqueous and non-aqueous sterile injection solutions which may contain anti-oxidants, buffers, bacteriostats and solutes which render the formulation isotonic with the blood of the intended recipient; and aqueous and non-aqueous sterile suspensions which may include suspending agents and thickening agents. The formulations may be presented in unit-dose or multi-dose containers, for example sealed ampoules and vials, and may be stored in a freeze-dried (lyophilised) condition requiring only the addition of the sterile liquid earner, for example water for injections, immediately prior to use. Extemporaneous injection solutions and suspensions may be prepared from sterile powders, granules and tablets of the land previously described. The compounds of the invention may also be administered by the ocular route, particularly for treating diseases of the eye. For ophthalmic use, the compounds of the invention can be formulated as micronised suspensions in isotonic, pH adjusted, sterile saline, or, preferably, as solutions in isotonic, pH adjusted, sterile saline, optionally in combination with a preservative such as a benzylalkonium chloride. Alternatively, they may be formulated in an ointment such as petrolatum. For veterinary use, a compound of the invention is administered as a suitably acceptable formulation in accordance with normal veterinary practice and the veterinary surgeon will determine the dosing regimen and route of administration which will be most appropriate for a particular animal. The compounds and/or formulations of the invention may be stored in any suitable container or vessel known in the art. It will be appreciated by persons skilled in the art that the container or vessel should preferably be airtight and/or sterilised. Advantageously, the container or vessel is made of a plastics material, such as polyethylene. A fifth aspect of the invention provides a compound according to the first or second aspects of the invention for use in medicine and., in particular, in the curative and/or prophylactic treatment of microbial infections. The compounds of the invention are photosensitive (photodynamic) as they emit reactive oxygen species, such as singlet oxygen or oxygen free radicals, following illumination/irradiation in the presence of oxygen with light of an appropriate wavelength (typically 400 nm to 800 run; see below). Consequently, the compounds of the invention are suitable for use as photodynamic therapy agents in the curative and/or prophylactic treatment of a medical condition for which a photodynamic agent is indicated (for example, see Smith, 2002, Curr Probl Cancer. 26(2):67-108; Hopper, 2000, Lancet Oncol. 1:212-9; Dougherty, 2002, J din Laser Med Surg. 20(1)3-7; Ceburkov & Gollnick, 2QQQ,EurJDermatol. 10(7):568-75). Preferably, the compounds of the invention are for use in the curative and/or prophylactic treatment of bacterial infections such as Gram positive cocci (e.g. Streptococcus), Gram negative cocci (e.g. Neisseria), Gram positive bacilli (e.g. Coiynebacterium species), Gram negative bacilli (e.g. Escherichia coli), acid-fast bacilli (e.g. a typical Mycobacteriuni) and including infections causing abscesses, cysts, dermatological infections, wound infections, arthritis, urinary tract infections, pancreatitis, pelvic inflammatory disease, peritonitis, prostatitis, infections of the vagina, oral cavity (including dental infectious), eye and/or ear, ulcers and other localised infections; actinomyces infections; fungal infections such as Candida albicans, Aspergillus and Blasiomyces; viral infections such as HIV, encephalitis, gastro-enteritis, haemorrhagic fever, hantavirus, viral hepatitis, herpesvims (e.g. cytornegalovirus, Epstein-Barr, herpesvirus simiae, lierpes simplex and varicella-zoster); protozoal infections such as amoebiasis, babesiosis, coccidiosis, cryptosporidiosis, giardiasis, Leishmaniasis, Trichomoniasis, toxoplasmosis and malaria; helminthic infections such as caused by nematodes, cestodes and trematodes, e.g. ascariasis, hookworm, lymphatic filariasis, onchocerciasis, schistosorniasis and toxocariasis; and inflammatory diseases such as soft-tissue rheumatism, osteoarthritis, rheumatoid arthritis and spondyloarthropathies. More preferably, the compounds of the invention are for use in the curative and/or prophylactic treatment of infections by Gram positive bacteria and/or Gram negative bacteria. Most preferably, the compounds of the invention are for use in the curative and/or prophylactic treatment of infections by Gram positive bacteria. The compounds of the invention are preferably used to kill microorganisms, e.g. bacteria, mycoplasmas, yeasts, fungi and viruses. The compounds of the invention are particularly suitable for killing bacteria which have developed resistance to conventional antibiotic treatments, such as methicillin-resistant^iap/zy/ococcMj aureus (MRSA). It will be appreciated by persons skilled in the art that the compounds of the invention are suitable to treat all infections where target microorganisms can be found on a light-accessible surface or in a light accessible area (e.g. epidermis, oral cavity, nasal cavity, sinuses, ears, eyes, lungs, uro-genital tract., and gastrointestinal tract). In addition, the compounds of the invention are suitable to treat infections on surfaces or areas which are made accessible to light transiently, such as infected bones temporarily exposed during surgical procedures. Infections of the peritoneal cavity, such as those resulting from burst appendicitis are light-accessible via at least laparoscopic devices. Dosages of the compound of the invention will depend on several factors; including the particular compound used, the formulation, route of administration and the indication for which the compound is used. Typically, however, dosages will range from 0.01 to 20 mg of compound per kilogram of body weight, preferably from 0.1 to 15 mgfkg, for example from 1 to 10 mg/kg of body weight. In a preferred embodiment the compounds of the invention are used in combination with conventional antimicrobial agents. For example, the compounds may be used in combination with one or more of the following conventional antibiotics: anti-bacterial agents, for example natural and s^Tithetic penicillins and cephalosporins, sulphonamides3 erythromycin, kanomycin. tetracycline, cHoramphenicol, rifampicin and including gentamicin, ampicillin, benzypeniciUin, benethamine penicillin, benzathine penicillin, phenethicillin, phenoxy-methyl penicillin, procaine penicillin, cloxacillin, flucloxacillin, methicillin sodium, amoxicilrin, bacampicillin hydro chloride, ciclacillin, mezlocillin, pivampicillin, talampicillin hydrochloride, carfecillin sodium, piperacillin, ticarcillin, mecillinam, pirmecillinan, cefaclor, cefadroxil, cefotaxime, cefoxitin, cefsulodin sodium, ceftazidime, ceftizoxime, cefuroxime, cephalexin, cephalothin, cephamandole, cephazolin, cephradine, latamoxef disodium, aztreonam, chlortetracycline hydrochloride, clomocycline sodium, demeclocydine liydrochloride, doxycycline, lymecycline, rninocycline,, oxytetracycline, amikacin, framycetin sulphate, neomycin sulphate, netilmicin, tobramycin, colistin, sodium fusidate, polymyxin B sulphate, spectinomycin, vancomycin, calcium sulphaloxate, sulfametopyrazine, sulphadiazine, sulphadimidine, sulphaguanidine, sulphaurea, capreomycin, metronidazole, tinidazole, cinoxacin, ciprofloxacin, nitrofurantoin, hexamine, streptomycin, carbenicillin, colistimethate, polymyxin B, furazolidone, nalidixic acid, trimethopiim-sulfamethox-azole, clindamycin, lincomycin, cycloserine, isoniazid, ethambutol, ethionamide, pyi-azinamide and the like; anti-fungal agents, for example miconazole, ketoconazole, ifraconazole, fluconazole, amphotericin, flucytosine, griseofulvin, natamycin, nystatin, and the like; and anti-viral agents such as acyclovir, AZT, ddl, amantadiiie liydrochloride, inosine pranobex, vidarabine, and the like. In a further preferred embodiment, the compounds of the invention are •-administered with penetration enhancing agents, such as poly- co (ethyleneirnine), or antibiotic agents which exhibit such penetration-enhancing capability (e.g. polynryxin or colistin). The compounds of the invention are particularly suited for use in the curative or prophylactic treatment of one or more of the following indications: Impetigo Impetigo is a highly communicable infection. It is the most common infection in children. Impetigo have two classic forms nonbullous and bullous. The nonbullous impetigo, also named impetigo contagiosa accounts for approximately 70% of cases. Lesions normally resolve in 2 to 3 weeks without treatment. Impetigo also may complicate other skin diseases such as scabies, varicella, atopic dermatitis, and Darier's disease. (a) Nonbullous Impetigo Type of bacteria Nonbullous is an infection caused principally by Group A beta-haemolytic streptococci (Streptococcus pyogenes), Staphylococcus aurens, or a combination of these two organisms (see Andrews' diseases of the skin: clinical dermatology 9th ed. (2000) edited by Odom RB editor Saunders p.312-4). Non-Group A (Group B, C, and G) streptococci may be responsible for rare cases of impetigo, and Group B streptococci are associated with impetigo in the newborn. 'NoiibuUous is a superficial, intraepidennal, unilocular vesiculopustular infection. Lesions of non bullous impetigo commonly begin on the skin of the face or extremities following trauma. As a rule, intact skin is resistant to impetiginazation. The clinical presentation of impetigo evolves in an orderly fashion from a small vesicle or pustule, which progresses into honey-coloured crusted plaque. Lesions usually are less than 2 cm in diameter. Lesions tend to dry, leaving fine crusts without cicatrisation. Lesions are usually minimally symptomatic. Rarely, erythema associated with mild pain or slight pruritus may be present. The infection spreads to contiguous and distal areas through the inoculation of other wound from scratching. Site of bacteria Nonbullous impetigo is a superficial streptococcal or staphylococcal infection which is localised to the subcorneal (just beneath the stratum corneum) layer of the skin (see Figure 1). More particular!}'., infection in impetigo is confined histopathogically to highly differentiated, upper epidermal keratinocytes. Once the bacteria invade a break in the sldn, they begin to multiply. The histopathology is that of an extremely superficial inflammation about the funnel-shaped upper portion of the pilosebaceous follicles. A subcorneal vesicopustule is formed, containing a few scattered cocci, together with debris of polymorphonuclear leukocytes and epidermal cells. In the dermis. there is a mild inflammatory reaction - vascular dilatation, oedema, and infiltration of polymorphonuclear leukocytes (Andrews' diseases of the skin, supra.,p.312-4). (b) Bullous impetigo Type of bacteria Bullous impetigo is caused primarily by strains of Staphylococcus aureus which produce exfoliative toxins (Sadick et al., 1997, Dermatologic Clinics 15(2): 341-9). Type of'wounds Bullous impetigo is Mstologically characterised by subcorneal cleavage and infiltrate with polymorphonuclear leucocytes migrating through the epidermis and accumulating between granular and stratum corneum skin layers. Small or large superficial fragile bullae are present on the trunk and extremities. Flaccid bullae and moist erosions with surrounding erythema are characteristic of this subcorneal infections. Often, only the remnants of ruptured bullae are seen at the time of presentation. The separation of the epidermis is due to an exotoxin produced by Staphylococcus aureus. Sites of bacteria Bullous impetigo is a superficial staphylococcal infection that occurs in and just beneath the stratum corneum (see figure 1). Bullous impetigo is considered due 10 exfoliaiive toxin produced by some Staphylococcus aureus attached to stratum comeum cell-. Atopic dermatitis (AD) Atopic dermatitis, also named atopic eczema, is a chronic inflammation of the skin resulting in an itchy rash, especially in the flexures i.e. behind the knees, in front of the elbows, wrists, neck, and eyelids. Infection of the rash is common, and causes further inflammation and itch. Eczema typically manifests in those aged 1-6 months. Approximately 60% of patients have their first outbreak by 1 year and 90% by 5 years. Onset of atopic dermatitis in adolescence or later is uncommon and should prompt consideration of another diagnosis. Disease manifestations vary with age. Type of bacteria Bacteria and their superantigens contribute to the pathogenesis of AD. Staphylococcus aureus colonises the skin of 90% of AD patients (chronic eczematous lesions) and only 5% of non-atopic patients. The colonisation density of Staphylococcus aureus can reach up to 107 colony rforming units cm" without clinical signs of infection in patients with AD. In addition, the apparently normal non-lesional skin of atopic patients contains increased numbers of Staphylococcus aureus. The reason for the overgrowth of Staphylococcus aureus in atopic dermatitis, though much less severely or not at all in diseases such as psoriasis, is not known. Protein A elicits a much less vigorous response in atopies than in normals or psoriatics, but this may be the result rather than a cause of colonisation. Attention has recently turned to the skin lipids and there is some evidence that fatty acids which may control staphylococcal colonisation are deficient in atopies. Superantigens are a unique group of proteins produced by bacteria and viruses that bypass certain elements of the conventional, antigen-mediated immune sequence. Whereas conventional antigens activate approximately 0.01% to 0.1% of the body's T cells, a superantigen has the ability to stimulate 5% to 30% of the T-cell population. S. aureus may exacerbate or maintain skin inflammation in AD by secreting a group of exotoxins that act as superantigens. AD patients possess an altered skin barrier secondary to an insufficiency of ceramides within the stratum corneum. It has been proposed that penetration of the skin by these exotoxins may cause activation of T cells, macrophages, LCs, and mast cells, thereby leading to the release of cytokines and mast cell mediators. It is conceivable that these events may provide the basis for inflammation in chronic AD. Speculation remains whether S. aureus colonisation and local superantigen secretion is a primary or secondary phenomenon in AD (Andrews' diseases of skin, Chap, 5, Atopic Dermatitis, Eczema, and non-infectious immunodeficiency disorders, p.69-76). Cutaneous viral, fungal, and bacterial infections occur more commonly in AD patients. Viral infections are consistent with a T cell defect and include herpes simplex (local or generalised, i.e. eczema herpeticum), molluscum contagiosum, and human papilloma virus. Superficial fungal infections with Trichophyton rubrum and Pityrosporon ovale also occur frequently. Bacterial infections, specifically those with S, aureus, are extremely common. Superinfection results in honey-coloured crusting, extensive serous weeping or folliculitis. Type of wounds Acute lesions appear as erymematous papules, vesicles, and erosions; chronic disease consists of fibrotic papules and thickened, lichenified skin. A finding of increasing numbers of pathogenic staphylococci is frequently associated with weeping, crusting, folliculitis and adenopathy. Secondary staphylococcal infection is frequent and local oedema and regional adenopatliy commonly occur during atopic dermatitis. Impetigo can be a sort of secondary infection of atopic dermatitis. The histology of atopic dermatitis ranges from acute spongiotic dermatitis to lichen simplex chronicus, depending on the morphology of the skin lesion biopsied. Sites of bacteria Staphylococcus aureus cell walls exhibit receptors, the so-called adhesins, for epidermal and dermal fibronectin and fibrinogen. It has been demonstrated that the binding of Staphylococcus aureus was mediated by fibrinogen and fibronectin in AD patients. As the skin of AD patients lacks an intact stratum corneum, dermal fibronectin might be uncovered and increase the adherence of Staphylococcus aureus. Fibrillar and amorphous structures have been traced between Staphylococcus aureus cells and corneocytes and may results in a bacterial biofilm. It has been observed that Staphylococcus aureus penetrates into intracellular spaces suggesting that the skin surface lipids are deteriorated in AD patients (see Breuer K et aL, 2002, British Journal of Dermatology 147: 55-61) . Ulcers Skin ulcers, such as diabetic foot ulcers, pressure ulcers, and chronic venous ulcers, are open sores or lesions of the skin characterised by the wasting away of tissue and sometimes accompanied by formation of pus. Skin ulcers may have different causes, and affect different populations, but they all tend to heal very slowly, if at all, and can be quite difficult and expensive to treat. Type of bacteria Superficial pressure ulcers are not associated with major infection problems. Aerobic microorganisms at low levels will contaminate pressure ulcers, but will not impede timely healing. However, deep full-thickness pressure ulcers can become secondarily infected, and osteomyelitis can occur. Those pressure ulcers with necrotic tissue contain high levels of aerobic and anaerobic microorganisms as compared to non-necrotic ulcers; foul smell is usually present when anaerobes invade the tissues. Thus, a treatment strategy is to clear necrotic tissue from the wound, producing a decrease in anaerobe presence. The infections of pressure ulcers are typically polymicrobial and can contain Streptococcus pyogenes, enterococci, anaerobic streptococci, Enterobacteriaece, Pseudomonas aeruginosa, Bacteroides fragilis and Staphylococcus aureus. Type of wounds Stage I pressure ulcer: Nonblanchable erythema of intact skin, considered to "be heralding lesion of skin ulceration. Stage IT pressure ulcer: Partial thickness skin loss involving the epidermis and/or dermis. The ulcer is superficial and presents clinically as an abrasion, blister, or shallow crater. Because the epidermis may be interrupted by an abrasion, blister, or shallow crater, the ulcer should be evaluated for signs of secondary infections. Stage III: Full thickness skin loss involving damage or necrosis of subcutaneous tissue which may extend down to, but not through, underlying fascia. The ulcer presents clinically as a deep crater with or without undermining of adjacent tissue. Stage IV: Full thickness skin loss with extensive destruction, tissue necrosis, or damage to muscle, bone, or supporting structures, such as tendons or joint capsules. Sites of bacteria There are three microbiological states that are possible in a wound: contamination, colonisation and infection. Contamination is characterised as the simple presence of microorganisms in the wound but without proliferation. It is generally accepted that all wounds, regardless of aetiology, are contaminated. Colonisation is characterised as the presence and proliferation of microorganisms in the wound but without host reaction. Colonisation is a common condition in chronic wounds such as venous ulcers and pressure ulcers and does not necessarily delay the healing process. -When bacteria invade healthy tissues and continue to proliferate to the extent that their presence and by-products elicit or overwhelm the host immune response, this microbial state is known as infection. The classic signs and symptoms of infection include local redness, pain and swelling, fever and changes in the amount and character of wound exudates. Lung infections The compounds of the invention are also suitable for treating a patient having an infectious disease of the lung, by administering to the subject a compound of the invention and irradiating (i.e. illuminating) the lung with light having a wavelength that causes the compound to produce an anti-microbial effect. Lung infection can occur with a variety of bacterial genera and species, which include Mycobacterium tuberculosis (tuberculosis), Pseudomonas (primary cause of death of cystic fibrosis patients), Streptococcus, Staphylococcus pneumoniae, Klebsiella, Toxoplasma, etc. Lung infection can also occur with a variety of virus strains and opportunistic pathogens (fungi, parasites). As pathogens of the lung are increasingly resistant to classical antibiotic therapies, photodynamic therapy offers an alternative method for eliminating these hamiful organisms. The compound of the invention can be administered to the lung in a variety of ways. For example the compound can be administered b}' the respiratory tract (i.e. intra-tracheally, intra-broncliially, or intra-alveolarly) or through the body wall of the chest. The light source can be applied through these routes as well with the help of flexible fibre optics for example. The illumination/irradiation can be directed to the base of the lung, to the apex of the lung, or both. Further indications The compounds of the invention are also suitable for the curative and/or prophylactic treatment of the following: Infections of burn sites and slcin grafts; otitis (ear infection), bacterial conjunctivitis and other eye infections, periodontitis and other dental infections, and infected bones exposed during surgical procedures. Thus, further aspects of the invention provide the following: (i) Use of a compound of the invention in the preparation of a medicament for use in photodynamic therapy; (ii) Use of a compound of the invention in the preparation of a medicament for lolling and/or preventing growth of microorganisms, such as bacteria, yeasts, fungi and viruses (for example, the medicament may be used to prevent or reduce the spread or transfer of that pathogen to other subjects, e.g. patients, healthcare workers, etc.}; (ill) Use of a compound of the invention in the preparation of a medicament for the curative and/or prophylactic treatment of a dermatological infection; (iv) Use of a compound of the invention hi the preparation of a medicament for the curative and/or prophylactic treatment of an infection of the lungs; (v) Use of a compound of the invention in the preparation of a medicament for the curative and/or prophylactic treatment of a wound infection and/or an ulcer; (vi) A method for treating a patient in need of treatment with a photodynamic therapy agent comprising administering to the patient a compound of the invention and illuminating/irradiating the compound; and (vii) A method for preventing wound infection comprising contacting the wound with a compound of the invention and illuminating/irradiating the compound (such that a reactive oxygen species is generated). In use, the photosensitive compounds of the invention are illuimnated/irradiated, i.e. activated, using conventional techniques known in the field of photodynamic therapy. Preferably, the compounds are illuminated/irradiated at a wavelength of between 400 nm and 800 nm. More preferably, the compounds are illuminated/irradiated at a wavelength corresponding to one or more of the absorption windows for porpliyrin, which lie at around 417 run (Soret band), 485 nm, 515nm, 550 nm, 590 nm and 650 nm. Most preferably, the compounds are illuminated/irradiated at a wavelength of about 417 inn. The optimal wavelength will depend on the particular compound and the indication for which is being used. For example, for impetigo, a wavelength of 510 to 560 nm is preferred due to the lesion colour. For open wounds, a wavelength of 560 to 700 is preferred, with preference towards the higher wavelength, in order to minimise activation of haemoglobin (mininium at 690 nm). It will be appreciated by persons skilled in the art that illumination/ irradiation may take place at various time points after application of the compound of the invention. Typically, the compound is illuminated/ irradiated between 5 minutes and 24 hours after application, for example, between 5 minutes and 2 hours or between 10 minutes and 1 hour. Optimal illumination times may be determined by experimentation. Where the compound of the invention is applied to the skin, the wavelength of light can be selected so as to control the depth of penetration. For example, for deep penetration longer wavelengths are preferred. Light intensity and overall light dose may also be varied to control the depth of penetration. Preferably, the photo dynamic therapy agent only penetrates the stratum cornewn. Likewise, the optimal duration of the exposure of the compound to illumination/radiation will depend on the particular compound and the indication for which is being used. Typically, however, the illumination time is between 1 and 30 minutes, more preferably between 5'and 20 minutes, for example 10 minutes. The total amount of illumination/radiation will vary according to the treatment and localisation of the tissues to be treated. Generally, the amount of illumination/radiation is between 10 and 1000 J/crn2, preferably between 10 and 350 J/cm2. Suitable light sources include the PDT 450L, PDT 650L and PDT 1200 lamps from Waldrnann AG, Germany. Alternatively, white light may be used for compound activation. The compounds of the invention may also be used to kill microorganisms in vitro. Thus, a further aspect of the invention provides a sterilising solution comprising a compound according to the first and/or second aspects of the invention. The solution may also take the form of a handwash or a concentrate to be diluted prior to use. Preferably, the compound of the invention is present in solution at a concentration of 1 to 100 (j.g/ml. Preferably, the solution further comprises a surface-active agent or surfactant. Suitable surfactants include anionic surfactants (e.g. an aliphatic sulphonate), amphoteric and/or zwitterionic surfactants (e.g. derivatives of aliphatic quaternary ammonium., phosphonium and sulfonium compounds) and nonionic surfactants (e.g. aliphatic alcohols, acids, amides or alkyl phenols with alkylene oxides) Conveniently, the surface-active agent is present at a concentration of 0.5 to 5 weight percent. The sterilising solutions of the invention are particularly suited for use in hospital environments. For example, the sterilising solutions may he used to sterilise surgical instruments and surgical theatre surfaces, as well as the hands and gloves of theatre personnel. In addition, the sterilising solutions may he used during surgery, for example to sterilise exposed bones. In all cases, the solution is applied to the surface to be sterilised and then illuminated/irradiated so as to produce a reactive oxygen species (see above) Thus, a further aspect of the invention provides a method for killing microorganisms in vitro comprising contacting the microorganisms to be killed with a compound of the invention and illuminating/irradiating the compound. Preferred, non-limiting embodiments of the invention will now be described by way of example, with reference to the accompanying drawings in which: Figure 1 shows a schematic diagram of the structure of skin. Figure 2 shows the growth inhibition (%) of (A) S. aureus BAA-44 cells and (B) E. coli ATCC 25922 cells illuminated with white light n (150 mW/cm ) for 0 or 30 minutes following pre-incubation for 5 minutes with a test compound at a concentration of 3 jiM. Figure 3 shows hacterial survival (cell number) of (A) S. aureus BAA-44 and (B) E. coli ATCC 25922 cells after incubation with a test compound at a concentration of 0.1 uM and illumination with light ('light toxicity', i.e. photodynamic activity) or no illumination ('dark toxicity'). Figure 4 shows the photodynamic activity (open bars) and dark toxicity (shaded bars) of (A) 'Compound 8" and (B) 'Compound W against S. aureus BAA-44 at varying doses. Figure 5 shows the effects of sodium azide (50 mM) and D2O on human dermal fibroblast (NHDF) cells incubated with Compound 10, with and without illumination using a light source (236, Waldmann). Triangles/solid line: Compound 10 + PBS buffer + light; Squares/solid line: Compound 10 + D2O + light; Circles/solid line: Compound 10 + sodium azide + light; Triangles/dotted line: Compound 10 + PBS buffer w/o light; Squares /dotted line: Compound 10 + D20 w/o light; Circles /dotted line: Compound 10 + sodium azide w/o light. (n=3, mean ± Std). Figure 6 shows the absence of resistance build-up by S. aureus BAA-44 following repeated treatments with Compound 10. Data shown as mean with 95% confidence limit error bars. Figure 7 shows a comparison of survival of clones exposed nine times to PDT treatments with Compound 10 and naive, untreated clones. Figure 8 shows the toxicity of 'Compound 8' against human fibroblasts (shaded bars) and S. aureus BAA-44 (open bars) at varying doses. Figure 9 shows a dimensional drawing of a 236 light source (Waldmann). Figure 10 shows photobleaching of 10 fiM Compound 10 illuminated for various times with blue light at (A) 15 mW/cm2 and (B) 150 mW/cm2. Figure 11 shows the chemical stability of Compound 10 formulated (A) as a solid, (B) in water and (C) in PBS. Figure 12 shows a 3D plot of the stability (measured by HPLC) of Compound 10 after 21 days in PBS buffer. Figure 13 shows the stability over 8 weeks of various formulations of (A) Compound 1, (B) Compound 8, (C) Compound 12 and (D) Compound 10. Figure 14 shows the extended stability over 17 weeks of various formulations of (A) Compound 10 and (B) Compound 8. Figure 15 shows the intracellular fluorescence distribution of NHDF cells incubated following co-staining with (A) lysosomal-specific dye LysoTracker Green (green) and (B) mitochondrial-specific dye Rhodamine G6 (red). Figure 16 shows the intracellular fluorescence distribution of NHDF cells incubated with 1 uM Compound 10 for 1 hour following co-staining with (A) mitochondria-specific Rhodamine G6 and (B) lysosomal-specific dye LysoTrackerGreen. Compound 10 fluorescence is localised extra-nuclearly and co-staining with mitochondria-specific Rhodamine G6 resulted in co-localisation of Compound 10 and fluorescence of mitochondria. Co-localisation is merged in yellow fluorescence. Co-staining with lysosomal-specific dye LysoTrackerGreen resulted in different localization of Compound 10 (red) and lysosomal fluorescence (green) (Figure 16B). Co-localisation is represented by yellow fluorescence. EXAMPLES example A: synthesis of exemplary compounds Materials and Methods NMR-measurements Proton NMR spectra were recorded on a Bruker B-ACS60 (300 MHz) instalment using TMS as internal standard. The chemical shifts are given in ppm and coupling constants in Hz in the indicated solvent. Some abbreviation for NMR: singlet (s), broad singlet (bs), doublet (d), triplet (t), quartet (q), quintet (quint), multiplet (m). Chemicals All solvents and reagents were purchased from Aldrich, Fluka, Merck and Lancaster and used without further purification. DipyiTolmethane was prepared as described by C. Briicker et aL, J. Porphyrins Phthalocyanines, 2 455 (1998). Chromatography Column chromatography was carried out using silica gel (Merck Silicagel 60, Fluka 60, 0.040-0.063 mm) and Sephadex LH-20 (Pharmacia). All solvents (Synophann) for chromatography were technical pure grade. Abreviations DDQ: 2i3-dichloro-5,6-dicyano-p-benzoquinone DMF: A^-dimethylformamide TFA: trifluoroacetic acid Synthesis routes for test compounds The following test compounds were synthesised: Exemplary compound's of the invention Compounds 6, S to 10, 12, 23, 25,28, 31 and 32. Reference compounds (for use as comparative controls) Compounds 1, 3, 16, 19, 26, 29, 33, 36, 37, 39, 41 and 46 to 51. Chemical intermediates Compounds 2, 4, 5, 7, 11, 13 to 15, 17, 18, 20 to 22, 24, 27, 30, 34, 35, 38,40 and 42 to 45. COMPOUND 1 5,10,15,20-tetrakis-[4-(3-Triniethylammonio-propyloxy)-phenyl]- poiphyrin tetrachloride To a vigorously-stirred suspension of 5,10,15,204etralds-(4-hydroxy-phenyl)-porphyrin (50 mg, 0.07 mmol) and K2C03 (230 mg, 1.7 mraol) in DMF (20 mL), a solution of (l-bromopropyl)-trimetliylammonium bromide (0.27 g, 1.05 mmol) in DMF (5 mL) is added dropwise at 50°C during 30 mins. The mixture is stirred at 50°C for 15 h. After removal of DMF under reduced pressure, the residue obtained is dissolved in metlianol (5 mL) and filtered through a pad of silica gel (depth 2 cm) supported on a steel frit (diameter 3.5 cm). After washing with methanol (1 L), the pad is eluted with acetic acid. After evaporation of solvent from the eluate, the residue obtained is purified by chromatography on a column (2.5 x 40 cm) of Sephadex LH20 eluting with n-butanol:water:acetic acid (4:5:1, by vol., upper phase). The recovered material is dissolved in the minimum volume of methanol and the solution is passed through a short column (3.5 x 20 cm) of anion exchange resin (Amberlite IRA 400, chloride form). The recovered tetrachloride salt is dried under high vacuum and obtained as violet crystals. ]H-NMR: oh (300MHz, CD3OD): 2.35-2.50 (bs, 8 H), 3.25-3.35 (bs, 36 H), 3.65-3.75 (bs, 8 H), 4.35 (m, 8 H), 7.30, 8.10 (2 x d, 3J 8.5 Hz, 16 H), 8.80-9.00 (bs, 8 H). COMPOUND 2 5,10,15-tris-(4-Hydroxy-phenyl)-20-(4-undecyloxy-phenyl)-porphyrin To a vigorously-stirred suspension of 5,10,15,20-tetrakis-(4-hydroxy-phenyl)-poiphyrin (400 mg, 0.59 minol) and K2C03 (1.0 g, 7.1 inmol) in DMF (75 mL), a solution of 1-bromoundecane (0.1 mL, 0.45 mmol) in DMF (10 mL) is added dropwise at 50°C during 30 mins and the mixture is stirred at the same temperature for 1.5 h. After removal by filtration of K2C03 and removal under reduced pressure of DMF, the residue obtained is dissolved in dichloromethane (200 mL), washed with water (3x150 mL) and the solution dried (Na2SC>4). The solvent is evaporated under-reduced pressure and the residue obtained is dissolved in toluene :ethanol (5:1 by vol., ca. 10 mL) and purified by chromatography using a column (5 X 50 cm) of silica gel (Merck 60). The column is eluted with toluene followed by toluene:ethyl acetate (2:1 by vol.) and the desired material recovered by evaporation of solvent from the appropriate fractions is dried under high vacuum. The product is obtained as violet crystals. !H-NMR: 5H (SOOMz, d6-acetone): 0.95 (t, 3J7.5 Hz, 3 H), 1.25-1.55 (m, 14 H), 1.58 (quint, 1/7.5 Hz,, 2 H), 1.85 (quint, 3J7.5 Hz, 2 H), 4.16 (t, 3/7.5 Hz, 2 H), 7.20 (d, 3/8.1 Hz, 2 H), 7.25 (d, l/S.2 Hz, 6 H), 8.00-8.15 (m, 8 H), 8.80-9.10 (m, 8 H). COMPOUND 3 5,10., 15-tri.s-[4-(3-Trimethylaminonio-propyloxy)-phenyl]-20-(4- undecyloxy-plienyl)-porphyrin trichloride To a vigorously-stirred suspension of Compound 2 (100 mg, 0.12 rnmol) and K2C03 (230 mg, 1.7 mmol) in DMF (30 mL), a solution of (1-bromopropyl)-trimethylammonmm bromide (0.3 g, 16.6 mmol) in DMF (10 mL) is added at 50°C and the mixture is stirred at this temperature for 12 h. After removal of the DMF under reduced pressure, the residue obtained is dissolved in methanol (5 mL) and filtered through a pad of silica gel (depth 2 cm) supported on a steel frit (diameter 3.5 cm). After washing with methanol (ca. 1L), the pad is eluted with acetic acid:methanol:water (3:2:1, by vol.). After evaporation of the solvent from the eluate under reduced pressure, the residue obtained is purified by chromatography on a column (2.5 x 40 cm) of Sephadex LH-20 eluting with n-butanol:water:acetic acid (5:4:1, by vol., upper phase). After removal of the solvent from appropriate fractions of the eluate under reduced pressure, the residue obtained is dissolved in methanol (5 mL) and the solution is passed through a short column (3.5 x 20 cm) of anion exchange resin (Amherlite IRA 400, chloride form). The final product is obtained as the trichloride salt, after removal of solvent and drying under high vacuum, as violet crystals. ]H-NMR: 5H (300MHz, CD3OD): 0.80 (t, 3J 7.5 Hz, 3 H), 1.15-1.45 (m, 16 H), 1.50-1.60 (bs, 2 H), 2.25-2.45 (bs, 6 H), 3.25-3.35 (bs, 27 H), 3.75-3.85 (bs, , 6 H), 4.18 (t, 3J7.5 Hz, 2 H), 4.40-4.45 (bs, 6 H), 7.20-7.40, 7.95-8.15 (2 x m, 16 H), 8.60-9.00 (bs, 8 H). COMPOUND 4 5 -(3,5 -Dimethoxy-phenyl)-15-undecyl-porphyrin To a stirred solution of dipyrrolemethane (0.62 g, 4.2 rnrnol) in dichloromethane (5 mL) is added 3,5-dimethoxybenzaldehyde (0.35 g, 2.1 mmol) and dodecanal (0.464 g, 2.52 mmol) in degassed dichloromethane (1L). TFA (0.07 mL, 3.0 mmol) is added dropwise. The solution is stirred at room temperature in the dark for 17 h under argon. After addition of DDQ (2.7 g, 12 mmol), the mixture is stirred at room temperature for a further hour. Purification of material recovered after removal of solvent under reduced pressure by chromatography on a column (400 g) of silica gel (Merck 60) with toluene for elution yields the product as violet crystals. 'H-NMR: 5H (300Mz,.CDCl3): 0.80 (t, 1/7.5 Hz, 3 H), 1.10-1.25 (m, 12 H), 1.40 (m, 2H), 1.75 (quint,, 3/7.5 Hz, 2 H), 2.45 (quint, V 7.5 Hz, 2 H), 3.90 (s, 6H), 4.90 (t, 1/7.5 Hz, 2 H), 6.80 (m, 1 H), 7.35 (m, 2 H), 9.00, 9.25, 9.30, 9.50 (4 x d,, 3/4.7 Hz, 4 x 2 H), 10.15 (s, 2H). COMPOUND 5 5-(15-Undecyl-porphyrin-5-yI)-benzene-l,3-diol To a solution of Compound 4 (80 mg, 0.133 mmol) in anhydrous dichloromethane (80 mL) under an argon atmosphere, BBr3 (5 mL, 1M in dichloromethane) is added dropwise at —70°C and the mixture is stirred for 1 h at this temperature and then warmed to room temperature and stirred overnight. The mixture is cooled to -10°C and hydrolysed by the addition of water (2 mL) and stirring for 1 h. NaHC03 (3 g) is added directly for neutralisation. The mixture is stirred for a further 12 h and after filtration of NaHCOs and removal of dichoromethane under vacuum the residue obtained is purified by column chromatography using silica gel eiuting with dichloromethane. After evaporation of solvent from appropriate combined fractions and drying of the residue obtained under high vacuum the product is obtained as violet crystals 'H-NMR: SH (SOOMz, d6-acetone): 0.75 (t, V7.5 Hz, 3 H), 1.05-1.25 (m, 12 H), 1.30-1.40 (m, 2H), 1.45-1.50 (m, 2 H), 2.40 (quint, 3/7.5 Hz, 2 H), 4.90 (t, 3J 7.5 Hz, 2 H), 6.65 (m, 1 H), 7.18 (m, 2 H), S.60-S.65, 9.00-9.05, 9.35-9.40, 9.55-9.60 (4 x m, 8 H), 10.25 (s, 2H). COMPOUND 6 5-[335-bis-(3-Trimefhylanimonio-prop)^loxy)-phenyl]-15-undecyl-porpbyrin dichloride To a vigorously-stirred suspension of Compound 5 (80 mg, 0.14 nunol) and K2C03 (230 mg, 1.7 rnmol) in DMF (30 mL) is added (1-bromopropyl)-trimetliylammonium bromide (0.3 g, 16.6 mmol) at 50 °C. The mixture is stirred at this temperature for IS h. After removal of the DMF under reduced pressure, the residue obtained is dissolved in methanol (5 mL) and filtered through a pad of silica gel (depth 2 cm) supported on a steel frit (diameter 3.5 cm). After washing the pad with methanol (ca. 1L) the crude product is eluted with acetic acid.inethanol: water (3:2:1, by vol.). Appropriate fractions are collected and, after evaporation of the solvent under reduced pressure, the residue obtained is purified by chromatography on a column (2.5 x 40 cm) of Sephadex LH-20 eluting with n-butanol:water:acetic acid (5:4:1, by vol., upper phase). After removal of the solvent from appropriate fractions under reduced pressure, the residue obtained is dissolved in methanol (5 mL) and the solution is passed through a short column (3.5 x 20 cm) of anion exchange resin (Amberlite IRA 400, chloride form). After collection of the eluate, solvent is removed under reduced pressure and the residue obtained is dried under high vacuum to yield the dichloride salt as violet crystals. 'H-NMR: 5H (300Mz, CD3OD): 0.75 (t, 3J7.5 Hz, 3 H), 1.05-1.20 (m, 14 H), 1.45-1.50 (m, 2 H), 2.05-2.15 (m, 4 H), 2.15-2.20 (m, 2 H), 2.95 (s, 18 H), 3.35-3.45 (in, 4 H), 3.95 (t, 3J7.5 Hz, 4 H), 4.55 (t, 3J7.5 Hz, 2 H), 6.85 (m, 1 H), 7.35 (m, 2 H), 8.85-8.90, 9.15-9.20, (3 xrn, 8 H), 10.10 (s, 2 H). COMPOUND 7 5,15-bis-[4-(3-Bromo-propyloxy)-phenyl]-porphyrin To a stirred solution of dipyrroleniethane (0.61 g, 4.1 mmol) and 4-(3-bromopropyloxy)-benzaldehyde (1.03 g, 4.2 mmol) in degassed dichloromethane (1 L), TFA (0.07 mL, 1.5 mmol) is added dropwise. The solution is stirred at room temperature in the dark under argon for 17 h. After addition of DDQ (2.76 g, 0.012 mol), the mixture is stirred at room temperature for a further hour. Filtration through silica gel (Fluka 60, 100 g) using dichloromethane for elution gives raw product which, after recrystallisation from dichloromethane :n-hexane, yields pure product as violet crystals. 'H-NMR: 5H (SOOMz, C6D6): -3.15 (2 H, s), 2.00 (quint, 3/7.5 Hz; 4 H), 3.30 (t, 3J 7.5 Hz, 4 H), 3,90 (t, V7.5 Hz, 4 H), 7.15-7.18, 7.95-8.15 (2 x m, 2x4 H); 9.15-9.20,(m, 8 H), 10.05 (s., 2H). COMPOUND 8 5,15-bis-(4- {3-[(3-Dimetliylainino-propyl)-dimethyl-aninionio]- propyloxy} -phenyi)-porphyrin dichloride Compound 7 (200 mg, 0.27 mmol) is dissolved in absolute DMF (40 mL) with NjNjN'jN'-tetramethyl-lp-propanediamine (5 mL, 13,9 mmol) and the solution is stirred at 50°C under argon overnight. After evaporation of the solvent under reduced pressure, the residue obtained is dissolved in methanol (5 mL) and the solution is filtered through a pad of silica gel (depth 2 cm) supported on a steel frit (diameter 3.5 cm). The pad is eluted with methanol (ca. 1L) followed by acetic acid:methanol:water (3:2:1, by vol.). After evaporation of the solvent from appropriate fractions, the raw product obtained is dissolved in methanol (5 mL) and further purified by chromatography on a column (2.5 x 40 cin) of Sephadex LH-20 using n-butanol:water:acetic acid (4:5:1, by vol., upper phase) as the developing phase. The first fraction eluted is the desired product. After removal of solvent under reduced pressure the residue obtained is dissolved in methanol (5 mL) and passed through a short column (3.5 x 20 cm) of am'on exchange resin (Amberlite IRA 400, chloride form). After removal of solvent under reduced pressure from the eluate, the residue is crystallised from diethylether and dried under high vacuum to give the product as violet crystals. !H-NMR: 5H (300MHz, CD3OD): 2.20-2.35 (m, 4 H), 2.40-2.50 (m, 4 H), 2.80 (s, 12 H), 3.05 (4 H, t, 3J7.8, 2 H), 3.25 (s, 12 H), 3.45-3.55 (bs, 4 H), 3.65-3.75 (m, 4 H), 4.30 (t, 3/4.2 Hz, 4 H), 7.40, 8,10 (2 x d, 3J 7.5 Hz, 2 x 4 H), 8.95, 9.45 (2x d, 3J 4.2 Hz, 8 H), 10.40 (s, 2 H). COMPOUND 9 5,15 -bis- [4-(3 -Triethylammonio-propyloxy) -phenyl] -porphyrin dichloride To a solution of Compound 7 (50 mg, 0.068 mmol) in absolute DMF (20 mL) is added triethylamine (4,7 mL} 0.034 mol, 500 eq.). The mixture is stirred at 60°C for 24 h. The solvent is removed under reduced pressure and the residue obtained is dissolved in methanol (5 mL) and filtered through a pad of silica gel (depth 2 cm) supported on a steel frit (diameter 3.5 cm). After washing with methanol (ca. 1L) the pad is eluted with acetic acid:methanol:water (3:2:1, by vol.). After evaporation of the solvent from the eluted fraction, the raw product obtained is dissolved in methanol (5 ml/) and purified by chromatography on a column (2.5 x 40 cm) of Sephadex LH-20 eluting with n-butanol:water:acetic acid (4:5:1, by vol., upper phase). The solvents are removed under reduced pressure from appropriate fractions, the residue obtained is dissolved in methanol (5 mL) and the solution is passed through a short column (3.5 x 20 cm) of anion exchange resin (Amberlite IRA 400, chloride form) to yield the product as a violet solid after evaporation of solvent. 'H-NMR: 8H (SOOMz, CD3OD): 1.25 (m, 18H), 2.13 (m, 4H), the signals for -CH2NCH2 (16H) are in the area 3.00-3.40 as a part of the inultiplet covered by the solvent signals, 4.15 (t, 4H, 3/= 7.5 Hz), 7.36 (d, 4H, 3J = 7.5 Hz), 8.15 (d, 4H, 3J = 7.5 Hz), 9.05 (d, 4H, 3J = 7.5 Hz), 9.54 (d, 4H, 3J =7.5 Hz), 10.45 (s,2H) COMPOUND 10 5,15-bis-[4-(3-Trrmethylarrmionio-propyloxy)-phenyl]-poiphyrin dichloride A solution of Compound 7 (300 mg, 0.41 lumol) in absolute DMF (50 mL) is transferred into a 100 mL autoclave. After addition of trimethylarnine (4.5 g ), the mixture is stirred at 50°C for 16 h. After evaporation of the solvent, the residue obtained is dissolved in methanol (5 mL) and the solution is filtered through a pad of silica gel (depth 2 cm) supported on a steel frit (diameter 3.5 cm). After washing with methanol (ca. 1L) the pad is eluted with acetic acid:methanol:water (3:2:1, by vol.). After evaporation of the solvent from appropriate fractions, the residue obtained is dissolved in methanol (5 mL) and purified by cnromatography on a column (2.5 x 40 cm) of Sephadex LH-20, eluting with n-butanol:water;acetic acid (4:5:1, by vol., upper phase). Two fractions are obtained, the first-eluting of which is the desired product. The solvent is removed under reduced pressure and the residue obtained is redissolved in methanol (5 mL) and the solution is passed through a short column (3.5 x 20 cm) of anion exchange resin (Amberlite IRA 400, chloride form). After evaporation of the solvent under reduced pressure, the residue is crystallised from methanol:diethylether and dried under high vacuum to give the product as violet crystals. 'H-NMR: 5H (300Mz, CD3OD): 2.40-2.60 (m, 4 H), 3.30-3.25 (bs, 18 H), 3.75-3.80 (m, 4 H), 4.40(t, 3/7.5 Hz, 4 H), 7.40, 8.20 (2 x d, 3J 8.5 Hz, 8 H), 9.05, 9.50 (2 x d, 3/4.5 Hz, 8 H), 10.45 (s, 2 H). COMPOUND 11 5,15~bis-[3-(3-Bromo-propyloxy)~phenyl]-poiphyrin To a stirred solution of dipyrrolemethane (1.22 g, 8.2 mmol) and 3-(3-bromo-propyloxy)- benzaldehyde (2.06 g, 8.2 mmol) in degassed dichloromethane (2 L), TFA (0.14 rnL, 3 mmol) is added dropwise. The solution is stirred at room temperature in the dark for 17 h under argon. After addition of DDQ (5.4 g, 0.024 mol), the mixture is stirred at room temperature for a further Hi. After removal of solvents under reduced pressure, the residue obtained is dissolved in dichloromethane (5 mL) and passed through a column (300 g) of silica (Fluka 60) using dichloromethane as eluent to give raw product which is crystallised from dicliloromethaue.-niethanol to yield pure material as violet crystals. 'H-NMR: 5H (SOOMz, CDC13): -3.20 (2 H, s), 2.40 (quint, 377.5 Hz, 4 H), 3.65 (t 3J 7.5 Hz, 4 H), 4.25 (t, 1/7.5 Hz, 4 H), 7.20-7.25, 7.60-7.65, 7,75-7.80 (3 x m, 8 H), 9.05, 9.25,(2 x d, 1/4.2 Hz, 8 H), 10.25 (s, 2 H). COMPOUND 12 5,15-bis- [3 -(3 -Tiimethylammonio-propyloxy)-phenyl] -porpliyrin dicliloride A solution of Compound 11 (400 mg, 0.543 rnmol) in DMF (50 rnL) is transferred into a 100 rnL autoclave. After addition of trimethylamine (6.3g), the mixture is stirred at 50°C for 8 h. After evaporation of the solvent under reduced pressure, the residue obtained is dissolved in niethanol (5 rnL) and the solution is filtered through a pad of silica gel (depth 2 cm) supported on a steel frit (diameter 3.5 cm). After washing the pad with methanol (ca.lL), elution with acetic acid:methanol:water (3:2:1, by vol.) affords fractions which, after evaporation of the solvent under reduced pressure, gives a solid residue. This is dissolved in methanol (5 rnL) and purified by chromatography on a column (2.5 x 40 cm) of Sephadex LH-20 eluting with n-butanol:water:acetic acid (4:5:1, by vol., upper phase). Two fractions are eluted from the column, the first of which is the desired product. After removal of the solvent under reduced pressure, the residue obtained is dissolved in niethanol (5 mL). The solution is passed through a short column (3.5 x 20 cm) of anion exchange resin (Amberlite IRA 400, chloride form), the solvent is removed under reduced pressure and the raw product is crystallised from methanol'.diethylether to give violet crystals which are dried under high vacuum. ]H-NMR: SH (300Mz, CD3OD): 2.30-2.35 (m, 4 H), 3.15 (s, 18 H), 3.95-4.05 (m, 4 H), 4.20-4.25 (m, 4 H), 7.40-7.45, 7.65-7.70, 7.80-7.85 (3 x m, 8 H), 9.00-9.05, 9.40-9.45,(2 x m, 8 H), 10.40 (m, 2 H). COMPOUND 13 5,15-bis-(4-Hydroxy-pheiiyl)-10,20-bis-(4-undecyloxy-phenyl)-porphyrin The third fraction eluted from the column during the chromatographic separation described for the synthesis of Compound 2 is characterised as 5,15-bis-(4-hydroxy-phenyl)-10,20-bis-(4-undecyloxy-phenyl)-porphyrin 'H-NMR: 5H (300MHz, CDC13): -2.88 (2 H, s), 0.85 (t, 3/7.5 Hz, 6 H), 1.20-1.40 (m, 28 H), 1.55 (br ni, 4 H), 1.80 (quint, 3J7.5 Hz, 4 H), 4.15 (t, 3J7.5 Hz, 4 H), 6.65, 7.15 (d, *J 8.1 Hz, 8 H), 7.80, 8.00 (d, 3/ 8,1 Hz, 8 H), 8.75-8.80 (m, 8 H). //-(my-Regioisomer geometry is assigned by ^H-^C^D-NMR in d-acetic acid. COMPOUND 14 5,10-bis-(4-Hydroxy-plienyl)-15,20-bis-(4-undecyloxy-pIienyl}-porphyriii The fourth fraction eluted from the column during the chromatographic separation described for the synthesis of Compound 2 is characterised as 5,10-bis-(4-hydroxyphenyl}-15,20-bis-(4-undecylox3'-phenyl)-poiphyrin ]H-NMR: 5H (300MHz, CDC13): -2.80 (2 H, s), 0.90 (t, 3/7.5 Hz, 6 H), 1.20-1.60 (m, 28 H), 1.65 (quint, 3/7.5 Hz, 4 H}, 2.00 (quint, 3J7.5 Hz, 4 H), 4.22 (t, 1/7.5 Hz; 4 H), 7.15 (d, 3J8,1 Hz, 4 H), 7.25 (d, 3J8.2 Hz, 4 H), 8.10 (d, 3J8.2 Hz, 4 H ), 8.15 (d, 3/8.2 Hz: 4 H), 8.80-8.90 (m, 8 H). cz's-Regioisomer geometry is assigned by 1H-I3C-2D-1S!MR in d-acetic acid. COMPOUND 15 5,10,15-tris-[4-(3-Bromo-propyloxy)-phenyl]-20-(4-undecyloxy-phenyl)-' porphyrin Under an argon atmosphere, Compound 2 (200 ing, 0.24 inmol) is dissolved in absolute DMF (40 mL) in the presence of K2C03 (500 mg) and 1,3-dibromopropane (1.02 mL, 10 mmol). The mixture is heated overnight at 80°C. Work-up is as the procedure given for Compound 2 described above. The product is purified by column chromatography on silica gel (Merck 60) eluting with hexane: ethyl acetate (5:1, by vol.). 8H (300MHz, CDC13): -2.75 (2 H, s), 0.85 (t, 3J7.5 Hz, 3 H), 1.20-1.45 (ni, 14 H), 1.50 (quint, 3J1.5 Hz, 2 H), 1.90 (quint, 3/7.5 Hz, 2 H), 2.40 (quint, 3/7.4 Hz, 6 H), 3.65 (t, 3J7.4 Hz, 6 H), 4.16 (t, 3J 1.5 Hz, 2 H), 4.25 (t, 3/7.5 Hz3 6 H), 7.18-7.20 (m, 8 H), 8.00-8.05 (m, 8 H), 8.75-8.85 (m, 8 H). COMPOUND 16 5,10.15-tiis-[4-(3-Trieth3/lammonio-prop\iox37)-phenyl]-20-(4- undecyloxy-phenyl)-poiphyrin tri chloride Compound 15 (200 mg, 0.17 nimol) is dissolved in absolute DMF (40 mL) with triethylarnine (5 mL, 34.5 rnmol, 208 eq.). The mixture is., heated to 50°C for 48 h. After removal of DMF under vacuum, the residue obtained is dissolved in methanol and purified by column chromatography using silica gel (Merck, 60) eluring with methanol:water:acetic acid (2:1:3, by vol.) and then acetic acid:pyridine (1:1, by vol.). Removal of solvent from appropriate fractions under vacuum affords raw product which is dissolved in methanol:aqueous NaCl (1M) (5 mL. 1:1, by vol.). The mixture is stirred for 30 mins and filtered through a pad of silica gel (depth 2 cm) supported on a steel frit (diameter 3.5 cm). After washing the pad with methanol (200 mL) it is eluted with methanol:water:acetic acid (2:1:3, by vol.). After evaporation of solvent from appropriate combined fractions, the residue obtained is dissolved in methanol (2mL) and dichloromethane (5 mL) is added dropwise. The precipitated white gel is collected by filtration and the solvent is removed under high vacuum. H-NMR: 5H (300MHz, CD3OD): 0.90 (t, 3/7.5 Hz, 3 H), 1.20-1.45 (m, 43H), 1.45-1.65 (bs, 2 H), 2.25-2.40 (bs, 6 H), 3.35-3.45 (bs, 24 H), 3.50-3.60 (bs,, 6 H), 4.25 (t: 3/7.5 Hz, 2 H), 4.40-4.45 (bs, 6 H), 7.25-7.40, 8.10-8.20 (m, 5 16 H), 8.80-9.10 (bs, 8 H). COMPOUND 17 5-[4-(3-Hydroxy-phenyl)]-15-(3-undecyloxy-phenyl)-porphyrin 105-15-bis-(3-Hydroxy-phenyl)-porphyrin (Wielie, A., Simonenko, E. J., Senge, M. O. and Roeder, B. Journal ofPorphyrins and Phthalocyanines 5, 758-761 (2001)) (86 mg, 0.17 mmol) is dissolved and K2C03 (250 mg, 15 7.1 mmol) is suspended in DMF (40 mL). To the vigorously-stirred mixture a solution of 1-bromoundecane (0.04 mL, 0.17 mmol) in DMF (5 mL) is added dropwise at 50 °C during 30 mins and the mixture is heated at that temperature for 1 h. After removal by filtration of K2CO3, DMF is removed under high vacuum. The residue obtained is purified by column 20 chromatography using silica gel (Merck 60) eluting with n-hexane:ethyl acetate (10:1, by vol.). The 2nd fraction is collected and dried under high vacuum to give the product. ]H-NMR: 6H (300Mz, CDC13): -3.15 (2 H, s), 0.75 (t V7.5 Hz, 3 H), 1.10-1.30 (m, 14 H), 1.35 (m, 2 H), 1.80 (quint, V7.5 Hz, 2 H), 4.05 (t, V7.5 Hz, 2 H), 6.85-6.90, 7.20-7.25, 7.35-7.45, 7.50-7.65, 7.75-7.80 (5 x m, 8 H), 8.855 8.95, 9.10, 9.20 (4 x d, 3J4.9 Hz, 4 x 2 H), 10.15 (s, 2 H). COMPOUND 18 5,10,15-tiis-(3-Hydroxy-phenyl)-20-(3-dodecyloxy-phenyl)-porphyrin 3-Hydroxybenzaldehyde (1.8 g, 14.8 mmol, 3 eqv.) and 3-dodecyloxybenzaldehyde (1.35 g, 4.9 mmol, 1 eqv.) are dissolved in a mixture of acetic acid (145 mL) and nitrobenzene (98 mL, 960 mmol) and heated to 120°C. Pyrrole (1.35 mL, 19.6 mmol, 4 eqv.) is added in one portion and the mixture is stirred at 120°C for Ih. After cooling to room temperature, solvents are removed in vacuo at 50°C. The product is isolated by chromatography on a column (500 g) of silica using toluene as eluent. The desired product is obtained as the fifth fraction from the column and is re-chromatographed using a smaller (200 g) silica coulmn eluted with toluene. The product is obtained as a violet solid after evaporation of the solvent. :H-NMR: 6H (300 MHz, CDC13): 0.64 (t, 3 H, 1/6.8 Hz), 0.94-1.15 (m, 16 H), 1.25 (bs, 2 H), 1.62 (bs, 2 H), 3.90 (bs, 2 H), 6.33-6.95 (m, 8 H), 7.08-7.60 (m, 8 H), 8.20-8.47 (m, 4 H), 8.51-8.70 (m, 4 H) COMPOUND 19 5- {3-[bis-(2-Diethylamino-ethyl)-aminopropyloxy]-phenyl} -15-(3- undecyloxy-phenyi)-porphyrin Compound 17 (50 mg, 0.065 mmol) is dissolved with N,N,N\NA-tetraethyldiethylenetriamine (ImL, 39 mmol) in THF(10 mL) and the mixture is stirred at room temperature for 4 days. After evaporation of the solvent the residue is dissolved in diethyl ether (20mL) and the solution is washed with water (5 x 30 mL). The organic phase is dried (Na2S04) and concentrated under high vacuum. The mixture is purified by column chromatography (silica gel, Merck 60) eluting with n-hexane:ethyl acetate (5:1, by vol.) followed by n-hexane: ethyl acetate:triethyl amine (10:10:1, by vol.). After collection of appropriate fractions and removal of solvent under reduced pressure, pure product is obtained by crystallisation of the residue from diethyl ether :methanol. !H-NMR: 6H (300Mz, CDC13): 0.80 (t, 3J7.5 Hz, 3 H), 0.9 (t, 3J 7.5 Hz, 12 H), 1.20-1.40 (m, 14 H), 1.45 (quint, 3J7.5 Hz, 2 H),1.80 (quint, V 7.5 Hz, 2 H), 1.95 (quint, 3J7.5 Hz, 2 H),2.40-2.60 (m, 16 H), 2.65 (t,3/7.5 Hz, 2 H), 4.10 (t, 3/7.5 Hz, 2 H), 4.20 (t, 1/7.5 Hz, 2 H), 7.30-7.40, 7.55-7.65, 7.75-7.80 (3 x m, 8 H), 9.10-9.15, 9.20-9.25 (2 x m, 2 x 4 H), 10.15 (s, 2 H). COMPOUND 20 5-[4-(3-Bromo-propylox)0-plienyl]-15-(4-dodecyloxy-phen}'l)-porpli}Tin To a stirred solution of dipyrrolemetliane (0.31 g, 2.1 minol), 4-(3-bromo-proyloxy)-benzaldeliyde (0.27 g, 1.1 imnol) and 4-dodecyloxy-benzaldehyde (0.32 g, 1.1 mrnol) in degassed dichloromethane (500 niL). TFA (0.035 mL, 1.5 mmol) is added dropwise. The solution is stirred at room temperature in the dark for 17 h under argon. After addition of DDQ (1.38 g, 6 mmol), the mixture is stirred at room temperature for a. further hour. Purification b}' column chromatography using silica gel (Merck 60, 400 g) with toluene as eluent affords the product (2nd fraction) together with Compound 7 (3Td fraction). !H-NMR: 5H (SOOMz, CDC13): -3.15 (2 H, s), 0.90 (t, 3J7.5 Hz, 3 H), 1.20-1.40 (m, 16 H), 1.55 (quint, 3J 7.5 Hz, 2 H), 1.90 (quint, V 7.5 Hz, 2 H), 2.40 (quint, 3J 7.5Hz, 2H), 3.75 (t, 3J 7.5 Hz, 2 H), 4.20 (t, 3J 7.5 Hz, 2 H), 4.35 (t, 1/7.5 Hz, 2 H), 7.20-7.30, 8.10-8.15 (2 x m, 8 H), 9.10-9.15, 9.25-9.30 (2 x m, 2 x 4 H), 10.20 (s, 2 H). COMPOUND 21 5,10,15,20-teti-akis-(3-Hydroxy-phenyl)-porphyrin 3-Hydroxybenzaldehyde (0.910 g, 7.45 mmol) is dissolved in propionic acid (50 mL) and heated to 140°C. Pyrrole (0.52 mL, 7.45 mmol) is added in one portion and the mixture heated at reflux for 2h. Stirring is continued for an additional 12 h at room temperature. Propionic acid is removed in vacua and the residue dissolved in acetone and purified by chromatography 011 a column (250 g) of silica which is eluted with toluene containing a continuously increasing proportion of ethyl acetate. The product is eluted with toluene:ethyl acetate (6:1 by vol.). Solvent is removed hi vacuo to afford the product as a violet solid. !H-NMR: 5H (300 MHz, d6-acetone): 7.18 (d, 4H, 3J= 8.25 Hz), 7.49 (t, 4H, 3J= 8.25 Hz), 7.56-7.62 (m, 8H), 8.81 (m, 8 H) COMPOUND 22 5,10,15-tris-[4-(3-Bromo-propyloxy)-phenyl]-20-(4-dodecyloxy-phenyl)- porphyrin To a stirred solution of pyrrole (0,7 ml, 10 namol), 4-(3-bromoproyloxy)-benzaldehyde (1.8 g, 7.5 mmol) and 4-(n-dodecyloxy)-benzaldehyde (0.725 g, 2.5 mmol) in degassed dichloromethane (1 L) is added TFA (0.085 ml, 10 mmol) dropwise. The reaction solution is stirred under argon at room temperature in the dark for 17 h. After addition of DDQ (6.9 g, 30 mmol), the reaction mixture is stirred at room temperature for a further Hi. The solvents are removed under reduced pressure and the residue re-dissolved in toluene. Chromatographic purification on a column (3.5 x 30 cm J of silica gel (Merck 60) using toluene:n-hexane (1:4 by vol.) as eluent gives crude product which is purified by recrystallisation from methanol:dichloromethane, giving violet crystals. ]H-NMR: 8H (300MHz, CDC1,): 0.90 (t, 3J7.5 Hz, 3 H), 1.20-1.45 (m, 16 H), 1.60 (quint, 3J7.5 Hz, 2 H), 1.90 (quint, 3J7.5 Hz, 2 H), 2.50 (quint, V7.4 Rz, 6 H), 3.75 (t, 3/7.4 Hz, 6 H), 4.20 (t, V7.5 Hz, 2 H), 4.35 (t, 3J7.5 Hz, 6 H), 7.25-7.30 (m, 8 H), 8.15-8.30 (m, 8 H), 8.80-8.85 (m, 8 H). COMPOUND 23 5-{4-[3-Diniethyl-(3-dimethylaminopropyl)-ammonio-propyloxy]phenyl}-15-(4-dodec3doxy-phenyl)-porphyrin chloride Compound 20 (30 mg, 0.038 mmol) is dissolved with N,N,N',N'~ tetramethyl-1,3-propanediamine (156 mg, 1.2 mmol) in THF:DMF(1:1 by vol., 20 mL) and stirred at 50 °C for 18 h. After evaporation of the solvent under reduced pressure, the residue is dissolved in dichloromethane and purified by column chromatography (silica gel Merck 60) eluting with acetic acid:methanol:water (3:2:1, by vol.). After combining appropriate fractions and removal of solvent under reduced pressure, the residue is crystallised from dichloromethanerhexane to afford the product as violet crystals. 'H-NMR: 5H (300Mz, CDC13+1 % acetic acid): 0.85 (m, 3 H), 1.20-1.40 (m, 18 H), 1.55-1.60 (m, 2 H), 1,60-1.65 (m, 4H), 2.10-2.20 (bs, 8 H), 3.15-3.25 (m, 8 H), 3.75 (bs, 2 H), 4.20 (bs, 2 H), 4.35 (bs, 2 H), 7.15-7.20, S. 10-8.15 (2 x m, 8 H), 8.95-9.00, 9.10-9.15, 9.25-9.30 (3 x bs, 8 H), 10.20 (s, 2H). COMPOUND 24 5,15-bis-(3 -Methoxy-plienyl)-10-undecyl-poiphyrin Into a 50 mL flask containing lithium (500 mg, 71 mmol) is added freshly distilled di ethyl ether (15 mL) under an argon atmosphere. The suspension is refluxed for 1 hour, cooled to 15 °C and treated with a solution of n-undecylbromide (6.58 g, 71 mmol) in ether (6 mL) added dropwise via syringe. The mixture is cooled to 7-10 °C and, after 5 min, when the suspension becomes slightly cloudy and bright spots appear on the lithium metal, the remainder of the n-undecylbromide solution is added at an even rate over a period of 30 min while the internal temperature is maintained at below 10 °C. Upon completion of addition, the mixture is stirred further for 1 h at 10 °C. The suspension is filtered under argon to remove excess lithium and lithium bromide. 5,15-bis-(3-Memoxy-phenyl)-porphyrm (100 mg, 0.19 mmol) is dissolved in anhydrous THF (30 mL) at -50 °C under an argon atmosphere. The organolithium reagent described above (5 mL) is added dropwise to the mixture. After 5 min the cooling bath is removed and the mixture is warmed to room temperature, After stirring at room temperature for 15 min the reaction is quenched by slow addition of water (2 mL). After 15 min the mixture is oxidized "by the addition of DDQ (4 mL, 0.4 mmol, 0.1 M in THF) and stirred for a further 15 min. The mixture is filtered through alumna (neutral, Brockman grade +) and purified by column chromatography on silica gel eluting with hexane:dichloromethane (4:1 by vol.). The first fraction is collected and crystallised from methanol:dichloromethane. 'H-NMR: SH (SOOMz, CDC13): -3.05 (bs, 2 H, s), 0.80 (t, 3J7.5 Hz, 3 H), 1.10-1.20 (m, 12 H), 1.25 (in, 2 H), 1.70 (quint, 3J7.5 Hz, 2 H), 2.40 (quint, 3J7.5 Hz, 2 H), 3.85 (s, 6H), 4.95 (t, 3J7.5 Hz, 2 H), 7.20-7.23, 7.50-7.60, 7.65- 7.75 (3x m, 8 H), 8.85-8.90, 9.10-9.15, 9.35-9.40 (3 x m, S H), 9.95 (s, 1H). COMPOUND 25 3-[( {3-[(3- {4-[ 15-(4-Dodecyloxy-phen)d)-porphyrin-5-yl]-phenoxy} -propyl)-diniemyl~anxmonio] -propyl} -dimethyl-ammonio)-propyl] -trimethyl-ammonium trichloride Compound 23 (20 mg, 0.022 mmol) and (l-bromopropyl)-trimetliyl-ammonium bromide (26 ing, 0.1 mmol) are dissolved in DMF(15 ml) and stirred overnight at 50°C. After evaporation of the solvent under reduced pressure, the residue is dissolved in methanol (5 ml) and applied to a pad (3 cm deep) of silica gel which is washed with methanol (500 ml) followed by acetic acid:methanol:water (3:2:1 by vol.). After evaporation of the solvent the residue is purified by column chromatograpliy (silica gel Merck 60) using at first acetic acid:methanol:water (3:2:1 by vol.) and then pyridine: acetic acid (1:1 by vol.). The second fraction eluted is collected and dried under vacuum. The residue is dissolved in methanol (2 ml) and purified by chromatography on a column (2.5 x 40 cm) of Sephadex LH-20 which is eluted with n-butanol:acetic acid:water (5:1:4 by vol., upper phase). After removal of solvent under reduced pressure, the residue is dried under vacuum at 80 °C. NMR spectroscopy indicates the product is contaminated with a small proportion of elimination products. COMPOUND 26 5,10,15-tris-[4-(3-Diethylamino-propyloxy)-phenyl]-20-(4-dodecyloxy- phenyl)-porphyiin Compound 22 (50 ing, 0.06 nrmol) and freshly distilled diethylaniine (5 ml) are dissolved in absolute DMF (30 ml) under argon. The reaction mixture is stirred at room temperature for 20 h and poured into ethyl acetate (50 ml). The mixture is washed with water (4 x 50 ml) and, after drying the combined organic phases (Na2SO4), evaporation of solvent affords a residue which is purified by chromatography on a column (2.5 x 30 cm) of silica (Merck 60) which is eluted with ethyl acetate :n-hexane:triethyl amine (10: 10: 1, by vol.). Fractions are combined as appropriate, the solvent evaporated under reduced pressure and the residue dried under high vacuum. Reciystallisation from dicliloroinetlianem-hexane affords pure product. 'H-NMR: oH (300MHz, CDC13): 0.85 (t, V7.5 Hz, 3 H), 1.05 (m, 18 H), 1.20-1.45 (m, 18 H), 1.55 (quint, 3J7.5 Hz, 2 H), 2.15 (quint, 3J7.5 Hz, 6 H), 2.75 (quint, , 3J 7.4 Hz, 6 H), 3.15-3.25 (in, 12 H), 4.15 (t, 3J 7.5 Hz, 2 H), 4.25 (t, 3J7.5 Hz, 6 H), 7.15-7.20 (m, 8 H), 8.00-8.05 (m, 8 H), 7.95-8.05 (m,8H). COMPOUND 27 5,15-bis-(3-Hydroxy-phenyI)-10-undecyl-porphyrin To a solution of Compound 24 (95 mg, 0.14 mmol) in anhydrous dicllloromethane (SO mL) under an argon atmosphere BBr3, (6 mL, IM in dichlorornethane) is added dropwise at -70 °C and the mixture is stirred for 1 h. The mixture is warmed to room temperature and stirred overnight then cooled to -10°C and hydrolysed by addition of 2 mL water during 1 h. NaHCO3 (3 g) is added directly to neutralisation. The mixture is stirred for a further 12 h. After removal of NaHC03 by filtration and of dichoronaethane under vacuum, the residue obtained is purified by column chroniatography using silica gel eluting with dichloroniethane. After removal of solvent from appropriate combined fractions and drying under high vacuum the product is obtained as violet crystals. !H-NMR: 5H (SOOMz, CDC13): -3.05 (bs; 2 H, s), 0.85 (t, V7.5 Hz, 3 H), 1.20-1.40 (m, 12 H)5 1.50 (m, 2 H), 1.80 (quint, 3J7.5 Hz, 2 H), 2.55 (quint, V7.5 Hz, 2 H), 5.00 (t, 3/7.5 Hz, 2 H), 7.15-7.25, 7.50-7.60, 7.80-7.90 (3x m; 8 H), 8.95-9.00, 9.20-9.25, 9.50-9.60 (3 x m, 8 H), 10.15 (s, 1H). COMPOUND 28 5,15-bis-[3-(3-Trimethylammmonio--propyloxy)-plienyl]-10-iindecyl-porpliyrin dichloride To a solution of Compound 27 (50 mg, 0.08 mmol) in DMF (20 mL) under an argon atmosphere K2C03 (100 mg, 0.72 mmol) and (3-bromopropyl)-trimethylammonium bromide (300 mg, 1.2 mmol) are added and the mixture is stirred at 50°C for 18 h. After removal of solvent under high vacuum the residue obtained is dissolved in methanol (5 mL) and filtered through a pad of silica gel (depth 2 cm) supported on a steel frit (diameter 3.5 cm). After washing the pad with methanol (500 mL) it is eluted with acetic acid:methanol:water (3:2:1, v:v). After drying of appropriate combined fractions under high vacuum the residue is dissolved in methanol and purified by column chromatography on Sephadex LH-20 eluting with n-butanol:acetic acid:water (5:1:4, by vol., upper phase). After evaporation of solvent the residue obtained from the first fc.odon eluted is dissolved in methanol and passed through a short column of anion exchange resin (Amberlite IRA 400, chloride form) to give, after evaporation of solvent, the pure product. 'H-NMR: 5H (300Mz, CD3OD): 0.85 (t, 3/7.5 Hz, 3 H), 1.20-1.40 (m, 12 H), 1.50 (m, 2 H), 1.80 (m, 2 H), 2.40 (bs, 4 H), 2.55 (m, 2 H), 3.20 (bs, 18 H), 3.65 (bs, 4 H), 4.35 (bs, 4 H), 5.10 (m, 2 H), 7.50-7.55, 7.70-7.85 (2 x m, 8 H), 8.95-9.00,9.25-9.24, 9.50-9.70 (3 x bs, 8 H), 10.15 (bs, 1H). COMPOUND 29 5,10-bis-[4-(3-Trimeihylammonio-propyloxy)-phenyl]-15,20-bis-(4- undecyloxy-phenyl)-porphyrin dichloride Compound 14 (50 mg, 0.05 irrmol) is dissolved and K2CO3 (150 mg, 1.1 mmol) is suspended in DMF (30 mL). To the vigorously-stirred mixture a solution of (l-bromopropyl)-trimethylaminonium bromide (0.3 g, 16.6 mmol) in DMF (10 mL) is added dropwise at 50°C and the mixture is heated for 18 h. After removal of DMF under high vacuum, the residue obtained is dissolved in methanol (5 mL) and filtered through a pad of silica gel (depth 2 cm) supported on a steel frit (diameter 3.5 cm). After, washing the pad with methanol (ca. 500 mL) it is eluted with acetic acid:methanol:water (3:2:1, by vol.). After evaporation of solvent from appropriate combined fractions the residue obtained is purified by chromatography on a column (2.5 x 40 cm) of Sephadex LFf-20 eluting with n-butanol:water:acetic acid (5:4:1, by vol., upper phase) for further separation from the excess ammonium salt and other by-products. After removal of solvent under reduced pressure the residue obtained is dissolved in methanol and passed through a short column (3.5 x 20 cm) of anion exchange resin (Amberlite IRA 400, chloride form). After evaporation of solvent under reduced pressure, the product is dried under high vacuum. !H-NMR: 5H (300MHz, CD3OD): 0.80 (t, V 7.5 Hz, 6 H), 1.15-1.35 (m, 28 H), 1.35-1.45 (bs, 4 H), 1.70-1.80 (bs, 4 H), 2.30-2.40 (bs, 4 H), 3.15-3.30 (bs, 18 H), 3.65-3.75 (bs, 4 H), 4.00-4.05 (m, 4 H), 4.30-4.40 (bs, 4 H), 7.00-7.15, 7.20-7.30, 7.80-95, 7.95-8.15 (4 xm, 4 x 4 H), 8.60-9.00 (bs, 8 H). COMPOUND 30 5,10,15-tris-(3-Hydroxy-phenyl)-20-(3-undecyloxy-phenyl)-poiphyi-in Pyrrole (1.31 g, 19.6 mmol) is added in one portion to a mixture of 3-hydroxybenzaldehyde (1.8 g, 14.8 mmol) and 3-undecyloxybenzaldehyde (1.36 g, 4.9 mmol) in acetic acid (145 mL) and nitrobenzene (118 g, 960 mmol) preheated to 130°C and the mixture is stirred for 1 hour at 120°C. The mixture is cooled and solvent removed under high vacuum. The residue is dissolved in dichloromethane (5 mL) and purified by column chromatograpliy using silica gel (Merck 60) ehrting with hexane:toluene (4:1, by vol.). The product is obtained after removal of solvent from the eluate under reduced pressure and drying the obtained residue under vacuum. 'H-NMR: 5H (300Mz, CDC13): 0.75-0.80 (m, 3 H), 1.05-1.35 (m, 14 H), 1.40-1.50 (m, 2 H), 1.75-1.85 (m, 2 H), 3.90-4.10 (m,2 H), 6.90- 7.70 (m, 16 H), 8.45-8.80 (m, 8 H). COMPOUND 31 5-{4-[3-Dimethyl-(3-1iiinethylamnionio-propyl)-animomo-propyloxy]-phenyl} -15-(4-dodec.yloxy-phenyl)-porphyriii dichloride Compound 23 (50 mg, 0.055 mrnol) is dissolved with methyl iodide (5 mL, 80 mmol) in absolute DMF(30 mL) and the mixture is stirred at 40°C for 3h. After evaporation of solvent the residue obtained is dissolved in methanol (5 mL) and filtered through a pad of silica gel (depth 2 cm) supported on a steel frit (diameter 3.5 cm). After washing the pad with methanol (ca. 1 L) it is eluted with dicliloromethanermethanol (2:3 by vol., 500 mL) and then acetic acid:water:methanol (3:1:2, by vol.). After removal of solvent from appropriate pooled fractions the residue obtained is dissolved in acetic acid and purified by column chromatography on Sephadex LH-20 eluting with acetic acid. After evaporation of solvent from appropriate pooled fractions and drying the residue obtained under high vacuum, the residue is dissolved in methanol and passed through a small column (3.5 x 20 cm) of anion exchange resin (Arnberlite IRA 400, chloride form). After evaporation of solvent from the eluate, the product is dried under high vacuum. COMPOUND 32 5-[4-(3-Dimemyldecyl-aiimioniopropyloxy)-phenyl]-15-{4-[3-drmet]iyl-(3-dimethylammopropyl)-anmioniopropyloxy]-phenyl}-porphyrin dichloride Me2N Compound 23 (50 mg, 0.068 mmol) is dissolved with N,N,N',N'-tetramethyl-l,3-propanediarnuie (354 mg, 1.36 mmol) and N,N-dimethyldecylamine (1 g, 2.72 mmol) in DMF:THF(30 mL, 1:1, by vol.) and the mixture is stirred at 50°C overnight. After evaporation of the solvent under reduced pressure the residue obtained is dissolved in methanol (10 mL) and filtered through a pad of silica gel (depth 2 cm) supported on a steel frit (diameter 3.5 cm). After washing the pad with methanol (ca. 500 mL) it is eluted with acetic acid:methanol:water (3:2:1, by vol.). The first two fractions eluted are combined and after evaporation of the solvent under reduced pressure the residue obtained is dissolved in methanol and purified by chromatography on a column (2.5 x 40 cm) of Sephadex LH-20 eluting with n-butanol:water:acetic acid (4:5:1, by vol.). After removal of solvent under reduced pressure from the second fraction eluted, the residue is dissolved in methanol (5 mL) and passed through a short column (3.5 x 20 cm) of anion exchange resin (Amberlite IRA 400, chloride form). The eluate is evaporated to dryness and the residue obtained is dried under high vacuum to afford the product. 'H-NMR: 6H (300MHz, CD3OD): O.SO (m, 3 H), 1.05-1.25 (m, 10 H), 1.25-1.40 (bs, 2 H), 1.80-1.90 (bs, 4 H), 2.15-2.30 (bs, 2 H), 2.80-3.60 (m, 20 H), 3.80-3.95 (bs, 4 H), 7.05-7.15, 7.85-8.00 (2 x m, 2 x 4 H), 8.75-8.90, 9.20-9.35 (2xbs,2x4H), 10.15(bs,2H). COMPOUND 33 5,10,15-Ms[3-(3-Triniethyl-aiimionioprop)4ox};r)-phenyl]-20-(3-undecyloxy-phenyl)-porphyrin trichloride Compound 30 (100 mg, 0.12 nrmol) is dissolved and K2CO3 (230 mg, 1.7 mmol) is suspended in DMF (30 mL). To the vigorously-stirred mixture a solution of (l-bromopropyl)-trimethylamnionium bromide (0.3 g, 16.6 mmol) in DMF (10 mL) is added dropwise at 50°C during 30 mins and the mixture is heated for 18 h. After removal of DMF under reduced pressure, the residue obtained is dissolved in methanol (5 mL) and filtered through a pad of silica gel (depth 2 cm) supported on a steel frit (diameter 3.5 cm). After washing the pad with methanol (ca. 500 mL) it is eluted with acetic acid:methanol:water (3:2:1, by vol.). After evaporation of solvent from appropriate combined fractions under reduced pressure, the residue is purified by chromatography on a column (2.5 x 40 cm) of Sephadex LH-20 eluting with n-butanol:water:acetic acid (5:4:1, by vol.,, upper phase). After removal of solvent under reduced pressure from the eluate, the residue obtained is dissolved in methanol and the solution is passed through a short column (3.5 x 20 cm) of anion exchange resin (Amberlite IRA 400, chloride form). Evaporation of solvent from the eluate gives the product which is dried under high vacuum. 'H-NMR: 5H (300MHz, CD3OD): 0.75-0.80 (m, 3 H), 1.00-1.40 (m, IS H), 1.60-1.80 (bs, 2 H), 2.25-2.40 (bs, 6 H), 3.29 (bs, 27 H), 3.40-3.60 (m, 6 H), 3.90-4.00 (m, 2 H), 4.05-4.25 (m, 6 H), 7.10-7.20, 7.25-7.40, 7.60-7.80, 7.80-7.90 (4 x m, 16H), 8.70-9.00 (bs, 8 H). COMPOUND 34 5,15-bis-(3-Hydroxy-phenyl)-porphyrin This is prepared as described by Wielie, A., Simonenko, E. J., Senge, M. O. and Roeder, B. Journal ofPorphyrins and Phthalocyanines 5, 758-761 (2001). COMPOUND 35 5,10J5-tris-(4-Hydrox}'-phenyl)-20-(4-tetradecyloxy-phenyl)-poipliyriii 5,10,15,20-tetralusporphyrm (170 mg, 0.25 irrmol) is dissolved and K2C03 (0.65 g, mmol) is suspended in DMF (30 mL). To the vigorously stirred reaction mixture a solution of 1-bromotetradecane (0.1 mL, 0.45 mmol) in DMF (10 mL) is added dropwise at 50°C during 30 mins and the mixture is heated for 1.5h. After evaporation of solvent, the residue is dissolved in toluenerethanol (1:1 by vol., ca. 5 mL) and purified by chrornatography using a column (5 x 25 cm) of silica gel (Merck 60) which is washed with toluene. After the elution of the first 3 fractions, ehition is continued using toluene:ethyl acetate (2:1 by vol.). The fifth compound elutedis collected, the solvent evaporated and the residue dried under high vacuum to afford product as violet crystals. JH-NMR: 5H (300MHz, d6-acetone): 0.85 (t, 3J7.5 Hz, 3 H), 1.15-1.55 (m, 20 H), 1.45 (quint, 3J 7.5 Hz, 2 H), 1.75 (quint, 3J 7.5 Hz, 2 H), 4.10 (t, 3J 7.5 Hz; 2 H), 7.20 (d, 3J 8.5 Hz, 2 H), 7.25 (d, 3J 8.5 Hz, 6 H), 8.00-8.15 (m, 8H), 8.80-9.10 (m, 8 H). COMPOUND^ 5,10,15-tiis-[4-(3-Trimethyl-animomopropyloxy)-plienyl]-20-(4-tetradecyloxy-phenyl)-porphyrin trichloride The n-tetradecyloxy-analogue of Compound 2, prepared similarly as described above for Compound 2 but using 1-bromotetradecane in place of 1-bromoundecane, (50 mg, 0.057 mrnol) and (1-bromopropyl)-trimeihylammonium bromide (210 mg, 0.8 inmol) are dissolved and K2C03 (230 mg, 1.7 rnmol) is suspended in DMF (20 mL). The vigorously stirred mixture is stirred at this temperature for 18 h. After removal of DMF under reduced pressure the residue obtained is dissolved in methanol (5 mL) and filtered through a pad of silica gel (depth 2 cm) supported on a steel frit (diameter 3.5 crn). After washing the pad with methanol (ca. 500 mL) it is eluted with acetic acid:methanol: water (3:2:1, by vol.). After evaporation of the solvent from appropriately combined fractions, the residue obtained is purified by chi'omatography on a column (2.5 x 40 cm) of Sephadex LH-20 eluting with n-butanol:water:acetic acid (4:5:1, by vol., upper phase) for separation from the excess of ammonium salt and other contaminating materials. After elution and removal of the solvent from appropriate fractions, the residue obtained is dissolved in methanol (5 mL) and passed through a short column (3.5 x 20 cm) of anion exchange resin (Amberlite IRA 4003 chloride form). Solvent is removed under reduced pressure and the residue obtained is dried under high vacuum to afford the product as violet crystals. !H-NMR: 5H (300MHz, CD3OD): 0.75 (t, 3J 7.5 Hz, 3 H), 0.95-1.25 (m, 22 H), 1.50-1.65 (bs, 2 H), 2.20-2.40 (bs, 6 H), 3.05-3.15 (bs, 27 H), 3.45-3.60 (bs, 6 H), 3.60-3.80 (bs, 2 H), 4.05-4.25 (bs, 6 H), 6.80-7.25, 7.65-8.05, (2 x m, 16 H), 8.45-8.95 (bs, 8 H). COMPOUND 37 5-(4-{3-[2,4,6-tris-(Dimethylaminomethyl)-phenyloxy]-propyloxy}- phenyl)-15-(4-dodecyloxy-phenyI)-porphyrin Compound 20 (50 mg, 0.063 rnmol) is dissolved in DMF (20 mL) in the presence of 2,4,6-tris-(dimethylaminomethyl)-phenol (1 mL, 3.7 mmol) and stirred at 50°C overnight. After evaporation of the solvent, the residue is crystallised from dichloromethane:methanol to remove the excess of aroine. After filtration, the porphyrins are re-dissolved in dichloromethane and purified by chromatography on a column of silica gel (Merck 60) which is washed with dichloromethane. Evaporation of solvent under reduced pressure and recrystallisation of the residue from iicliloromethane:methanol gives the product as violet crystals. 'H-NMR: 6H (SOOMz, CDC13): -3.15 (2 H, s), 0.85 (t, 3J4.5 Hz, 3 H), 1.20-1.40 (m, 18 H), 1.55 (quint, 3/4.5 Hz, 2 H), 1.90 (quint, 3/4.5 Hz, 2 H), 2.20 (s, 18 H), 2.55 (t, 1/5.2 Hz, 2 H), 3.45 (s, 6 H), 4.15 (t, 3J5.5 Hz, 2H), 4.20 (t, 3J 5.5 Hz, 2 H), 4.35 (t, V 7.5 Hz, 2 H), 6.85 (2 x s, 2 H), 7.20-7.30, 8.10-8.15 (2 x m, 8 H), 9.00-9.05, 9.25-9.30 (2 x m, 2x4 H), 10.20 (s, 2H). COMPOUND 38 5310,15-tris-(4-Hydroxy-phenyl)-20-(4-decyloxy-phenyl)-porpliyrin (Figure Remove)*((5,10,15,20-tetalds-(4-Hydroxy-phenyl)-porphyrin (100 ing, 0.15 mmol) is dissolved and K2C03 (230 nig) is suspended in DMF (30 niL). To the vigorously stirred reaction mixture a solution of 1-bromodecane (0.016 mL, 0.11 mmol) in DMF (10 inL) is added dropwise at 70°C during 30 mins and the mixture is stirred for 1.5L After evaporation of solvent, the residue is dissolved in toluene:etlmnol (1:1 by vol.,, ca. 3 niL) and purified by chromatography on a column (150 g) of silica gel (Merck 60) using toluene as eluent. After elution of the first 3 fractions, the column is eluted with toluene:ethyl acetate (2:1 by vol.) and the 5th fraction eluted is collected, the solvent removed and the residue dried under high vacuum to give the product as violet crystals. !H-NMR: 8H (SOOMz, d6-acetone): 0.95 (t, 3J 7.5 Hz, 3 H), 1.25-1.55 (m, 12 H), 1.55 (quint, 3J7.5 Hz, 2 H), 1.S5 (quint, V7.5 Hz, 2 H), 4.15 (t, 3/7.5 Hz, 2 H), 7.20 (d, V S.5 Hz, 2 H), 7.25 (d, V 8.5 Hz, 6 H), 8.00-8.15 (m, 8H), 8.80-9.10 (m, 8 H). COMPOUND 39 5,10,15-tris-[4-(3-Trimethylammonio-propyloxy)-phenylJ-20-(4- decyloxy-phenyl)-porphyrin trichloride (Figure Remove)Compound 38 (50 mg, 0.061 mmol) and (1-brornopropyl)-triniethylammonium bromide (210 mg, 0.8 rnmol) are dissolved and K2C03 (230 mg, 1.7 mmol) is suspended in DMF (20 mL). The vigorously stirred reaction mixture is heated at 50°C for 18 h. After evaporation of solvent, the raw product is dissolved in methanol and purified by chromatography on a column (2.5 x 40 cm) of Sephadex, eluting with n-butanol:water:acetic acid (4:5:1, by vol., upper phase). After removal of the solvent, the residue is dissolved in methanol and passed through a column (3.5 x 20 cm) of Ambeiiite IRA-400 (chloride form). After evaporation of solvent, the product is dried under high vacuum and yields violet crystals. 'H-NMR: 8H (300MHz, CD3OD): 0.90 (t, 3J 7.5 Hz, 3 H), 1,20-1.40 (m, 12 H), 1.45-1.60 (bs, 2 H), 1.80-1.90 (bs, 2 H), 2.45-2.55 (bs, 6 H), 3.25-3.35 (bs, 27 H), 3.75-3.85 (bs,, 6 H), 4.05-4.25 (m, 2 H), 4.35-4.40 (bs, 6 H), 7.10-7.40, 7.95-8.15 (2 xrn, 16 H), 8.60-9.00 (bs, 8 H). COMPOUND 40 5,10,15-tiis-(4-Hydroxy-phenyl)-20-(4-tridecyloxy-phenyl)-porpliyiin (Figure Remove)5,10,15,20-tetralds~(4-Hydroxy-phenyl)-porphyrm (400 mg, 0.59 mmol) is dissolved and K2C03 (1.0 g, 7.1 mmol) is suspended in DMF (75 mL). To the vigorously stirred reaction mixture a solution of 1-bromotridecane (0.1 mL, 0.45 mmol) in DMF (10 mL) is added dropwise at 50°C during 30 mins and the mixture is then heated for l.Sh. The reaction mixture is cooled to room temperature and poured into water (150 mL). The porphyrins are extracted with ethyl acetate (100 mL) and the extract washed with brine (3 x 50 mL) and dried (Na2SC>4). After evaporation of solvent, the residue is dissolved in toluenetethanol (1:1, by vol., ca. 10 mL) and purified by chromatography using a column (200g) of silica gel (Merck 60) with toluene as the eluent. After the elution of the first three compounds, the eluent is changed to toluene:ethyl acetate (2:1, by vol.). The fifth compound eluted is collected and dried under high vacuum to yield product as violet crystals. 'H-NMR: 5H (SOOMz, d6-acetone): 0.85 (t, 3J7.5 Hz, 3 H), 1.20-1.60 (m, IS H), 1.50 (quint, V 7.5 Hz, 2 H), 1.80 (quint, 3J 7.5 Hz, 2 H), 4.14 (t, 3J 7.5 Hz, 2 H), 7.20 (d, 3/8.5 Hz, 2 H), 7.25 (d, 3J8.5 Hz, 6 H), 8.00-8.15 (m, 8H), 8.80-9.10(111, 8 H). COMPOUND 41 5-(4-Tridecyloxy-pheiiyl)-10,15,20-nis-[4-(3-trimethylammonio- prop3doxy)-phenyl]-porphyrin trichloride Compound 40 (50 mg, 0.057 mmol) and (1-broniopropyl)-triniethylanimonium bromide (210 mg, 0.8 mmol) are dissolved and K2C03 (230 mg, 1.7 mmol) is suspended in DMF (20 inL). The vigorously stirred reaction mixture is heated at 50°C for 18 h. After removal of DMF, the residue is dissolved in methanol (5mL) and applied to a pad (2 cm thick) of silica gel which is washed with methanol (ca. 1000 mL) and then eluted with acetic acid:methanol:water (3:2:1 by vol.). After evaporation of the solvent the residue is dissolved in methanol and further purified by chromatography on a column (2.5 x 40 cm) of Sephadex LH-20 which is eluted with n-butanol:water:acetic acid (4:5:1 by vol., upper phase). After removal of solvent, the residue is dissolved in methanol and passed through a short column (3.5 x 20 cm) of anion exchange resin (Amberlite IRC 400, chloride form). After evaporation of solvent, the product is dried under high vacuum to afford violet crystals, 5H (300MHz, CD3OD): 0.90 (t, V 7.5 Hz, 3 H), 1.20-1.40 (m, 18 H), 1.45-1.60 (m, 2 H), 1.80-1.90 (bs, 2 H), 2.40-2.55 (bs, 6 H), 3.25-335 (bs, 27 H), 3.75-3.85 (bs, 6 H), 4.05-4.25 (m, 2 H), 4.35-4.40 (bs, 6 H), 7.10-7.40, 7.90-8.15 (2 xm, 16 H), 8.60-9.00 (bs, 8 H). COMPOUND 42 5,15-bis-(4-Hydroxy-phenyl)-porphyrin (Figure Remove) This is prepared as described by Melita, Goverdhan; Muthusamy, Sengodagotmder; Maiya, Bhaskar G.; Arounaguiri, S.5 J.Chem.Soc.Perkin Trans. 1; 2177'-2182(1999). COMPOUND 43 5,10,15-tris-(4-Hydroxy-phenyl)-20-(4-octyloxy-phenyl)-porphyrin5,10,15.20-teti-alas-(4-Hydroxy-phenyl)-poiph}dn (200 mg, 0.294 mmol) is dissolved and potassium carbonate (487 mg, 3.53 mmol, 12 eqv.) is suspended under argon in absolute DMF (50 inL) and the mixture is heated to 55°C. A solution of octyl bromide (35.8jil, 0.206 mmol, 0.7 eqv.) in absolute DMF (10 mL) is added dropwise during 30 rain, and the mixture is stirred at 55°C for 2 h. The solvent is removed in vacua at 50°C, water (80 mL) is added and the mixture is extracted with ethyl acetate (3 x 40 mL). The combined organic fraction is dried (Na^SC^) and the solvent evaporated. The residue is purified by chromatography on a column (300g) of silica gel. Tetra-alkylated and tri-allcylated compounds are eluted with toluene:ethyl acetate (30:1 by vol.). The third fraction (di-substituted compound, trans-isomer) is eluted with toluene: ethyl acetate (15:1 by vol.). The fourth fraction (di-substituted compound, cis-isomer) is eluted with toluene:ethyl acetate (10:1 by vol.) and the desired product (mono-alkylated compound) is eluted with toluene:ethylacetate (5:1 by vol.). The solvent is removed under reduced pressure and the residue dried under high vacuum to give the product as a violet solid. 'H-NMR: 5H (300 MHz, d6-acetone): 0.75 (t, 3H, 3J= 6.8 Hz), 1.13-1.25 (m, SH), 1.43 (quint, 2H, 3/= 7.5 Hz), 1.73 (quint, 2 H, 3/= 7.5 Hz), 3.50 (t, 2H, 3J = 8 Hz), 7.11 (d, 2H, 3J = 7.5 Hz), 7.16 (d, 6 H, 3J= 7.5 Hz), 7.90-7.94 (m, 8H), 8.80-8.90 (m, 8 H) COMPOUND 44 5-(4-Dodecyloxy-phenyl> 10,15,20-tris-(4-hydroxy-phenyl)-porphyrin 5,10J15,20-tetralds-(4-Hydi-oxy-phenyl)-porphyrm (200 mg, 0.294 mmol) is dissolved and potassium carbonate (487 ing, 3.53 mmol, 12 eqv.) in suspended under argon in absolute DMF (50 mL) and the mixture is heated to 55°C. A solution of dodecyl bromide (49.4j.il, 0.206 minol, 0.7 eqv.) in absolute DMF (10 mL) is added dropwise during 30 min. The mixture is stirred at 55°C for 2 h. The solvent is removed in vacuo at 50°C, water (80 mL) is added and the mixture extracted with ethyl acetate (3 x 40 mL). The combined organic fractions are dried (Na2S04) and the solvent evaporated. The product is isolated by chroniatography on a column (300g) of silica. Tetra-alkylated and tri-alkylated compounds are eluted with toluene:ethyl acetate (30:1 by vol.), di-substinited compound (trans-isomer) with toluene:ethyl acetate (15:1 by vol.), di-substituted compound (cis-isomer) with toluene:ethyl acetate (10:1 by vol.) and the desired product (mono-alkylated compound) with toluene:ethyl acetate (5:1 by vol). Solvent is removed in vacuo and the residue dried at high vacuum to give product as a violet solid. LH-NMR: 8H (300 MHz, d6-acetone): 0.75 (t, 3H, 3J= 6.8 Hz), 1.13-1.25 (m, 16H), 1.41 (quint, 2H, 3J= 7.5 Hz), 1.63 (quint, 2 H, 3J= 7.5 Hz), 3.89 (t, 2H, 3J = 6 Hz), 7.11 (d, 2H, -J = 7.5 Hz), 7.16 (d, 6H, V= 7.5 Hz), 7.9-7.94 (m, 8H), 8.78-8,83 (m, 8 H) COMPOUND 45 5,10,15-tris-(4-Hydroxy-phenyl)-20-(4-nonyloxy-phenyl)-porpliyrin 5,10,15,20-tetralds-(4-Hydroxy-phenyl)-poiph}Tin (200 mg, 0.294 mmol) is dissolved and potassium carbonate (487 mg, 3.53 mmol, 12 eqv.) is suspended under argon in absolute DMF (50 mL) and the mixture heated to 55°C. A solution of nonyl bromide (49.4ul, 0.206 mmol, 0.7 eqv.) in absolute DMF (10 mL) is added dropwise during 30 min. The mixture is stirred at 55°C for 2 h. The solvent is removed in vacuo at 50°C, water (80 mL) is added and the mixture extracted with ethyl acetate (3 x 40 mL). The combined organic extracts are dried (Na2S04) and solvent removed under reduced pressure. The product is isolated by chromatography on a column (300g) of silica. Tetra-alkylated and tri-alkylated compounds are eluted with toluene:ethyl acetate (30:1 by vol.), di-substituted compound (trans-isomer) with toluene:ethyl acetate (15:1 by vol.). di-substituted compound (cis-isomer) with toluene:ethyl acetate (10:1 by vol.) and the desired product (mono-alkylated compound) is eluted with toluene:ethyl acetate (5:1 by vol.). The solvent is removed under reduced pressure and the residue dried at high vacuum to afford the product as a violet solid. 'H-NMR: 5H (300 MHz, d6-acetone): 0.87 (t, 3H, 3J= 7.5 Hz), 1.14-1.26 (m, 10H), 1.41 (quint, 2H), 1.70 (quint, 2H, lr= 7.5 Hz), 3.92 (t, 2H, 3/= 7.5 Hz), 7.02 (d, 2H, 3/= S.25 Hz,), 7.15 (d, 6H, 3J= 7.5 Hz,), 7.85 (d, 2H, 3/ = 8.25 Hz), 7.91 (d, 3J= 7.5Hz), 8.76-8,84 (m, 8 H) COMPOUND 46 5-(4-Octyloxy-phenyl)-10,15,20~tris-[4-(3-trimethylanmionio- propyloxy)-phenyl]-porphyrintricliloride Compound 43 (50 mg, 0.063 mmol) and (3-bromopropyl)-trimethylanimonium bromide (164mg, 0.63 mmol, lOeqv.) are dissolved and potassium carbonate (130 mg, 0.95 mmol3 15 eqv.) is suspended under argon in absolute DMF (30 mL) and the mixture is stirred at 55°C for 12 h. The solvent is removed in vacuo at 50°C and the residue applied to a pad (2 cm deep) of silica. The unreacted ammonium salts are washed off with methanol (lOOOmL) and the product is eluted with acetic acid:methanol:water (3:2:1 by vol.). The solvent is removed under reduced pressure and the residue further purified by chromatography on a column (lOOg) of Sephadex LH-20 using n-butanol:water:acetic acid (4:5:1 by vol., upper phase) as the eluent. The solvents are removed under reduced pressure and the residue dissolved in methanol and passed through a small column, of anion exchange resin (Amberlite IRA 400, chloride form) using methanol as eluent After evaporation of solvent, the crude product is dissolved in the minimum amount of methanol and diethylether (50 rnL) added. The solution is centrifuged for 15 mill. The supernatant liquid is evaporated to dryness and the residue dried at high vacuum to give the product as a violet solid. 'H-NMR: 6H (300MHz, CD3OD): 0.90 (t, 3H, 3J= 7.5 Hz), 1.25-1.41 (m, 8H), 1.45 (bs, 2H), 1.87 (bs, 2H), 2.38 (bs, 6H), 3,29 (bs, 27H), 3.67 (t, 6H, 3/= 7.5 Hz), 4.01 (t, 2H, 3J= 7.5 Hz), 4.30 (t, 6H, 3J= 7.5 Hz), 7.11 (d, 2H, 3J= 7.5 Hz), 7.38 (d, 6H, 3J= 7.5 Hz), 7.95 (d, 2H, 3J= 7.5 Hz), 8.11 (d, 6H, 3J=7.5Hz), 8.93 (bs, 8H) COMPOUND 47 5-(4-Dodecyloxy-phenyl)-10,15,2 0-tris-[4-(3-trimethylammonio- propyloxy)-phenyl]-porphyrin trichloride Compound 44 (50 mg, 0.059 mmoi) and (3-bromopropyl)-trimethylammonium bromide (154mg, 0.59 mmol, lOeqv.) are dissolved and potassium carbonate (122 mg, 0.885 mmol, 15 eqv.) is suspended under argon in absolute DMF (30 rnL) and the mixture is stirred at 55°C for 12 h. The solvent is removed in vacuo at 50°C and the residue re- dissolved in a little methanol and applied to a pad of silica (2 cm deep). The unreacted ammonium salts are washed off with methanol (lOOOmL). The product is eluted with acetic acid:methanol:water (3:2:1 by vol.). The solvents are removed under reduced pressure and the crude product further purified by cliromatography on a column (lOOg) of Sephadex LH-20 using n-butanol:water:acetic acid (4:5:1 by vol., upper phase) as eluent. The solvents are removed under reduced pressure, the residue re-dissolved in a little methanol and the solution passed through a short column of anion exchange resin (Amberlite IRC 400, chloride form) using methanol as eluent. After removal of solvent the crude product is re-dissolved in the minimum amount of methanol and diethyl ether (50 mL) added. The solution is centrifuged for 15 min. The supernatant liquid is evaporated to dryness and the product dried at high vacuum to give a violet solid. 'H-NMR: 8H (300MHz, CD3OD): 0.88 (t, 3H, 3J= 7.5 Hz), 1.25-1.37 (m, 16H), 1.48 (bs, 2H), 1.93 (bs, 2H), 2.42 (bs, 6H), 3,28 (bs, 27H), 3.68-3.75 (m, 6H), 4.05 (t, 2H), 4.33 (t, 6H), 7.17 (d, 2H, 3J= 7.5 Hz), 7.33 (d, 6H5 3J= 7.5 Hz), 7.99 (d, 2H, 3J= 7.5 Hz), 8.08 (d, 6H, 3J= 7.5 Hz), 8.85 (bs, 8H) COMPOUND 48 5-(4-Nonyloxy-phenyl)-l 0,15;20-tris-[4-(3-rrimethylammoiiio- propylox30-phenyl]-porplryrin trichloride Compound 45 (50 mg, 0.062 mmol) and (3-bromopropyl)-frimethylanmionium bromide (162mg, 0.62 mmol, lOeqv.) are dissolved and potassium carbonate (128 mg, 0.93 mmol, 15 eqv.) is suspended under argon in absolute DMF (30 mL) and the mixture is stirred at 55°C for 12 h. The solvent is removed in vacuo at 50°C and the residue re-dissolved in a little methanol and applied to a pad of silica (2 cm deep). The unreacted ammonium salts are washed off with methanol (lOOOmL). The product is eluted with acetic acid:methanol:water (3:2:1 by vol.). The solvents are removed under reduced pressure and the product further purified by chromatography on a column (lOOg) of Sephadex LH-20 eluting with n-butanol:water:acetic acid (4:5:1 by vol., upper phase). The solvents are removed under reduced pressure, the residue re-dissolved in a little methanol and the solution is passed through a short column of anion exchange resin (Amberlite IRC 400, chloride form) using methanol as eluent. After removal of solvent, the product is dried at high vacuum to give a violet solid. 'H-NMR: 5H (300MHz, CD3OD): 0.89 (t, 3H, 3J= 7.5 Hz), 1.18-1.34 (m, 10H), 1.41 (bs, 2H), 1.73 (quint, 2H, 3J= 1.5 Hz), 2.30-2.44 (m, 6H), 3,31 (bs, 27H), 3.65-3.73 (m, 6H), 3.93 (t, 2H, 3J= 7.5 Hz), 4.25-4.42 (m, 6H), 7.08 (d, 2H, 2J= 7.5 Hz), 7.30 (d, 6H, 3J= 7.5 Hz), 7.93 (d, 2H, 3J= 7.5 Hz), 8.05 (d, 6H, 3J= 7.5 Hz), 8.94 (bs, 8H) COMPOUND 49 5-(4-Octyloxy-phenyl)-10,15,20-tris- [4-(5-trimethylammonio-pentyloxy)- phenyl]-porphyrin trichloride Compound 43 (23 mg, 0.03 mmol) and (5-bromopenryl)-trimethylammonium bromide (84 mg, 0.3 mmol, lOeqv.) are dissolved and potassium carbonate (62 mg, 0.45 mmol, 15 eqv.) is suspended under argon in absolute DMF (15 mL) and the mixture is stirred at 55°C for 12 h. The solvent is removed in vacuo at 50°C and the residue re-dissolved in a little methanol and applied to a pad (2 cm deep) of silica. The unreacted ammonium salts are washed off with methanol (lOOOmL). The product is eluted with acetic acid:methanol:water (3:2:1 by vol.). The solvents are removed under reduced pressure and the product further purified by chromatography on a column (lOOg) of Sephadex LH-20 using n-butanol:water:acetic acid (4:5:1 by vol.. upper phase) as eluent. The solvents are removed under reduced pressure, the residue re- dissolved in a little methanol and the solution passed though a short column of aiiion exchange resin (Ambeiiite IRC 400, chloride form) with methanol as eluent. The complete purification process is repeated if impurities remain in the product. After removal of solvent, the residue is dried at high vacuum to give the product as a violet solid. JH-NMR: 6H (300MHz, CD3OD): 0.78 (bs, 3H), 1.08-1.35 (m, 10H), 1.45-1.59 (m, 6H), 1.63-1.93 (in, 14H), 3.17-3.32 (m, 6H), 3,31 (bs, 33H), 3.84 (bs, 2H), 4.07 (bs, 6H), 6.93 (bs, 2H), 7.09 (d, 2H, 3/= 7.5 Hz), 7.74 (bs, 2H), 7.88 (d, 2H, 3J= 7.5 Hz), 8.71 (bs, 8H) COMPOUND 50 5,10,15-1iis-[4-(5-Trimemylainmorjio-pentyloxy)-plienyl]-20-(4- undecyloxy-phenyl)-porphyrin trichloride Compound 2 (50 mg, 0.06 mmol) and (5-bromopentyl)-tiimethylammonium bromide (174 mg, 0.6 mmol, lOeqv.) are dissolved and potassium carbonate (124 mg, 0.9 mmol, 15 eqv.) is suspended under argon in absolute DMF (30 mL) and the mixture is stirred at 55°C for 12 h. The solvent is removed in vacuo at 50°C and the residue re-dissolved in a little methanol and applied to a pad (2 cm deep) of silica. The unreacted ammonium salts are washed off with methanol (lOOOmL). The product is eluted with acetic acidrmethanol:water (3:2:1 by vol.). Solvents are removed under reduced pressure and the product further purified by chromatography on a column (lOOg) of Sephadex LH-20 eluting with n-butanol:water:acetic acid (4:5:1 by vol., upper phase). Solvents are removed under reduced pressure, the residue re-dissolved in the minimum of methanol and the solution passed through a short column of anion exchange resin (Amberlite IRC 400) with methanol as eluent. The complete purification process is repeated if impurities remain in the product. After removal of solvent, the residue is dried at high vacuum to give the product as a violet solid. ]H-NMR: 6H (300MHz, MeOD): 0.71-0,88 (m, 13H), 0.91-1.38 (m, 14H), 1.48-1.81 (m, 12H), signals for -CH2NCH2 and OCH2-long alkyl chain are part of the multiplet together with the signals for solvent in the area 2.8-3.3, 3.91 (bs3 6H), 6.33 (bs, 2H), 6.86 (bs, 6H), 7.35 (bs, 2H), 7.70 (bs, 6H), 8.65 (bs, SH) COMPOUND 51 5,10,15,20-tetralds-(3-Dodecyloxy-phenyI)-porphyrin Pyrrole (0.7 mL, 10 rmnol) and S-dodecjdoxybenzaldehyde (2.91 g, 10 inmol) are dissolved in degassed dichloroniethane (1000 niL) and TFA (0.77 mL, 10 inmol) is added dropwise. The mixture is stirred for 17h at room temperature in the dark. DDQ (6.81 g, 30 mmol) is added in one portion and the mixture is stirred for a further Ih at room temperature. The mixture is filtered through a column (400g) of silica using dichloroniethane as eluent followed by dichloroniethane to which triethylamine is added to adjust the pH value to 8. This purification process is repeated if impurities remain in the product until the pure product is ohtained. 'H-NMR: 5H (300 MHz, d6-acetone): 0.80 (bs, 12H), 1.03-1.45 (m, 8OH), 1.78 (quint, 8H, 3J= 7.5 Hz), 4.05 (t, 8H, 3J= 7.5 Hz), 7.24 (d, 4H, 3J= 7.5 Hz), 7.49-7.55 (m, 4H), 7.68-7.71 (m, 8H), 8.80 (m, 8 H) example B: non-specific (dark toxicity) profiles and PHOTODYNAMIC ACTIVITY (LIGHT TOXICITY) PROFILES OF EXEMPLARY COMPOUNDS ON BACTERIAL CELLS Methodology The toxic effects of exemplary compounds of the invention against two bacterial strains, the Gram negative bacterium Escherichia coli (strain ATCC 25922) and the Gram positive bacterium Staphylococcus aureus (methicillin-resistant strain ATCCBAA-44), were evaluated by measuring the extent of growth inhibition (bacteriostatic effect) and growth inhibition (cytocidal effect) in the dark and upon light exposure. Initial compound screening was undertaken using white light [390 - n 740nm] (150 mW/cm ) for various timepoints at a concentration of 3uM (see Table 1). Further experiments were undertaken on those compounds identified from this initial screen using a light source emitting light at a wavelength between 417 - 420 nm at 15.2 niW/cm2, 13.68 J/cm2 (Waldmann Eclairage SA, France) (see Table 2). The following protocol was used for the initial screening of the exemplary compounds (Table 1) (see Reddi et al., 2002, Photochem. Photobiol. 75(5):462-470): (i) E. coli and S. aureus cells were grown overnight on brain heart infusion agar, resuspended in brain heart infusion broth, harvested by centrifugation (3000 g for 15 minutes) and washed once with phosphate buffered saline (PBS) at pH 7.4 containing 2.7 mM KC1 and0.14MNaCl. (ii) The cells were then resuspended in PBS to an optical density at r\ q 650 nm of 0.7, which corresponds to a density of 10 to 10 cells/ml. (iii) Next, the cells were incubated in PBS in the dark for 5 minutes with 3.0 pM of the compound to be tested. (iv) After dark incubation, cells were illuminated with white light (wavelength: 390 to 740 nm) (150 mW/cm2) for up to 30 minutes. During illumination, the cells were kept at 37DC and magnetically stirred. (v) Finally, treated and untreated (control) cells were diluted in brain heart infusion broth and maintained at 37°C while the absorbance of the suspension at 650 nm was monitored at predetermined time points for determining growth curves. The percent of growth inhibition in the treated cells was calculated by the following equation: [l-(Ax-A0)/(Ac-A0)]xlOO where Ax and Ac are the absorbances measured after 3 hours incubation: for the treated and control cell suspensions, respectively., and ao represents the initial absorbance. For the further investigation of the exemplary compounds (Table 2), the following protocol was adopted: (i) Bacteria (S. aiireus BAA-44 and E. coli 25922) were grown in brain heart infusion (BHI) broth until they reached the stationary phase of growth. (ii) The cells were harvested by centrifugation (3000 g for 15 min) with a table centrifuge, washed with 10 mM PBS at pH 7.4 containing 2.7 niM KC1 and 0.14 M NaCl and suspended in PBS at an optical density of 0.7 at 650 nm corresponding to 108-109 cells/ml. (iii) The bacteria, at the desired cell density (~108cells/ml) were incubated for 5 min in the dark with various concentrations of the exemplary compounds. (iv) At the end of the incubation period the cells were washed three times with PBS, suspended in PBS, transferred into a 96-well microtitre plate (200 jol/well) and illuminated for 15 min with the Waldmann light source (15.2 rnW/cm2; 13.7 J/cm2). The cells were illuminated from the bottom of tl^ ,:)> • laying it on the glass cover of the lamp. (v) After illumination, cell survival was determined by plating serially diluted aliquots of treated and untreated (i.e. no exemplary compound or light present) cells onto brain heart agar (BHA) and counting the number of colonies after 18-24 h incubation at 37°C. Table 1 Growth inllibition (%) ofE. coll and S. aureus cells irradiated with white light after 5 min incubation with selected test compounds at a concentration of 3 (iM. (Figure Remove) Results Results of the toxicity studies in E. coli and S. aureus are shown in Tables 1 and 2, together with Figures 2 and 3 (see Example A for compound, 'Cpd', structures). Table 2 Survival of E. coli and S. aureus cells after incubation with selected test compounds and illumination with white light ('photodynamic activity' or light toxicity) or no illumination ('dark toxicity') Conclusions The results demonstrate that the compounds of the invention, when illuminated with light, are capable of killing both gram positive and gram negative bacterial cells at the low concentrations investigated. Activity of Compound 10 at low doses The above colony forming unit (CPU) protocol was also used to investigate the photodynamic activity of very low concentrations of the compounds of the invention. For example, figure 4 demonstrates the results obtained using (A) Compound 8 and (B) Compound 10 in the presence (photodynamic properties) and in the absence (inherent toxicity properties) of light. Results (i) Compounds 8 and 10 both exhibited negligible dark toxicity against BAA-44 at the concentrations tested. (ii) Compound 8 exhibited a potent antibacterial effect at concentrations as low as 0.01 uM, where a 3 log reduction in BAA-44 was achieved. (iii) Compound 10 exhibited an even more potent antibacterial effect, causing a 3 log reduction in BAA-44 at a concentration of 0.005 and capable of killing 90% of the bacteria at a 0.0025 concentration. Conclusions Compounds 8 and 10 exhibit a dose-dependent and light-dependent toxicity against bacterial cells, even at very low doses. Range of antimicrobial activity The antibacterial activity of Compound 10 was tested against a range of bacterial strains: S. aureus ATCC BAA-44 (a methicillin resistant S. aureus) Ps. aeruginosa ATCC 25668 S. epidermidis ATCC 700565 Streptococcuspyogenes ATCC 49117 E. coli ATCC 25922 (Figure Remove)Conclusions Compound 10 exhibits photodynamic activity (i.e. light toxicity) against a broad range of gram positive and gram negative bacteiia. Photodynamic activity of Compound 10 against MRS A on ex vivo porcine skin Excised porcine skin was cut into 3(4) x 3(4) cm2 pieces under sterile conditions and incubated in 70% ethanol for 5 minutes to reduce background of colonised bacteria. After three washing steps in PBS, the skin pieces were fixed in petri dishes with Hepes-Agar. The epidermis (stratum corneum) was then inoculated with S. aureus ATCC BAA-44 (~10S, Volume: lOOul) and the skin surface dried under laminar flow cabinet until visible dry. The regions of interest were determined using a "pap" pen (1 cm2 diameter). A sterile solution of Compound 10 (10 fiM) was applied onto the skin for 10 minutes. Post application, the ex vivo porcine skin was placed under the Waldmann light source 236 and O 1 illuminated for 15 min (15.2 mW/cm , 13.7 J/cm ). A colony forming unit assay was performed to determine viable bacterial cell number immediately after irradiation using a sterile cotton rod to remove bacteria from the stratum corneum. The sterile cotton rod was moistened in sampling solution (0.1% TweenSO in 0.0075 M phosphate buffer pH 7.9) before swabbing the skin surface (3 times) and vortexed in sampling solution before undertaking serial dilutions to determine the bacterial recovery. Incubation with Compound 10 (10 uM) followed by 15 minutes irradiation resulted in a 3.2 Iog10 growth reduction (mean value of three target areas). In contrast, control experiments (irradiation of applied bacteria without Compound 10 incubation) did not show a decrease of bacteria cell number. Thus, these data demonstrate photodynamic activity of Compound 10 against MRS A on the surface of porcine skin, even in the presence of skin lipids and enzymes. Confirmation of photodynamic properties using sodium azide andD2O Quenching studies using D20 and azide were performed with Compound 10 and light against keratinocytes in vitro. In order to investigate whether phototoxicity of the test compound against NHDF, NHEK and bacteria follows the photo-oxidation type II, sodium azide, a physical quencher of singlet oxygen as well as D20, an enhancer of reactive oxygen species were used (Lin et al., 1991, Cancer .Res. 51:1109-1116; Moan et al, 1979, Brit. J. Cancer 39:398-407). Figure 5 shows the effect of incubation with Compound 10 and quencher or Compound 10 and D20 after illumination. Cell killing by Compound 10 was reduced in the presence of sodium azide, as indicated by an increase of the cell viability, whereas the addition of D2O revealed a dramatic decrease of cell viability. In conclusion, the killing of NHDF by Compound 10 with illumination appears to be mediated mainly by singlet oxygen and not by the compound itself. Acifte'toxicity testing of Compound 10 Compound 10 was used at a million times antibacterial dose (3.2 mM) in a topical formulation in a standard acute toxicity test to determine if any clinical or histological toxicity for the compound could be detected. The compound was applied to both intact and abraded rat skin for 24 hours. The acute toxicity protocol was based on OECD Guidelines for the testing of chemicals /Section 4. - Health Effects Test Number 402: Acute Dermal Toxicity. Results and Conclusions After clinical, macroscopic and microscopic observation, no clinical toxicology was observed. No histological toxicology of any major organ (including the skin) was observed. No cell infiltrates, including mast cells, were noted, neither was irritancy. In conclusion, Compound 10 does not result in any acute toxic or allergic effect: in fact, no significant clinical or pathological signs related to the substance and its vehicle application were observed. Photo-toxicity testing of Compound 10 The photo-toxicity protocol was based on OECD Guidelines for the testing of chemicals /Section 4 Health Effects - Test Number 406: Skin sensitisation. Preliminary experiments determined that a light exposure of 30 minutes did not result in any damage to the surface of the skin caused by the light source. Similarly, control experiments demonstrated that Compound 10 when applied at a concentration of 32 (iM in the absence of light did not result in any damage to the surface of the skin. The photo-toxicity of the Compound 10 in the topical formulation was studied when applied onto 14 Guinea Pig skin (intact and abraded) for 24 hours, followed by a 30 minute light exposure. Compound 10 was tested at two different concentrations 32 uM and 0.32 uM. Clinical and histological examination of the skin test sites was conducted at 24 and 72 hours post illumination in classical photo-toxicity testing fashion. Biopsies were not done from contiguous sites to prevent any interaction in case of suture. Gross findings were evaluated at the moment of the biopsy. Before giving a score to each endpoint (erythema, oedema and rnflamrnation), data for each subject were compared to the data from the other animals and to control data. A score from 0 to 4 was given for each site and for each endpoint according to the Draize Scale (for inflammation, a scale similar to the Draize Scale was created after microscopic observation of all skin sections, comparing with normal skin and with findings of step-1). A mean score was then calculated for each animal and for each sampling point. On analysing the results and comparing the experimental data with the data from the control animals, it was concluded that there were no clinical signs or symptoms or histological findings that suggested any photo-toxic potential of Compound 10. example Cr binding of exemplary compounds of the invention WITH BACTERIAL CELLS Binding of Compounds 8,10 and 12 with E. coli E. coli cells were incubated for 5 rain with. Compound 8, 10 or 12 at various concentrations (1-7.5 pM). At the end of the incubation period, the cells were sedimented by centrifugation. to remove the fraction of unbound test compound and the cell pellet was resuspended in 2 nil of 2% SDS to obtain cell lysates. After overnight incubation with SDS, the amount of cell-bound test compound was estimated by spectrofiuorimetric analysis of the cell lysates. The concentration of the compounds in the cell lysates was calculated by measuring the intensities at the maximum of the emission fluorescence spectrum and interpolating the data on a calibration plot. The amount of cell-bound test compound was expressed as nmoles of compound per mg of cell protein. The protein concentration was determined by the method of Lowry (Lowry et al, 1951, J. Biol Chem. 193:265-275). All experiments were run in triplicate and the results represent the average of 3 determinations with standard deviations. The amount of porphyrin recovered from the cells is shown in Table 4. Table 4 (Table Remove)The results shown in Table 4 show that the three test compounds bind to E. coli with similar efficiency and that about 50% of the compound that is associated to the cells at the end of the incubation period (5 min) is removed by 3 washings with PBS. example D: testing of exemplary compounds for emergence OF BACTERIAL RESISTANCE TO PDT The potential build up of resistance of the bacterial cells to the exemplary compounds of the invention was tested in the multi-drug resistant (including methicillin) gram positive bacterium Staphylococcus aureus BAA-44, using Compound 10 as the photodynamic agent. The survival of S. aureus BAA-44 after the second treatment was again compared to the survival of S. aureus BAA-44 cells that had not been treated with PDT, The same treatment was repeated for a total of 10 times in order to assess if the sensitivity of S. aureus BAA-44 cells to PDT remained constant or whether some resistance was observed to develop after repeated treatments. In an additional experiment, clones which had been exposed nine times to PDT treatment by the above methodology were treated for a tenth time and the results compared to the cell kill observed in a parallel experiment where naive cultures (i.e. which had not been exposed to PDT) were subjected to PDT treatment under exactly the same conditions. The results obtained after 10 subsequent PDT treatments are shown in Figure 6. The results obtained from comparing cell kill obtained from cultures that had been exposed to 10 consecutive PDT treatments with na'ive cultures (i.e. winch had not been exposed to PDT) are shown in Figure 7. The survival was expressed as log No/N, where no and N represent the number of CFU/ml of the untreated and treated cell suspensions. Statistical analysis by T test demonstrated that the differences between the 2 values were not significant (P > 10%): Conclusions The photosensitization of S. aureus ATCC BAA-44 by Compound 10 induced no appreciable development of resistance. In fact, the efficiency of photodynamic activity of Compound 10 remained unchanged in ten subsequentphotodynamic sequence sessions, even though bacterial cells, which were exposed in the previous treatments, were cultivated and re-exposed to Compound 10 and light. Therefore, treatment of bacteria using Compound 10 in a photodynamic fashion is further enhanced by the apparent lack of induction of bacterial resistance, unlike antibiotic therapies, where multi-drug resistance is a significant issue. example E: toxicity profile - selectivity of exemplary COMPOUNDS FOR BACTERIA Methodology Test compounds were screened for toxicity against cultured human skin cells using normal human epidennal Iceratinocytes (NHEK) and normal human dermal fibroblasts (NHDF), purchased from CellSystems Biotechnologie GmbH, Germany. The NHEK and NHDF cells were used between passages 3 and 10. The cells were seeded with 7.5 and/or 15 x 104 cells/ well (microtitreplate) and were allowed to attach overnight in an incubator (37°C, 5% CO2). After incubation with different concentrations of the selected photosensitisers, the cells were illuminated for fifteen minutes (Light source 236, Waldmann; 15.2 mW/cm2, 13.7 J/cm2) and then incubated for 24 hours in the dark. Phototoxicity was tested by standard MTT-assay (Mossman et al, 1983, Immunological Methods 65:55-63). MTT is an indicator of metabolically active cells. Dependent on enzyme activity in mitochondria a colour reaction can be visualised, which can be measured by ELISA reader (540 urn). The cell viability data were normalised, i.e. the OD values of cells after PDT without photosensitisers were adjusted to one. Each experiment was repeated three times. Results Results of the toxicity studies in keratinocytes and fibroblasts are shown in Table 5. TABLES Survival of keratinocyte and fibroblast cells after incubation with selected test compounds and illumination ("photodynamic activity7) or no illumination ('darktoxicity') (A) Table 5- continued Figure 8 shows the toxicity of Compound 8 against human fibroblasts and S. aureus BAA-44 at varying doses. Conclusions The above data demonstrate that compounds of the invention, for example Compound 8 (at a dose of 0.01 uM), Compound 12 (at a dose of 0.1 uM) and Compound 10 (at a dose of 0.01 uM), are preferentially toxic to bacterial cells compared to human skin cells. In contrast, reference Compound 1 exhibits equal toxicity to "bacterial and human cells. example F: stability studies Methodology A "bespoke light source capable of delivering light of an appropriate wavelength (417 nm) was developed to activate the test compounds (Waldmaira light source 236). The light source has a light intensity of 15 mW/crn2 after 3 minutes at room temperature (25 °C), yielding a light dose of 14 J/cm2. It consists of a light box (493mm length x 278mm width x 93.3 mm height) where the samples to be tested are placed on the top surface of the light box and illuminated from below. Photostability of Compound 10 The photostability of the exemplary compounds was investigated using standard photodynamic procedures. A 10 uM solution of Compound 10 was prepared in phosphate-buffered saline/ethanol, as described above, and illuminated with blue light (15 mW/crn2} using a light source with an absofbance maximum of 417 nm. The solution was illuminated for various periods: 10, 20 and 30 minutes. After each predetermined illumination period, the absorbance at 404 run corresponding to the maximum absorption peak of the compound was measured. Parallel experiments were undertaken where the absorbance of Compound 10 solutions that had been kept in the dark for the same time periods as the. illumination time periods were measured. Over the 30 minutes period of illumination a small loss in the absorbance value at 404 rim was observed (see Figure 10 A). The susceptibility of the Compound 10 to photobleaching when subjected to a light at a higher fhience rate (150 mW/cm"; i.e. ten times that used normally) was investigated. With this illumination system, the solution was kept in a quartz cuvette during illumination while an equivalent solution was kept in the dark. The reduction of absorbance caused by photobleaching was found to be approximately 15-20 % at a concentration of 10 uM after 30 minutes illumination (see Figure 10B). The above results indicate that Compound 10 undergoes photobleaching much less than other porphyrins known in the literature (for example, see Reddi et al, 2002, Photochem. Photobiol. 75:462-470). Chemical stability The following HPLC methodology was established for the analysis of the exemplary compounds of the invention. The method involves detection by UV at a wavelength of 420 nm, which is very specific for these compounds. In order to monitor impurities not related to the porphyrin structure (and therefore not absorbing at 420 nm.) UV spectra of the whole chromatograms were also recorded between 200 nm and 700 nm by DAD (diode array detector) in certain experiments. Column: Eluent A: EluentB: Zorbax Phenyl, 250 x 4.6 mm, 5 |_im 1.5 g sodium dodecylsulfate + 1 ml, formic acid in 1000 mL water 1.5 g sodium dodecylsulfate + 1 mL formic acid in 200 mL water + 800 mL tetrahydrofurane Gradient: Flow rate: Detection: Column temperature: Injection volume: 0.4mL/min 420 nrn 25 °C 10 ul Solutions: Porphyrin derivatives were dissolved in eluent A to give a final concentration of approximately 0.3 mg/ml. Typical retention time of the exemplary compounds was approximately 8 minutes (18 minute runtime). Qualitative stress tests were undertaken on the exemplary compounds of the invention. Analysis was undertaken by HPLC & LC-MS. The compounds were stress tested in solid form, in an aqueous solution and a solution made up in phosphate-buffered saline buffer. The samples were initialty incubated for 7 days at 50 °C and a sample removed for testing. The samples were then incubated for a further 7 da)'s at 70 °C, samples removed as before and the samples incubated further for 7 days at 90 °C. HPLC analysis of freshly prepared solutions was undertaken and compared to the samples after 7, 14 and 21 days incubation. A visual comparison of the chromatograms was then undertaken and the content of the main products and by-products as area percentage values determined (see Figure 11). The 3D plots of the chromatograms show no indications for additional formation of fragments (no signals at lower wavelengths) The plot in Figure 12 shows the sample after 21 days in PBS buffer, which showed the largest degradation effect. The results demonstrated minimal degradation on analysis of solid drug and drug in solution heated to 80°C for a number of weeks. Conclusions Compounds 10 and 12 were both found to exhibit good stability and were very stable even under the stressed conditions of the test protocol. Although Compound 8 was less stable than Compounds 10 and 12, the stability demonstrated was found to be sufficient for practical use. Stability of exemplcny compounds in formulations The stability of three exemplary compounds of the invention (Compounds 8, 10 and 12) and one reference compound (Compound 1), stored at 40°C in the dark over 8 weeks in polyethylene vials in various aqueous-based formulations, was evaluated as follows: Sodium laureth sulphate (SLES) + water 9:1 water rethanol SLES+ 9:1 water: ethanol UV spectra were recorded over the range 350-700 mn over a period of 7 weeks and a visual evaluation of the samples made at 8 weeks. The results indicate that all compounds tested exhibited good stability over an eight-week period (see Figure 13). For Compounds 8 and 10, the stability study was extended to 17 weeks (see Figure 14). example G: distribution studies Human skin distribution Human skin (intact) in Franz cell system was used to examine the distribution of Compounds 10 and 12 within skin compartments after 22 hours incubation at high concentration. Three separate experiments, each using one skin sample (from the same donor) was undertaken per formulation. 250ul of each formulation was applied under occlusion and removed after 22 hours. Skin was separated and the compound content in stratum comeum, epidermis and dermis, and receiver solution determined using HPLC. The following HPLC methodology was established for the analysis of the exemplary compounds of the invention: HPLC system details: TSP SCM1000 membrane degasser, P4000 quaternary pump, AS3000 autosampler, UV6000LP UV/Vis PDA detector, SN4000 controller, PC1000 Ver. 3.5.1 software. Zorbax SB-Phenyl, 5 jim, 250 x 4.6 mm column plus a Phenyl security guard cartridge (Phenomenex). Mobile phase: 550 mL water; 450 mL tetrahydroruran; 1.5 g sodium dodecyl sulfate and 1 mL formic acid at a flow rate of 0.8 mL/rnin. Injection volume was 50 uL (foil loop injection) and operating temperature was 25°C. Detector was set at a wavelength of 409 mn plus UV/Vis scan (240-752 nm, step 4 run). Typical retention time of the exemplary compounds was approximately 8 minutes (18 minute runtime). The majority of the compounds associated with the skin were found to reside in stratum comeum. Low concentrations were detected in the epidermis (approx. 0.01 uM) - i.e. potentially anti-bacterial concentration. Lower concentrations were detected in the dermis (approx. 0.002 p.M). Compounds were not detected in the receiver solution The key findings are as follows: (i) The vast majority of Compound 10 was recovered from the surface of the stratum corneum. (ii) Much lower, yet potentially antibacterial, concentrations of Compound 10 were recovered within the stratum corneum. (iii) In the absence of ethanol, sub-therapeutic concentrations of Compound 10 were found in the epidermis and dermis. (iv) In the presence of ethanol, higher concentrations of Compound 10 were found in the epidermis, (v) No formulation led to a potentially antibacterial concentration of Compound 10 reaching the dermis. (vi) The formulations containing SLES were the only ones in which Compound 10 was detected at very low concentration in the receptor phase. (vii) Compound 10 distribution in the skin can, to a certain degree, be manipulated by the formulation used. Human Skin Cell Distribution: imaging studies The sub-cellular distribution of the dyes in human dermal fibroblasts -(NHDF) and human dermal keratinocytes (NHEK) has been investigated. NHDF were grown on microscope slides overnight and the cells were then incubated with Compound 10 for 5 minutes, 1 and 4 hours alone or incubated cells were co-stained with organelle-specific dyes. For labelling of lysosomes and mitochondria LysoTrackerGreen (Molecular Probes) and Rhodamine G6 (Sigma) were used, respectively. Immediately after incubation sub-cellular localisation was examined b}' fluorescence microscopy (Zeiss Vario AxioTech. Germany) using an appropriate dual band filter set (Omega Optical) for excitation and emission. Using a suitable software application, it is possible to overlay digital photographs (fluorescence) onto light microscopy photographs transparently. Therefore distribution of the dyes can be localized by one image. In addition, overlay of several digital photographs using different colour-images is also possible. NHDF cells were grown overnight on microscope slides. After that, the cells were incubated with 1 uM Compound 10 (green fluorescence) for 1 hour and co-stained with (A) organelle-specific dyes for mitochondria (Rhodamine G6; 50 ng/ml, 5 minutes; red fluorescence) and nucleus (Hoechst 33342; blue fluorescence) or (B) organelle-specific dyes for lysosomes (LysoTrackerGreen; 10 jiM, 2 h; green fluorescence) and nucleus (Hoechst 33342; blue fluorescence). Sub-cellular localisation was examined by fluorescence microscopy (Zeiss Vario AxioTech, Germany) using an appropriate dual band filter set (Omega Optical) for excitation and emission. Co-localisation is merged in yellow fluorescence. Staining of (A) lysosymes and (B) mitochondria without co-staining is shown in Figure 15. Figure 16 shows the intracellular fluorescence distribution of NHDF cells incubated with 1 uM Compound 10 for 1 hour. The Compound 10 fluorescence is localised extra-nuclearly and co-staining with mitochondria-specific Rhodamine G6 resulted in co-localisation of Compound 10 (green) and fluorescence of mitochondria (red). Co-localisation is merged in yellow fluorescence (Figure 16). Co-staining with lysosomal-specific dye (LysoTrackerGreen) resulted in different localization of Compound 10 (red) and lysosomal fluorescence (green) (Figure 16). Conclusions No nuclear association of Compound 10 was observed in nuclear material in these studied which may indicate that there is a low possibility of compound activity against DNA. WE CLAIM; 1. A cationic porphyrin compounds of formula I (Formula Removed) wherein: X1, X2, X3 and X4 independently represent a hydrogen atom, a lipophilic moiety, a phenyl group, a lower alkyl, alkaryl or aralkyl group, or a cationic group of the following formula: -L-R1-N+(R2)(R3)R4 wherein, L is a linking moiety or is absent; R1 represents lower alkylene, lower alkenylene or lower alkynylene, which is optionally substituted by one or more substituents selected from lower alkyl, lower alkylene (optionally interrupted with oxygen), fluoro, OR5, C(0)R6, C(0)OR7, C(0)NR8R9, NR10R11 and N+R12R13R14; and R2,R3 and R4 independently represent H, aryl, lower alkyl, lower alkenyl or lower alkynyl, the latter three of which are optionally substituted by one or more substituents selected from lower alkyl, lower alkylene (optionally interrupted with oxygen), aryl, OR5, C(0)R6, C(0)OR7, C(0)NR8R9, NR10R11 and N+R12R13R14 Z is -CH or N; and Y1, Y2, Y3 and Y4 are absent or independently represent aryl, lower alkyl, lower alkenyl or lower alkynyl, the latter three of which are optionally substituted by one or more substituents selected from lower alkyl, lower alkylene (optionally interrupted with oxygen), aryl, OR5, C(0)R6, C(0)OR7, C(0)NR8R9, NR10R11 and N+R=2R13R14; and R5, R6, R7, R8, R9, R10, R11, R12, R13 and R14 independently represent H or lower alkyl M represents two H atoms on opposing nitrogen groups or is a metallic element or metalloid element provided that at least one of X1, X2, X3, and X4 is a cationic group as defined above and at least one of X1, X2, X3, and X4 is a hydrogen atom. 2. A compound as claimed in claim 1 wherein M is a metallic element or a metalloid element and X1, X2, X3, X4, Y1, Y2, Y3, Y4 and Z are as defined in Claim 1. 3. A compound as claimed in claim 2 wherein M is a divalent or trivalent metallic element. 4. A compound as claimed in claim 2 or 3 wherein M is selected from Zn (II), Cu (II) La (III), Lu(III), Y (III), In (III) Cd (II) Mg (II) Al(III), Ru, Ni(II) Mn(III) Fe(III) and Pd(II). 5. A compound as claimed in claim 2 wherein M is a metalloid element, for example silicon (Si) or gemanium (Ge). 6.A compound as claimed in any one of the preceding claims wherein Y1, Y2, Y3 and Y4 are absent. 7.A compound as claimed in any one of the preceding claims wherein Z is -CH. 8.A compound as claimed in any one of the preceding claims wherein Ri is an unsubstituted lower alkylene, lower alkenylene or lower alkynylene group. 9.A compound as claimed in any one of the preceding claims wherein Ri is - (CH2)m-. and 'm' is an integer between 1 and 20. 10A compound as claimed in claim 9 wherein 'm' is an integer between 1 and 10, for example between 1 and 6, between 1 and 5, between 1 and 4 or between 1 and 3. 11.A compound as claimed in claim 10 wherein 'm' is 3. 12.A compound as claimed in any one of the preceding claims wherein R2, R3 and/or R4 are lower alkyl, lower alkenyl or lower alkynyl groups. 13.A compound as claimed in claim 12 wherein R2, R3 and/or R4 are unsubstituted lower alkyl groups. 14.A compound as claimed in claim 12 or 13 wherein at least one of R2, R3 and R4 is an alkyl group which is substituted with a primary, secondary or tertiary amine group or a quaternary ammonium group. 15.A compound as claimed in any one of the preceding claims wherein R is -(CH2)3-, R2 and R3 are CH3 and R4 is -(CH2)3-N(CH3)2. 16. A compound as claimed in any one of the preceding claims wherein R1 is -(CH2)3-, and R2, R3 and R4 are each CH3. 17. A compound as claimed in any one of the preceding claims wherein Ri is -(CH2)3-, and R2, R3 and R4 are each C2H5. 18. A compound as claimed in claim 1 wherein L is selected from the group consisting of phenoxy, phenylene, sulfonyl amido, aminosulfonyl, sulfonylimino, phenylsulfonyl- amido, phenylaminosulfonyl, urea, urethane and carbamate linking moieties. 19. A compound as claimed in claim 1 wherein X1, X2, X3 and/or X4 are: (Formula Removed) wherein R is -R1-N+(R2)(R3)R4, as defined in Claim 1 and 'n' is an integer between 1 and 3. 20. A compound as claimed in claim 1 wherein X1, X2, X3 and/or X4 are: (Formula Removed) wherein R is -R1-N+(R2)(R3)R4, as defined in Claim 1 and 'm' is an integer between 1 and 3. 21. A compound as claimed in claim 1 wherein X1, X2, X3 and/or X4 are: (Formula Removed) wherein R is -R1-N+(R2)(R3)R4, as defined in Claim 1 and 'n' and 'm' are integers between 1 and 3 and wherein the sum of 'n' and 'm' is an integer between 1 and 3. 22. A compound as claimed in any one of claims 19 to 21 wherein n' or `m' is 3. 23. A compound as claimed in any one of claims 19 to 21 wherein 'n' or `m' is 2. 24. A compound as claimed in any one of claims 19 to 21 or 23 wherein `n' and/or 'm' is 1. 25. A compound as claimed in any one of the preceding claims wherein at least one of X1, X2, X3 and X4 is a lipophilic moiety. 26. A compound as claimed in claim 25 wherein the lipophilic moiety is a saturated, straight-chain alkyl group of formula - (CH2)P CH3 wherein 'p' is an integer between 1 and 22. 27. A compound as claimed in claim 1 to 24 wherein 'p' is between 1 and 18, for example between 2 and 16 or between 4 and 12. 28. A compound as claimed in any one of claims 1 to 25 wherein none of X1, X2, X3 and X4 is a lipophilic moiety. 29. A compound as claimed in any one of the preceding claims wherein none of X1, X2, X3 and X4 is a phenyl roup. 30. A compound as claimed in claim 1 wherein the compound is 5, 15-bis-(4-{3-[(3-Dimethylamino-propyl)-dimethyl-ammonio]propyl-oxy}-phenyl)-porphyrin dichloride. 31. A compound as claimed in claim 1 wherein the compound is 5, 15-bis-[4-(3-Trimethylammonio-propyloxy)-phenyl]-porphyrin dichloride. 32. A compound as claimed in claim 1 wherein the compound is 5, 15-bis-[3-(3-Trimethylammonio-propyloxy)-phenyl]-porphyrin dichloride. 33. A compound as claimed in claim 1 wherein the compound is 5,15- bis-[4-(3-Trimethylammonio-propyloxy)-phenyl]-porphyrin dichloride. 34. A compound as claimed in claim 1 wherein the compound is 5-[3,5-bis-(3-Trimethylammonio-propyloxy)-15-undecyl-porphyrin dichloride. 35. A compound as claimed in claim 1 wherein the compound is 5-{4-[3-Dimethyl-(3-dimethyiaminopropyl)-ammonio-propyl-oxy]-phenyl}-15-(4-dodecyloxy-phenyl)-porphyrin chloride. 36. A compound as claimed in claim 1 wherein the compound is 3-[({3-[(3-{4-{15-(4-Dodecyloxy-phenyl)-porphyrin-5-yl]-phenoxy}-propyl)-dimethyl-ammonio]-propyl}-dimethyl-ammonio)trimethyl-ammonium trichloride. 37. A compound as claimed in claim 1 wherein the compound is 5,15-bis-[3- (3-Trimethylammonio-propyloxy) -phenyl] -10-undecyl-porphyrin dichloride. 38. A compound as claimed in claim 1 wherein the compound is 5-{4-{3 Dimethyl-(3-trimethylammonio-propyl)-ammonio-propyloxy]-phenyl}- 15-(4-dodecyloxy-phenyl)-porphyrin dichloride. 39. A compound as claimed in claim 1 wherein the compound is 5-{4-(3- Dimethydecyl-ammoniopropyloxy) -phenyl]-15-4-[3-dimethyl-(3- dimethylaminopropyl) -ammoniopropyloxy] -phenyl}-porphrin dichloride. 40. The compound as claimed in any one of the preceding claims as and when used in the form of a sterilizing solution optionally in the presence of a surface-active agent of the kind such as herein described. 41. A method for killing microorganisms in vitro comprising contacting the microorganisms with a compound as claimed in any one of claims 1 to 39 and illuminating the compound to kill the microorganisms. 42. A compound substantially as hereinbefore described with reference to the description. 43. A method for killing microorganisms in vitro substantially as hereinbefore described with reference to the description.

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