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Previous studies (Biolo et al., Photochem. Photobiol. 59, 362-365, 1994) showed that liposome-delivered Si(IV)-naphthalocyanine (SiNc) photosensitizes B16 pigmented melanoma subcutaneously transplanted in C57 mice to the action of 776 nm light. However, the efficacy of the phototreatment was limited by a lack of selectivity of tumor targeting by SiNc as well as by incomplete necrosis of the neoplastic mass. The present investigations show that the use of a different delivery system (Cremophor emulsion vs liposomes of dipalmitoylphosphatidylcholine) causes no significant increase in the selectivity of tumor targeting for three injected doses of SiNc (0.5, 1, 2 mg/kg). However, upon 776 nm light irradiation (300 mW/cm2; 520 J/cm2), the delay in the rate of tumor growth was maximal (7-8 days) for the highest naphthalocyanine dose. On the other hand, a remarkable improvement in the tumor response was obtained by inducing an intratumoral temperature increase to 44 degrees C immediately after PDT. The thermal effect appeared to be due to photoexcitation of melanin by 776 nm light (550 mW/cm2; 520 J/cm2) and subsequent partial conversion of absorbed energy into heat.

—Bis(di-isobutyl octadecylsiloxy)silicon 2,3-naphthalocy-anine (isoBOSINC) is a representative of a group of naphthalocyanine derivatives with spectral and photophysical properties that make them attractive candidates for photodynamic therapy (PDT). Tissue distributions were studied in tumor-bearing rats as a function of delivery system and time following administration. The tumor model was an N-(4-[5-nitro-2-furyl]-2-thiazolyl) formamide (FANFT)-induced urothelial cell carcinoma transplanted into one hind leg of male Fischer 344 rats; isoBOSINC was delivered to the rats by intravenous injection of 0.50 mg/kg of body weight as a suspension either in 10% Tween 80 in saline (Tween) or 10% (Cremophor® EL + propylene glycol) in saline (Cremophor). The isoBOSINC was isolated from several tissues and organs, as well as tumors and peritumoral muscles and skin. Quantitation was by a high-performance liquid chromatographic technique with detection that utilizes the native fluorescence of the naphthalocyanine derivative. Independent of the delivery system, the dye was retained in tumors at higher concentrations than in normal tissues, except for spleen and liver. The isoBOSINC retention in tumors was high and was vehicle dependent. For Tween, the maximal ratio of dye in tumor versus peritumoral muscle occurred 12 h after injection; for Cremophor, the maximal ratio occurred later, 336 h postinjection. When the drug was delivered in Tween, isoBOSINC in serum showed two compartment kinetics: half-lives of about 2 and 11 h were found for the distribution and the elimination phases, respectively. When Cremophor was the vehicle, the elimination half-life was about 20 h, and one compartment kinetics was observed. The latter findings may explain the generally higher levels of the dye attained by the tissues at later times with Cremophor as the vehicle. An interesting exception wasthat after 7 and 14 days postinjection in Tween, the levels of dye found in testes were six- to seven-fold higher than those found after Cremophor delivery. Levels of dye were very low or not detectable in the brain. Optimal parameters for PDT of tumors with this novel photosensitizer are clearly time- and vehicle-dependent, and future PDT studies will need to incorporate these modulators.

Bis(di-isobutyl octadecylsiloxy)silicon 2,3-naphthalocyanine (isoBOSINC) is a representative of a group of naphthalocyanine derivatives with spectral and photophysical properties that make them attractive candidates for photodynamic therapy (PDT). Tissue distributions were studied in normal and in tumor-bearing rats as a function of time following intravenous injection of isoBOSINC as a suspension in 10% Tween 80 in saline. The dose studied was 0.25 mg/kg of body weight. The compound isoBOSINC was isolated from several tissues and organs, as well as tumors and peritumoral muscles and skin, and quantitated by a high-performance liquid chromatographic technique. The tumor model, an N-(4-[5-nitro-2-furyl]-2-thiazolyl)formamide (FANFT)-induced urothelial cell carcinoma, was transplanted into the hind legs of Fischer 344 rats. The dye was retained in tumors at higher concentrations than in all tissues and organs examined, except for spleen and liver. The highest concentration ratio of dye in tumor versus peritumoral muscle (24.5) occurred 9 h after injection. Serum clearance of isoBOSINC showed similar kinetic behavior for both groups of rats, with a t 1/2 of elimination of approximately 10 h. At 7 and 14 days postinjection, the levels of dye found in testes were generally higher than in most other tissues, except spleen and liver. Concentrations of isoBOSINC were either very low or not detectable in rat brain. Trace amounts of the dye were excreted in the urine, and by day 14 approximately 17% of the dose was accounted for in the feces. The significant levels of the drug in tumors, as well as the excellent ratios of tumor-to-muscle concentration observed, have promising implications for PDT of tumors.

The palladium complex of 1,6,10,15,19,24,28,33-octabutoxynaphthalocyanine, PdNc(OBu) 8 , is shown to undergo reversible addition of O 2 in benzene solution at ambient temperature (22±1 o C) during steady-state photolysis with an Ar ion laser. On the basis of 1 H-NMR and electronic absorption spectral evidence, the photoadduct is postulated to be an endoperoxide which has molecular oxygen added to one of the benzene rings at the sites a to the point of fusion with the tetrapyrrole ring, i.e., the positions bearing butoxy substituents. The formation of this product probably involves O 2 ( 1 Δ g )

Photodynamic therapy (PDT) of cancer is a modality that relies upon the irradiation of tumors with visible light following selective uptake of a photosensitizer by the tumor tissue. There is considerable emphasis to define new photosensitizers suitable for PDT of cancer. In this study we evaluated six phthalocyanines (Pc) for their photodynamic effects utilizing rat hepatic microsomes and human erythrocyte ghosts as model membrane sources. Of the newly synthesized Pc, two showed significant destruction of cytochrome P-450 and monooxygenase activities, and enhancement of lipid peroxidation, when added to microsomal suspension followed by irradiation with approximately 675 nm light. These two Pc named SiPc IV (HOSiPcOSi[CH3]2[CH2]3N[CH3]2) and SiPc V (HOSiPc-OSi[CH3]2[CH2]3N[CH3]3+I-) showed dose-dependent photodestruction of cytochrome P-450 and monooxygenase activities in liver microsomes, and photoenhancement of lipid peroxidation, lipid hydroperoxide formation and lipid fluorescence in microsomes and erythrocyte ghosts. Compared to chloroaluminum phthalocyanine tetrasulfonate, SiPc IV and SiPc V produced far more pronounced photodynamic effects. Sodium azide, histidine, and 2,5-dimethylfuran, the quenchers of singlet oxygen, afforded highly significant protection against SiPc IV- and SiPc V-mediated photodynamic effects. However, to a lesser extent, the quenchers of superoxide anion, hydrogen peroxide and hydroxyl radical also showed some protective effects. These results suggest that SiPc IV and SiPc V may be promising photosensitizers for the PDT of cancer.

Alkyner are oxidized by oxo(salen)chromium(V) triflate and related complexes 2 to form 1,2-diones. The oxidation of diphenylacetylene proceeds by formation of an intermediate which reacts more rapidly with a second equivalent of oxometal complex to form benzil. The intermediate is most likely a metallaoxetene or a related species, such as a metallocarbene. Reactions of phorphorus or nitrile ylides with 2 proceed to form carbonyl compounds (and phosphine oxide or nitrile) in a manner consistent with participation of Similar intermediates. The reactions appear to be related mechanistically to alkene epoxidation by the same oxometal complexes

Alkyner are oxidized by oxo(salen)chromium(V) triflate and related complexes 2 to form 1,2-diones. The oxidation of diphenylacetylene proceeds by formation of an intermediate which reacts more rapidly with a second equivalent of oxometal complex to form benzil. The intermediate is most likely a metallaoxetene or a related species, such as a metallocarbene. Reactions of phorphorus or nitrile ylides with 2 proceed to form carbonyl compounds (and phosphine oxide or nitrile) in a manner consistent with participation of Similar intermediates. The reactions appear to be related mechanistically to alkene epoxidation by the same oxometal complexes

The synthesis and the properties of 1,4-dibutoxy-2,3-dicyanotriptycene, of a metal-free tetradibenzobarrelenooctabutoxyphthalocyanine, and of the corresponding zinc phthalocyanine are described. The two phthalocyanines do not aggregate when dissolved in benzene at concentrations up to 450 microM. For the metal-free and the zinc compounds, the red band maxima are at 736 and 757 nm, the triplet maxima are at 590 and 605 nm, the triplet state lifetimes are 58 and 177 microseconds, and the protoporphyrin-IX dimethyl ester-to-compound bimolecular rate constants for triplet energy transfer are 2.61 x 10(8) and 1.47 x 10(8) M-1 s-1. Triplet energy transfer from the metal-free compound to O2 is endoergonic by 1.0 kcal mol-1. The potential of the zinc compound for photodynamic therapy is touched upon.

When a dilute F- solution was added to a culture of Chinese hamster cells that had been preincubated with an aluminium phthalocyanine sensitizer derived from AlPcCl, the photosensitivity of the cells was markedly reduced compared to control cells not treated with F-. Under the same treatment conditions, the reduction in [3H]thymidine incorporation into cellular DNA caused by light and this sensitizer and the production of DNA-protein crosslinks caused by light and this sensitizer were also inhibited by F-. In contrast, the killing of Chinese hamster cells, the reduction of thymidine incorporation by the cells, and the production of DNA-protein crosslinks in the cells caused by the combination of light and either Photofrin II or the silicon phthalocyanine HOSiPcOSi(CH3)2(CH2)3-N(CH3)2 were not inhibited by F-. We conclude that the aluminium phthalocyanine sensitizer used is largely or completely AlPc(OH)(H2O), that it is converted to a fluoro complex by F-, and that this compound probably is a less efficient generator of photochemical damage at a critical cellular target(s) than is AlPc(OH)(H2O). The inhibition of thymidine incorporation and DNA-protein crosslink formation indicates that the effects of F- can be expressed at intracellular sites. It is further concluded that the silicon phthalocyanine sensitizer and Photofrin II do not interact significantly with F-.

Bis(di-isobutyl octadecylsiloxy)silicon 2,3-naphthalocyanine (isoBOSINC) is a synthetic potential photosensitizer for tumor therapy. A new method, which combines solvent extraction and several purification steps, has been developed to determine its presence in tissues. Separation and quantitation of isoBOSINC is done by high-performance liquid chromatography on a silica column with toluene as a mobile phase and using fluorescence detection (lambda ex = 365 nm, lambda em = 750 nm). For recovery studies, isoBOSINC was added to muscles at levels of 0.067 and 0.67 micrograms/g; the mean recoveries were 100%, with coefficients of variation of 6.1 and 6.4%, respectively. For liver samples, the amounts added were 0.67 and 6.7 micrograms/g and for serum 0.67 and 6.70 micrograms/ml. The mean recoveries for liver were 86 and 93%, with coefficients of variation of 7.7 and 4.4%, respectively. For serum, the mean recoveries were 99 and 96%, with coefficients of variation of 2.6 and 6.9%, respectively. Due to its low detection limit and selectivity, the method is appropriate for pharmacokinetic as well as tumor uptake studies following in vivo exposure to isoBOSINC. Preliminary data on tissue distribution of the photosensitizer in normal rats are also presented.

An important factor in determining the efficacy of photosensitizing compounds in photodynamic therapy of tumors is the level to which tumors take up the photosensitizers after systemic injection. This parameter seems to be related to the transport modalities of the photosensitizer in the bloodstream. In this work the photosensitizer Zn(II)-tetradibenzobarrelenooctabutoxyphthalocyanine was shown to have an unprecedentedly high association with low-density lipoproteins (71% of the phthalocyanine in the plasma) when delivered in Cremophor micelles to tumor-bearing mice. This was accompanied by a particularly high tumor uptake at 24 h post-injection.

Four silicon phthalocyanine photosensitizers have been prepared and studied in an effort to learn more about the structural features that a silicon phthalocyanine must have in order to be a good photodynamic therapy (PDT) photosensitizer. The compounds that have been studied are the known phthalocyanines HOSiPcOSi(CH3)2-(CH2)3N(CH3)2, Pc 4; and SiPc[OSi(CH3)2(CH2)3N(CH3)2]2, Pc 12; and the new photosensitizers HOSiPcOSi(CH3)2- (CH2)3N(CH2CH3)(CH2)2N(CH3)2, Pc 10; and SiPc[OSi (CH3)2(CH2)3N(CH2CH3)(CH2)2N(CH3)2]2, Pc 18. The triplet lifetimes of the four photosensitizers, their singlet oxygen quantum yields, their ability to photoenhance the generation of lipid peroxidation products in human erythrocyte ghosts, their ability to partition into V79 cells and their ability to photokill V79 and L5178Y-R cells have been determined. It is concluded that the presence of a small axial ligand (e.g. an OH ligand) is not necessary for efficient photosensitization, the presence of two aminosiloxy ligands generally provides at least as good photosensitization as one such ligand, and the presence of an elongated diaminosiloxy axial ligand rather than a short aminosiloxy ligand is less desirable. Further, it is concluded that the presence of structural features leading to improvement in the association between the photosensitizers and important cellular targets are more useful than those leading to improvements in their already acceptable photophysical and photochemical properties.

Photodynamic therapy of neoplastic tissues is a new treatment modality that combines the in- vivo administration of a photosensitizer followed by its excitation with visible light, which leads to a photochemical reaction and tissue destruction. Naphthalocyanine derivatives are a class of second-generation photosensitizers that have excellent prospects as photodynamic therapeutic agents. Relevant to these types of applications are their photochemical properties, their tumor-localizing abilities, and their ability to elicit photodynamic responses. Bis(di- isobutyloctadecylsiloxy)silicon 2,3-naphthalocyanine (isoBOSINC) illustrates some of the above promising photoproperties: absorption in the red at 776 nm with an extinction coefficient greater than 105 M-1 cm-1, a triplet state lifetime of 331 microseconds and singlet oxygen yields of approximately 0.20. Due to their high degree of hydrophobicity, metallonaphthalocyanines require a variety of approaches before they can be administered to cells in vitro or injected in vivo. One approach is the selection of solubilizing agents or vehicles such as a solution of Tween 80 in saline or emulsions of Cremophor EL in saline. This paper describes studies in (a) drug uptake by tumors and other tissues as a function of isoBOSINC's dose; (b) drug levels in normal versus tumor-bearing rats; (c) in-vitro photostability of isoBOSINC; (d) effects of delivery systems on photosensitizer tissue levels and pharmacokinetics, and PDT outcome.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The possibility of extending photodynamic therapy to the treatment of highly pigmented neoplastic lesions was tested by using Si(IV)-naphthalocyanine (SiNc) as a tumor-localizing agent. Si(IV)-naphthalocyanine displays intense absorbance at 776 nm (epsilon = 5 x 10(5) M-1 cm-1), where melanin absorption becomes weaker. As an experimental model we selected B16 pigmented melanoma subcutaneously transplanted to C57BL mice. Upon injection of 0.5 or 1 mg kg-1 of liposome-incorporated SiNc, maximal accumulation of the photosensitizer in the tumor was observed at 24 h with recoveries of 0.35 and 0.57 microgram g-1, respectively. However, the tumor targeting by SiNc shows essentially no selectivity, since the photosensitizer concentrations in the skin (peritumoral tissue) were very similar to those found in the tumor at all postinjection times examined by us. Irradiation of SiNc-loaded melanoma with 776 nm light from a diode laser at 24 h postinjection induces tumor necrosis and delay of tumor growth. The effect appears to be of purely photochemical nature at dose rates up to 260 mW cm-2; at higher dose rates, thermal effects are likely to become important.

Mechanisms of cell death have been explored in cells and tumors treated with photodynamic therapy (PDT). Photosensitizers used for these studies were Photofrin, tetrasulfonated and nonsulfonated aluminum phthalocyanine, and a new silicon phthalocyanine [SiPc(OH)OSi(CH3)2(CH2)3N(CH3)2], referred to as PcIV. In mouse lymphoma L5178Y cells, a dose of PDT sensitized by PcIV which causes a 90% loss of cell survival induces apoptosis (programmed cell death) over a several-hour time course, beginning within 10 minutes of irradiation. Apoptosis is a metabolic process initiated by PDT-induced damage to membranes and triggered by the activation of phospholipases A2 and C and the release of Ca++ from intracellular stores. An endogenous endonuclease is activated and cleaves nuclear DNA in the internucleosomal region of chromatin. Subsequent metabolic events now appear to cause the loss of cellular NAD and ATP, the former a result of the activation of a second nuclear enzyme, poly(ADP-ribose) polymerase, by the endonucleolytically generated DNA strand breaks. Loss of ATP follows upon the loss of NAD needed for energy metabolism. Although the induction of apoptosis is efficiently produced by direct PDT damage to L5178Y cells, we now find that apoptosis is also produced by treatment of certain other lymphoid-derived cells and cells of epithelial origin. Under the limited set of conditions tested, there was no evidence for PDT-induced apoptosis in a fibroblast cell line, in mouse fibrosarcoma RIF-1 and L929 cells, in human adenocarcinoma A549 cells, or in human squamous cell carcinoma cells in culture. The evidence suggests that apoptosis, a form of metabolic cell death, is an important mechanism of tumor ablation in PDT-treated tumors, and that the induction of apoptosis may involve the interaction of direct PDT damage to malignant cells with factors produced by PDT action on vascular and other host cells.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Six new aluminum and silicon phthalocyanines have been synthesized and their photocytotoxicity toward V79 cells has been studied. The compounds that have been prepared are: A1PcOSi(CH3)2(CH2)3N(CH3)2, I; A1Pc-OSi(CH3)2(CH2)3N(CH3)3+I-, II; CH3SiPcOSi(CH3)2(CH2)3N(CH3)2, III; HOSiPcOSi(CH3)2(CH2)3N(CH3)2, IV; HOSiPcOSi(CH3)2(CH2)3N(CH3)3+I-, V; and SiPc[OSi(CH3)2(CH2)3N(CH3)3+I-]2, VI. Relative growth delay values for compounds I-VI and relative cytotoxicity values for compounds I, II, IV, V and VI have been determined. Compounds I and II have been shown to be comparable in photocytotoxicity to what is presumed to be A1PcOH.xH2O, and compound IV has been shown to have greater activity. The classes of compounds to which these six compounds belong appear to have potential for photodynamic therapy.

A water-soluble derivative of the highly hydrophobic molecule Si(IV)-naphthalocyanine was synthesized by the addition of two polyethyleneglycol ligands in axial positions to the centrally coordinated Si(IV) ion. The compound can be intravenously injected in homogeneous aqueous solution, where it is largely aggregated and remains mostly in an unbound state. While the naphthalocyanine is accumulated in significant amounts by an intramuscularly transplanted MS-2 fibrosarcoma in Balb/c mice, the dye shows little tumour selectivity and essentially no phototherapeutic activity. The situation is not improved by association of the naphthalocyanine with dipalmitoyl-phosphatidylcholine liposomes, probably owing to a lack of incorporation of the bulky dye molecule into the phospholipid bilayer.

A series of silicon and aluminum phthalocyanines is being investigated in this laboratory for their potential as photosensitizers for photodynamic tumor therapy (PDT). Of these, one of the silicon phthalocyanines [SiPc(OH)OSi(CH3)2(CH2)3N(CH3)2] (Pc IV) has proven to be highly efficient in a series of in vitro assays and in PDT in vivo. When compared to sulfonated or non-sulfonated aluminum phthalocyanine and/or Photofrin II, Pc IV produced greater effects at lower concentrations in a clonogenic assay with V79 cells, and in photoenhancement of lipid peroxidation in human erythrocyte membranes. Physiological responses of treated cells in vitro appeared similar to those produced by PDT with other sensitizers; however, the responses, such as the induction of apoptosis in murine lymphoma, occurred with greater efficiency when Pc IV served as photosensitizer. In order to evaluate the efficacy of Pc IV in vivo, the dye was suspended in corn oil or incorporated into liposomes and injected intraperitoneally into C3H mice bearing RIF-1 tumors. Pharmacokinetic studies showed efficient uptake of Pc IV into the tumor, as well as into liver and kidney. For PDT, tumors were irradiated with 675 nm light from an argon-pumped dye laser. Treatment of tumors up to 100 mm3 with 1.0 mg/kg Pc IV and 135 J/cm2 produced ablation of the tumor within 48 hours. Tumors > 200 mm3 could be ablated with 2.0 mg/kg Pc IV. The data suggest that Pc IV may be a highly efficient photosensitizer for tumor PDT.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The synthesis and characterization of a tetradibenzobarrelenoocta-n-butoxyzinc phthalocyanine, as well as the phthalocyanines t-butyldimethylsiloxy-N(3(beta) -acetoxy-23, 24-dinor-5-cholenoyl)-4-amino-n-butyldimethylsiloxysilicon phthalocyanine and bis- N(3(beta) -acetoxy-23,24-dinor-5-cholenoyl)-4-amino-n-butyldimethylsiloxysilicon phthalocyanine are reported. The zinc phthalocyanine is soluble, open at its center and highly hindered. It has a deep red absorption and a long triplet state lifetime. The silicon phthalocyanines have red absorptions and ligands bearing functions that have a resemblance to a part of the core of the low density lipoprotein fraction of blood serum. The zinc phthalocyanine has the potential to be a good photosensitizer, and the silicon phthalocyanines or related compounds have the potential to be preferentially accumulated by tumor cells. All three compounds are of interest for photodynamic therapy studies.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Using the direct measurement of the photosensitized luminescence of singlet molecular oxygen (1O2) the rate constants (kq) have been determined for 1O2 quenching by the monomeric molecules of the following phthalocyanines and naphthalocyanines in chloroform: tetra-(4-tert-butyl) phthalocyanine (I); octa-(3,6-butoxy) phthalocyanine (II), tetra-(6-tert-butyl)-2,3 naphthalocyanine (III), aluminium tetra-(1-tert-phenyl)-2,3 naphthalocyanine (IV), tri-(n-hexyl-siloxy) derivatives of silicon- (V), tin- (VI), aluminium- (VII) and gallium- (VIII) 2,3 naphthalocyanine. The following kq values were obtained (kq x 10(-8) M-1 s-1): 2.9 (I), 59 (II), 100 (III), 20 (IV), 3.9 (V), 53 (VI), 33 (VII), 110 (VIII). As most of the quenchers have the low-lying triplet levels, a contribution of the quenching mechanism based on the energy transfer from 1O2 to these levels has been analysed. A formula is proposed describing the relation between kq values caused by this mechanism, and photophysical constants of the quencher triplet state. This formula was applied to phthalocyanines, naphthalocyanines, beta-carotene and bacterochlorophyll a. The data suggest that the energy transfer can fully explain the activity of V and strongly contributes into the activities of II, III and VI-VIII. A charge transfer interaction might be an additional mechanism involved in 1O2 quenching by compounds studied. As some phthalocyanines and naphthalocyanines are strong physical quenchers of singlet oxygen they can be used as efficient inhibitors for photodestructive processes in photochemical systems.

Methods for the preparation of three siloxysilicon naphthalocyanines, a siloxygermanium tetraphenoxynaphthalocyanine, a siloxysilicon tetra-t-butyl-naphthalocyanine, a cofacial double-ring siloxysilicon naphthalocyanine, and a cofacial triple-ring siloxysilicon naphthalocyanine that are relevant to the search for second generation PDT sensitizers are outlined. Ultraviolet-visible spectra, NMR spectra, and other properties of these compounds are given and discussed. In addition, an attempt to make an aluminum tetradibenzobarreleno-naphthalocyanine is described.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Methods for the preparation of the naphthalocyanines SiNc(OSi(n-C6H13)3)2, SiNc(OSi(i-C4H9)2n-C18H37)2, GeNc(OSi(n-C6H13)3)2, SnNc(OSi(n-C6H13)3)2, AlNcOSi(n-C6H13)3 ' and GaNcOSi(n-C6H13)3 the halonaphthalocyanine isomer mixtures SiMc(Cl)4(OSi(n-C6H13)3)2 and SiNc(Br)4(OSi(n-C6H13)3)2; and the butoxyphthalocyanines GePc(0-n-C4H9)g(OSi(C2H5)3)2 , SnPc(O-n-C4H9)8(OSi(C2H5)3)2, Al(O-n- C4H9)8OSi(C2H5)3 , Ga(O-n-C4H9)8OSi(C2H5)3 , PdPc(O-n-C4H9)8, and Ru(O-n- C4H9)8(C6H5N)2 are outlined. Ultraviolet-visible spectra and other properties of these compounds are described, and their potential as sensitizers is touched upon.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Triplet-state properties of 1,4,8,11,15,18,22,25-octa-n-butoxyphthalocyanine and its zinc derivative were determined for the first time. The T1 state of the metal-free phthalocyanine was characterized by a short lifetime (tau T = 17 microseconds) and low quantum yield (phi T = 0.095), and quenching of the triplet by O2 occurred with a bimolecular rate constant (kT sigma = 1.3 x 10(8) M-1 s-1) that is indicative of an endogonic reaction. The zinc complex (ZnPc(OBu)8) was markedly better as a triplet photosensitizer with respect to both tau T (60 microseconds) and phi T (0.5). Quenching by O2 produced singlet oxygen with nearly 100% efficiency, and kT sigma (1.7 x 10(9) M-1s-1) was close to the spin-statistical diffusion-controlled limit. Phosphorescence measurements showed the energy of the T1 state of ZnPc(OBu)8 to be 100 kJ/mol, which is 6 kJ/mol above the 1 delta g state of O2. These photoproperties, together with Q-band absorption maxima in the mid-700 nm range indicate that metal-centered 1,4,8,11,15,18,22,25-octaalkoxyphthalocyanines have excellent potential as sensitizers in photodynamic therapy.