Sensitizers phthalocyanines

Gu C., Sun L., Zhang T., Li T., and Zhang X., High-sensitivity phthalocyanine LB film gas sensor based on field effect transistors. Thin Solid Films, 327-329, 383-386, 1998. 

Given stringent requirements for effective sensitizers and the desire to use wavelengths further to the red for therapeutic appHcations, definition of newer sensitizers has been a principal area of research since about 1987. Expanded theoretical and experimental understanding of photophysics has been a key element in identifying new classes of potential sensitizers (93—98). Research has focused on cationic derivatives of Nile Blue (93), metaHo-phthalocyanines (94), naphthalocyanines (95), chlorin-type compounds (96), expanded ring porphyrinoids (97), as well as porphyrins other than hematoporphyrin and its derivatives (98). This work has also been reviewed (10,91). Instmmentation for photodynamic therapy has been reviewed (99). 

Phthalocyanines have been used to incorporate semiconductor properties in polymers (182) or to develop a thin-film transistor (183). Phthalocyanines and their derivatives can act as dyes in color photography (qv) (184) or electrophotography (185). Light-sensitive compositions for use on Hthographic plates are comprised in part of copper phthalocyanine blue (186). Dichlorosilicon phthalocyanine [19333-10-9] has been used in the... 

Chemical and biological sensors (qv) are important appHcations of LB films. In field-effect devices, the tunneling current is a function of the dielectric constant of the organic film (85—90). For example, NO2, an electron acceptor, has been detected by a phthalocyanine (or a porphyrin) LB film. The mechanism of the reaction is a partial oxidation that introduces charge carriers into the film, thus changing its band gap and as a result, its dc-conductivity. Field-effect devices are very sensitive, but not selective. 

Naphthalocyanins, phthalocyanins, and porphyrins as sensitizers in photodynamic cancer therapy 98IZV836. 

Porphyrins, modified natural chlorophylls, chlorins, phthalocyanins, xanthenes, phenothiazine, and phenoxazine dyes as new sensitizers for photodynamic therapy 98MI50, 98MI51, 98MI52, 98MI53. 

Disodium phthalocyanine (PcNa2) can be prepared in the same way as the dilithium compound by reacting sodium pentoxide in pentan-l-ol with phthalonitrile. It is more sensitive towards moisture and even alcohol than the dilithium phthalocyanine and is readily demeta-lated.58... 

Organic dyes, aside from their role as sensitization agents for wide band gap semiconductors have been employed also for stabilization of narrow band gap semiconductors. The majority of such studies have considered metal or metal-free phthalocyanine films for both sensitization and electrode protection purposes [35]. 

Diaz AF, Logan JA(1980)Electroactive polyanihne films. JElectroanalChem 111 111-114 Noufi R, Nozik AJ, White J, Warren LF (1982) Enhanced stability of photoelectrodes with electrogenerated polyanUine films. J Electrochem Soc 129 2261-2265 Noufi R, Tench D, Warren LE (1981) Protection of semiconductor photoanodes with photoelectrochemicaUy generated polypyrrole films. J Electrochem Soc 128 2596-2599 Jaeger CD, Fan FRF, Bard AJ (1980) Semiconductor electrodes. 26. Spectral sensitization of semiconductors with phthalocyanine. J Am Chem Soc 102 2592-2598 Gerischer H (1977) On the stability of semiconductor electrodes against photodecomposition. J Electroanal Chem 82 133-143... 

Figure 12 Photocurrent action spectra of nanocrystalline Ti02 films sensitized by fe(3,4-dicarboxypyridine) Ru11 (1,4,8,11,15,18,22,25-octamethyl-phthalocyanin) (54). The incident photon to current conversion...

The photophysical properties of magnesium(II) tetra-(i-butyl)phthalocyanine (27) have been studied in solution, in micelles and in liposomes cation radical formation (CBr4 as electron acceptor) has been detected with UV excitation, or by a two-photon excitation using a pulsed laser in the therapeutic window at 670 nm.118 The Mg11 complex of octa(tri-z -propylsilylethy-nyl)tetra[6,7]quinoxalinoporphyrazine (28) has been prepared as a potential PDT sensitizer. The synthesis is shown in Figure 8. Compound (28) has Amax 770 nm (e = 512,000 M-1 cm-1), d>f = 0.46 and d>A = 0.19 (all in THF, under air).119... 

The palladium(II) phthalocyanines are satisfactory singlet oxygen generators. Thus, f>A values for tetra-t-butylphthalocyanine ((27), with stated replacement for Mg) are 2H, 0.22 Zn, 0.34 Pd, 0.54, i.e., increasing in line with the heavy atom effect.180 For palladium(II) tetra-t-butylphthalocyanine ((27), Pd instead of Mg) in benzene at 290 K, 4>f= 0.048 and X = 0.49.180 However, palladium(II) 2,3-dihydroxy-9,16,23-tri-t-butylphthalocyanine was synthesized by a mixed condensation (1 9 mix of appropriate dinitriles) as a likely amphiphilic sensitizer, but did not show bioactivity in an enzyme assay, possibly because of aggregation.180... 

The photodynamic effect of chloroaluminum(III) phthalocyanine ((47), with C1A1 in place of Zn), a commercial product, was reported by Ben-Hur and Rosenthal.302 The photosensitizer was delivered in ethanol to cultures of Chinese hamster fibroblasts. After equilibration (16 h), exposure to visible light (fluence rate 64 Wm-2) of a suspension in PBS for 2 min gave a 3 log kill. Lack of water solubility is a problem, and for in vivo PDT of EMT-6 mammary tumors in mice a Cremophor emulsion was employed.303 The compound was a more effective PDT sensitizer than... 

As a result of their low redox potentials [173], bis(phthalocyaninato) lanthanide complexes are often inadvertently reduced or oxidized, and they are also very sensitive to acids and bases. In order to solve these problems, Veciana et al. achieved certain success on designing a series of novel compounds with characteristics that would give them improved redox stability. Electroactive ligands based on phthalo-cyaninato tetra dicarboximide [175] or perfluorinated phthalocyanine [176] were used to assemble the double-decker lanthanide complexes, with the effect of stabilizing the negative charge of the anionic state of the compounds, which resulted in a strong shift of 0.7 V of their first oxidation potentials. 

---