Oxidation Oxygenation Photosensitized

Sortino et al. reported the use of light irradiation on SAMs supporting the anticancer drug flutamide to study its photoreactivity and product release of nitric oxide. The authors were able to conduct studies in the absence of noxious side effects such as singlet-oxygen photosensitization and observed that nitric oxide production halted when the light was turned off [103], Another photoactive molecule, azobenzene, has recently been exploited in the SAM community to aid in studies on cell adhesion and enzyme inhibition [104], Pearson and coworkers described the use of photoisomerizable SAMs of azobenzene to conduct a series of serine and cysteine protease inhibition experiments. When light of 340-380 nm is used, the... 

Thiazole is relatively resistant to oxidation. Under photosensitized oxygenation, triphenylthiazole affords various products of ring cleavage, depending on the sensitizer and the solvent employed (Scheme 17) (69BCJ2973). 

Murtinho, D., Pineiro, M., Pereira, M. et al. (2000). Novel Porphyrins and a Chlorine as Efficient Singlet Oxygen Photosensitizers for Photooxidation of Naphthols or Phenols to Quinones, J. Chem. Soc. Perkin Trans., 2, pp. 2441-2447 Sorokin, A. and Tuel, A. (1999). Heterogeneous Oxidation of Aromatic Compounds Catalyzed by Metallophthalocya-nine Functionalized Silicas, New J. Chem., 23, pp. 473-476 Sorokin, A., Mangematin, S. and Pergrale, C. (2002). Selective Oxidation of Aromatic Compounds with Dioxygen and Peroxides Catalyzed by Phthalocyanine Supported Catalysts, J. Mol. Catal. A Chem., 182-183, pp. 267-281. 

Photooxidafions are also iudustriaHy significant. A widely used treatment for removal of thiols from petroleum distillates is air iu the presence of sulfonated phthalocyanines (cobalt or vanadium complexes). Studies of this photoreaction (53) with the analogous ziuc phthalocyanine show a facile photooxidation of thiols, and the rate is enhanced further by cationic surfactants. For the perfume iudustry, rose oxide is produced iu low toimage quantifies by singlet oxygen oxidation of citroneUol (54). Rose bengal is the photosensitizer. 

Depending on the relative concentration of reactive substrate and dissolved molecular oxygen ( 02), RF is able to induce photosensitized oxidation of molecular targets by either Type I (electron-transfer) or Type II (energy-transfer) processes (Foote, 1991). In Type I... 

Foote, C., Photosensitized oxidation and singlet oxygen conseqnences in biological systems, in Free Radicals in Biology, Pryor, W.A., Ed., Academic Press, New York, 1976. 

Photochemical irradiation of dimethyl and diethyl sulphoxides yields the corresponding sulphone in the presence of air and a photosensitizer such as methylene blue in yields up to 99% . Sulphoxides are also oxidized when they act as traps for persulphoxides, the intermediate formed on reaction of a sulphide with photochemically generated singlet oxygen - , equation (9). Isotope studies have shown that such reactions proceed through a linear sulphurane intermediate . Persulphones also react with sulphoxides in a similar manner , equation (10). 

Moreover, carotenoids may quench electronically excited states and scavenge free radicals formed in the retina, and therefore protect biomolecules from oxidative damage. Due to the low energy level of the first excited triplet state ( Car), carotenoids (Car) can act as efficient acceptors of triplet state energy from photosensitizers (S) (Equation 15.1), such as all-tra .s-retinal, the photosensitizers of lipofuscin (Rozanowska et al., 1998), or singlet oxygen C02) (Equation 15.2) (Cantrell et al., 2003) ... 

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