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α-Methyl and α-phenyl substituted 2 and 4-styrylpyridines were prepared by classical routes. The geometrical isomers were separated and characterized on the basis of their U.V. absorption spectra and/or of their behaviour under U.V. irradiation which led to photoisomerization and photocyclization products. The last photoreaction, in the case of α-phenyl derivatives, gave pyridyl-substituted phenanthrenes and phenyl-substituted azaphenanthrenes which were isolated and characterized. Spectral, chromatographic and physical properties of trans and cis derivatives and related photocyclization products are given as well as some kinetic data for the photochemical reactions. 相似文献
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Giulio Cauzzo Ciorgio Gennari Giulio Jori† § John D. Spikes‡ 《Photochemistry and photobiology》1977,25(4):389-395
Abstract— A kinetic investigation was performed on the photooxidation of methionine sensitized by various porphyrins at different oxygen concentrations. The rate of photooxidation was found to be strongly dependent on the nature of the sensitizer. In the case of hematoporphyrin, chelation of Mg2+ and Zn2+ and especially of Cu2+ and Fe2+ caused a significant decrease of the photosensitizing efficiency. Fluorescence and/or flash photolysis studies showed that such a decrease is ascribed to an enhancement of the non-radiative decay of the first excited singlet state as well as to a reduction of the triplet lifetime. The sensitizing efficiency is also dependent on the nature of the porphyrin side chains. A reaction mechanism involving 1 O2 as the oxidizing agent is proposed. 相似文献
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Abstract —Crystal violet sensitizes the selective photooxidation of cysteine to cysteic acid; hydrogen peroxide is also formed as an end product. The participation of singlet oxygen in the photoreaction has been ruled out, since exposure of cysteine to this reagent, generated by chemical or photochemical processes, gives only cystine as a product. The photoreaction is inhibited by radical scavengers such as hydroquinone and allylic alcohol. A mechanism is proposed involving hydrogen abstraction by the triplet dye from the thiol group of cysteine. 相似文献
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