金属酞菁敏化光还原硝基化合物的反应

本文研究了各种金属酞菁以及带有不同取代基的锌酞菁敏化光还原硝基化合物的反应。确定了光敏还原反应的主要产物是氨基和羟氨基化合物;羟氨基化合物与亚硝基化合物通过暗反应缩合生成偶氮N-氧化物。测定了它们的氧化还原电位和荧光量子产率。从敏化光还原反应的量子产率及荧光猝灭与硝基化合物浓度的依赖关系,计算出各种金属酞菁激发单重态与三重态的敏化效率。受激发金属酞菁将电子转移至硝基化合物是敏化光还原反应的起始过程。电子转移生成离子自由基对后,电荷分离与逆电子转移过程相互竞争。由于自旋选择规则的限制,激发三重态的敏化效率一般比激发单重态的敏化效率高。为了提高敏化光还原反应的效率,除选择三重态产率较高的敏化剂外,改变敏化剂的结构可提高敏化剂激发单重态的敏化效率,从而提高敏化光还原反应的量子产率.

Metal phthalocyanine-sensitized photoreduction of nitro-compound

Metal phthalocyanine-sensitized photoredn. of dimethyl-4-nitrophthalate by ascorbic acid was investigated. The primary photoreaction products are the corresponding amino- and hydroxylamino-compds. The azoxy-compd. is formed by coupling of the nitroso-compd. with hydroxylamino-compd. in the presence of air through secondary dark reaction. The redox potential and fluorescence quantum yield are also determine The variation of the quantum yield for the sensitized photoredn., the relative fluorescence quantum yield and their product with the concentration of nitro-compd. were examined The efficiency of photoredn. sensitized by the singlet and triplet excited states of metal phthalocyanine was calculated Electron transfer from the excited metal phthalocyanine to the nitro-compd. was a primary process in the sensitized photoredn. A necessary requirement for a good sensitizer is that the triplet state is populated in high yield. An alternative way is to design a suitable phthalocyanine skeleton to overcome geminate recombination of the ion pair in order to increase the efficiency of photoredn. sensitized by singlet-excited state of the sensitizer, so as to increase the quantum yield of the total sensitized photoredn.