Photochemical Reactions of Bromoanthraquinones in Ethanol at Room Temperature Studied by Steady-State Photolysis and Laser Photolysis

Article abstract of DOI:10.1246/bcsj.59.2735

Photolyses of α-bromoanthraquinones (1-bromo-, 1,5-dibromo- and 1,8-dibromoanthraquinones) with 366 nm light in ethanol at room temperature gave rise to the formation of debrominated 9,10-anthracenediol as a final product.This was interpreted in terms of the sequence of the formation of α-bromo-9,10-anthracenediols followed by the photochemical dehydrobromination yielding the corresponding anthraquinones with one less bromine atom than original ones.Photolysis of 2-bromoanthraquinone gave rise to the formation of 2-bromo-9,10-anthracenediol, and no dehydrobromination was observed.Combined with the values of the quantum yields of photoreduction, the results of the laser photolyses revealed that the rate constant for the hydrogen-atom abstraction from ethanol decreased as an increase of the ??^* character of the lowest triplet states of a α-bromoanthraquinones.