PHOTOCHROMISM OF QUINOID COMPOUNDS

The paper presents the results of studies on the photochromic transfor mation mechanisms for three classes of quinone derivatives. Photoisome rization of the para-quinone to the ana-quinone due to photochemical m igration of hydrogen, aryl, or acyl groups is common to these processe s. The mechanism of photochromic transformations of 1-alkyl- and 1-acy loxyanthraquinones has been investigated in detail. The primary photoc hemical steps of these processes - the migrations of hydrogen or an ac yl group - are adiabatic photochemical reactions at the triplet potent ial energy surface. Variation of substituents in the anthraquinone rin g, in the alkyl group of 1-alkylanthraquinones, and particularly in th e acyl group of 1-acyloxyanthraquinones makes it possible to change (f rom several microseconds to seconds) the lifetimes of coloured photoin duced products at room temperature.