Photochromism of Quinoid Compounds

The paper presents the results of studies on the photochromic transformation mechanisms for three classes of quinone derivatives. Photoisomerization of the para-quinone to the anaquinone due to photochemical migration of hydrogen, aryl, or acyl groups is common to these processes. The mechanism of photochromic transformations of 1-alkyl- and 1-acyloxyanthraquinones has been investigated in detail. The primary photochemical steps of these processes - the migrations of hydrogen or an acyl group - are adiabatic photochemical reactions at the triplet potential energy surface. Variation of substituents in the anthraquinone ring, in the alkyl group of 1-alkylanthraquinones, and particularly in the acyl group of 1-acyloxyanthraquinones makes it possible to change (from several microseconds to seconds) the lifetimes of coloured photoinduced products at room temperature.