Mechanism of the photochr0mic conversions of 1-phenoxy-4-acetoxy-9,10-anthraquinone

Abstract

In an earlier paper [i] we have described the photochromic conversion of l-phenoxy-4acetoxy-9,10-anthraquinone(I) to 9-phenoxy-10-acetoxy-l,4-anthraquinone(II), which proceeds through the intermediate formation of a derivative of 1,10-anthraquinone, and it was established that during this conversion two successive migration processes occur: an initial photochemical migration of the phenyl group and a subsequent dark migration of the acety! group [i]. Recently [2, 3] we have discovered a photoinitiated, thermally reversible migration of the acetyl group for a number of derivatives of l-acetoxy-9,10-anthraquinone and 9-acetoxy-l,4-anthraquinone. From these results one can assume that for compounds I and II containing two different groups able to migrate under the action of light, besides the photoinitiated migration of the phenyl group, the possibility potentially exists of photoinitiated migration of the acetyl group. In the present work a detailed study has been made of the mechanism of the photochromic conversions of l-phenoxy-4-acetoxy-9,10-anthraquinone (utilizing the new data in [2, 3]), the nature of the intermediate products have been established and the values of the photochemical quantum yields and of the rate constants of the dark stages of the photochromic cycle have been determined.