Synthesis and Photochromic Properties of 3,3′-Dihydroxy-6,6′(or 7,7′)-Dimethyl-3,3′-Dipropyl-[2,2′-bi-1H-indenylidene]-1,1′-Dione

Abstract

3,3′-Dihydroxy-6,6′(or 7,7′)-dimethyl-3,3′-dipropyl-[2,2′-bi-1H-indenylidene]-1,1′-dione was found to undergo photochromism in a single crystalline phase from yellow to red. The structure of the compound was confirmed by X-ray crystallography analysis. Results showed that the compound contains a pair of isomers, 3,3′-dihydroxy-6,6′-dimethyl-3,3′-dipropyl-[2,2′-bi-1H-indenylidene]-1,1′-dione and 3,3′-dihydroxy-7,7′-dimethyl-3,3′-dipropyl-[2,2′-bi-1H-indenylidene]-1,1′-dione. A plausible reaction mechanism was proposed.