Effect of Two Electron-Donating Substituents on Photochromism of Aryl Fulgide, 2-(2,6-Dimethyl-3,5-substituted benzylidene)-3-isopropylidenesuccinic Anhydride

Two electron-donating substituents (e.g. p-diethylaminostyryl) were introduced to an aryl structure of fulgide and photochromic performance was investigated. It was found that the strong electron-donating ability of the substituents caused a significant red shift of the colored form to the near-infrared region (λmax; 633 nm), resulting in a high molecular extinction coefficient (εmax; 24300 mol−1 cm−1). Furthermore, rapid reactions of both coloration and discoloration were observed; the quantum yields (φEC and φCE) were 0.65 and 0.052, respectively.