Photochromism of new unsymmetrical diarylethene derivatives bearing both benzofuran and thiophene moieties

A new class of unsymmetrical photochromic diarylethenes bearing both benzofuran and thiophene moieties was synthesized and the effects of substitution on their properties were discussed systematically. Two compounds among them show distinctly different conformation in the single crystalline phase: one crystallizes with an anti-parallel conformation which exhibit good photochromism, whereas the other crystallizes with a parallel conformation which exhibits no photochromism in the crystalline phase. Each of the compounds exhibited remarkable photochromism and functioned as a fluorescent switch in both solution and PMMA films. The electron-donating groups significantly increased the cyclization quantum yield, depressed the cycloreversion quantum yield, shifted the emission peak to a longer wavelength, and decreased the emission intensity; while the electron-withdrawing groups functioned as an inverse action for these diarylethene derivatives. The cyclic voltammograms results revealed that these diarylethenes exhibited evident electrochromism during electrolysis and the oxidative cyclization is thermodynamically. A new class of diarylethenes bearing both benzofuran and thiophene moieties was synthesized and substituent effects on their optical and electrochemical properties were studied systematically. [Display omitted] ► A new class of unsymmetrical diarylethenes was synthesized. ► The effects of substitution on their properties were studied systematically. ► They showed evident electrochromism during electrolysis.