Effects of substitution on the optoelectronic properties of photochromic diarylethenes bearing a pyrrole moiety

摘要

Five diarylethenes bearing a pyrrole moiety were synthesized in order to investigate the effects of the substituents on the properties of these compounds. The structures of three of the diarylethenes were determined by single-crystal X-ray diffraction analysis. All of the diarylethene derivatives exhibited notable photochromism and functioned as effective fluorescent photo-switches in solution and in poly (methyl methacrylate) films. The absorption maxima and the quantum yields of cyclization and cyclo-reversion increased whereas the emission peaks and the emission intensities decreased evidently when the electron-withdrawing/donating substituent was attached at the para-position on the terminal benzene ring. Cyclic voltammograms indicated that the electron-withdrawtng/donating substituents decreased the bang gaps of the open-ring isomers but enhanced those of the closed-ring isomers, compared with the unsubstituted parent diarylethene. The properties of these diarylethene derivatives were significantly different from each other, which might be attributed to the different substituent effects.