Sythesis of a novel unsymmetrical photochromic diarylethene compound bearing indole unit

A novel unsymmetrical diarylethene derivative bearing both indole and thiophene moieties, in which 1,3-dithiolpentane group was substituted at the meta-positions of the terminal phenyl ring, was synthesized. At the same time, its photochromic properties and fluorescence switch were investigated in detail. The results showed that this compound exhibited reversible photochromism, undergoing reversible cyclization and cycloreversion reactions upon alternating irradiation with UV and visible light both in solution and in PMMA film, and its absorption maxima were observed at 584 nm in hexane and at 607 nm in PMMA amorphous film, respectively, upon irradiation with 297 nm UV light. The fluorescence intensity of diarylethene decreased dramatically along with the photochromism from open-ring isomer to closed-ring isomer upon irradiation with 297 nm UV light in PMMA. In hexane solution, the open-ring isomer of the diarylethene 1 exhibited relatively strong fluorescence at 426 nm when excited at 350 nm. This new photochromic system also exhibited remarkable optical storage character.