Synthesis and properties of a novel photochromic diarylethene based on five and six rings

A new unsymmetrical photochromic diarylethene, 1-(2-cyanophenyl)-2-[2-methyl-5-(3-trifluoromethylphenyl)-3-thieny]perfluorocyclopentene (1a), was synthesized, and its photochromic properties were investigated. The compound exhibited good photochromism both in solution and in PMMA film with alternating irradiation by UV/VIS light. Upon irradiation with UV light, the colorless open-ring isomer 1a turned purple both in hexane and in PMMA film, and the maxima absorption of its closed-ring isomer 1b are 536 and 547 nm, respectively. The fluorescence intensity decreased along with the photochromism upon irradiation with 297 nm light and its closed-ring isomer showed weak fluorescence.