A novel strategy for estimation of selective photochromism by the fluorescence change in a multiswitchable dithienylethene system

Abstract

Dithienylethenes 1 and 2, consisting of three photochromic units linked by imidazole bridges, together with its N-methylated derivatives 3 and 4, have been synthesized. Their photochromic properties and fluorescence behaviors have also been investigated in solution by irradiation with various wavelengths of UV light. It was found that the dithienylethene 1 showed selective photochromism, indicated by the fluorescence change upon irradiation with 365 nm and 302 nm light. However, dithienylethenes 2, 3 and 4 only underwent a photocyclization reaction in the middle switchable unit under the same conditions. Moreover, for dithienylethenes 2 and 4, introduction of fluorine atoms on the cyclopentene evidently enhanced the photochromic properties compared with perhydro-substituted dithienylethenes 1 and 3. And dithienylethene 3 could act as one potential fluorescent molecular switch.