Substituent and solvent effects on the fluorescent and photochromic properties of 2-(2-pyridyl)imidazole containing diarylethene derivatives

Abstract

Five diarylethene derivatives with 2-(2-pyridyl)imidazole as the ethene bridges (PI-BTEs) were synthesized and characterized. The structures and performances of the PI-BTEs (L1–L5) could be modified from not only the thiophene unit, but also the substituent on the imidazole nitrogen. Noteworthily, replacing the thiophene with the benzothiophene, the fatigue resistance is significantly improved, the centre absorption bands of the closed forms shift from 572 nm (L3) to 550 nm (L2), and the colours of the solutions change from pale pink in L3 to red-purple in L2. Additionally, the Stokes shift (Δν) values of L3 in various solvents display good linear relationships with the donor number (DN) of the solvents, and the solvent polarity parameter Δf.