An Optic/Proton Dual-Controlled Fluorescence Switch based on Novel Photochromic Bithienylethene Derivatives

A simple method for the synthesis of new bithienylethenes bearing a functional group on the cyclopentene moiety is developed. Three new photochromic compounds (4a, 4b, 4c) have been successfully synthesized through this simple method, and exhibit good photochromic properties with alternate irradiation of ultraviolet and visible light. Furthermore, the ?uorescence of compound 4a, which bears a quinoline unit on the cyclopentene, can be modulated via optic and proton dual inputs. Upon excitation by 320 nm light, 4a emits a strong ?uorescence at 404 nm. After irradiation with 254 nm light, the emission intensity is reduced due to the ?uorescence resonance energy transfers (FRET) from quinoline unit to bithienylethene unit. Moreover, on addition of H+, the fluorescence is quenched completely due to the protonation of the quinoline. In addition, both the FRET and protonation process are reversible, which indicates a potential application in molecular switches and logic gates.