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.

Two novel isomeric photochromic diarylethenes with an indene bridging unit have been prepared by a simple and efficient one-step synthesis method. Their properties, including photochromic behavior, fluorescent properties and fatigue resistance, have been investigated. These two isomeric compounds showed photochromic back-and-forth reactions with ultraviolet and visible light both in solution and in PMMA film. Their ring-open forms exhibited appreciable fluorescence, which was quenched by the ring-closed forms. All results indicated that diarylethenes derivatives with indene-aryl bridges exhibited rather high fatigue resistance and good thermally irreversible photochromic properties.