Synthesis of novel diarylethene compounds containing two imidazole bridge units and tuning of their optical properties

A novel series of symmetrical diarylethenes incorporating two imidazole bridge units and their N-methylated derivatives have been synthesized, and the products have been characterized by means of NMR and MS. Each of the compounds displays excellent photochromism and both “turn-off” and “turn-on” fluorescence properties upon UV/vis light irradiation in solution. It has been found that the electronic properties of substituents on the benzene ring, methylation of the N–H units on the two imidazole rings and Cu2+ have great effects on both the photochromic property and fluorescence property of these diarylethenes. The photophysical properties of these compounds can be easily tuned by varying the electronic properties of the substituents or by simple modification of the molecular structure, which provides a new strategy for the design of novel fluorescent diarylethene systems to be used as switches.

Graphical abstractSeven symmetrical diarylethenes incorporating two imidazole bridge units have been synthesized. It has been demonstrated that both the electronic properties of the substituent on the benzene ring, methylation of the N−H units on the two imidazole rings and Cu2+ have great effects on the photochromic property and fluorescence property of these diarylethenes.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► A novel series of symmetrical diarylethenes incorporating two imidazole bridge units and their N-methylated derivatives have been synthesized. ► Each of the compounds displays excellent photochromism and both “turn-off” and “turn-on” fluorescence properties upon UV/vis light irradiation in solution. ► Cu2+ have great effects on both the photochromic property and fluorescence property of these diarylethenes.