A series of diarylethenes derivatives with benzimidazole rings have been synthesized to examine a substituent effect on photochromic and photophysical properties. We examined the photochromic properties of the BTBI derivatives in several solvents. We found that the photochromic BTBI derivatives showed reversibly changing their absorption spectra upon UV and visible light irradiation. We also characterized the photochromic conversion yield, cyclization quantum yield (quantum yield for the open to closed-ring isomer), cyclo-reversion quantum yield (quantum yield for the close to open-ring isomer), and fluorescence quantum yield. The yield for the cyclization of the BTBI derivatives were low except for BTDBI (2-(4,5-bis(2-methylbenzo[b]thiophene-3-yl)thiophen-2-yl-1,3-dimethyl-1H-benzo[d]imidazole-3-ium iodide), which contains charged substituent in the benzimidazole ring. BTDBI also shows significant fluorescence stokes shifts compared with other BTBI derivatives. We also found that the cyclo-reversion reaction occurred upon the addition of metal ions. The results indicate that the oxidation of BTBI derivatives resulted in the ring-opening reaction. We can design suitable photochromic compounds based on these observations by introducing a benzimidazole ring to the photochromic diarylethene system.

Synthesis and characterization of photochromic diarylethene derivatives with benzimidazole ring

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