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Three symmetrical dithienylethenes bearing two electron-withdrawing aldehyde groups have been synthesized. And their structures were confirmed by 1H NMR, 13C NMR and HRMS (ESI). Investigation on photochromic properties indicated that they had good photochromic behavior with excellent fatigue resistance upon irradiation with UV or visible light. And it was found that the aldehyde substituent position had a significant effect on their photochromic properties. The DFT calculations further validated those experimental results for their photochromic behavior. Furthermore, they may be used as versatile building blocks to construct novel photochromic materials. [ABSTRACT FROM AUTHOR]

A series of symmetrical imidazole- and N-methylated imidazole-based diarylethenes were synthesized, and the structures have been well characterized by NMR spectroscopy and mass spectrometry. Their photochromism were investigated upon UV/vis light irradiation in DMF solution. A significant red-shift of UV absorption was observed after irradiation with UV light when substituents on the benzene ring (such as methoxyl group) were introduced. But N-methylation on the two imidazole rings will result in a blue-shift of UV absorption. The photophysical properties can be adjusted by changing the substituents, which provides a new strategy for the design of diarylethenes with excellent properties. [ABSTRACT FROM AUTHOR]

Abstract: A novel series of diarylethenes incorporating different heterocycles and their N-methylated derivatives have been synthesized, and the products have been characterized by means of NMR, MS and elemental analysis. Each of the compounds displays photochromism and “turn-on” fluorescence properties upon irradiation with UV light. It has been found that both the nature of the heterocycle attached to the imidazole ring and methylation of the imidazole ring greatly affect the optical properties. The light-emitting properties can be easily tuned from blue light-emitting to yellow light-emitting fluorescence by varying the nature of the heterocycle or by simple modification of structures, which provides a new strategy for the design of novel fluorescent switches. Moreover, Cu2+, Hg2+, and Fe3+ greatly affect the fluorescence properties of diarylethene 4 in the photostationary state, so that these systems might be deployed in a novel molecular sensor for the detection of such cations by fluorescence recognition. [Copyright &y& Elsevier]