New photochromic symmetrical and unsymmetrical bis(heteroaryl)maleimides: A spectrokinetic study |
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Authors: | M Cipolloni F Ortica A El Yahyaoui A Heynderickx C Moustrou G Favaro |
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Institution: | 1. Università di Perugia, Dipartimento di Chimica, Via Elce di Sotto 8, 06123 Perugia, Italy;2. Université de la Méditerranée, Faculté des Sciences de Luminy, UMR CNRS 6114, 13288 Marseille Cedex 9, France |
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Abstract: | The photochromic behavior of two newly synthesized diarylethenes is here presented. The compounds studied are the symmetrical (1-benzyl-3,4-bis(2-methylbenzob]thiophen-3-yl)-1H]-2,5-dihydropyrrol-2,5-dione) and the unsymmetrical (1-benzyl-3-(2-methylbenzob]thiophen-3-yl)-4-(2,5-dimethyl-3-thienyl)-1H]-2,5-dihydropyrrol-2,5-dione). Upon stimulation with UV or violet light, these compounds become red-colored due to photocyclization and cyclorevert to the light yellow open form upon irradiation with visible light. In this work, absorption and fluorescence spectra, molar absorption coefficients of the ethenic and cyclized forms, fluorescence quantum yields and photochemical quantum yields of both the forward and back photoreactions were determined. Temperature, excitation wavelength and solvent effects were explored. The symmetrical compound was found to be a bistable photochrome. In contrast, the unsymmetrical molecule resulted unsuitable as photochrome because of side degradation processes occurring in competition with cyclization. |
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Keywords: | Diarylethenes Photochromism Solvatochromism Absorption spectroscopy Fluorescence spectroscopy Laser flash photolysis Photoreaction quantum yields |
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