Importance of a low-lying n¦Ð^*-state in the photo-isomerisation reaction of Z-methylfurylfulgide

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• 作者：Jan Boyke Schö ; nborn ; Bernd Hartke ; ^{hartke@pctc.uni-kiel.de}
• 关键词：CASSCF ; CASPT2 ; Multi-reference ; Excited states ; Photoswitches
• 刊名：Journal of Photochemistry and Photobiology A: Chemistry
• 出版年：2013
• 出版时间：1 July, 2013
• 年：2013
• 卷：263
• 期：Complete
• 页码：34-40
• 全文大小：1468 K

文摘

Knowledge about the character of electronic states involved in ultrafast photoreactions is essential for understanding the dynamics leading to static and transient experimental spectra. Here we present a detailed study of the three lowest-energy electronic states of the photochromic switch methylfurylfulgide in its Z-form and of their changes as they approach the S₁S₀-conical intersection that facilitates the formation of E-methylfurylfulgide. We studied the molecular energy landscape by identifying important points along the reaction coordinate (Franck-Condon point, S₁-energy minimum and S₁S₀-conical intersection) by state-averaged CASSCF(10,9)/6-31g(d,p) calculations, assigned the character of the three lowest electronic states at these points and verified our classifications by CASPT2(18,13) calculations in a basis of polarised triple-zeta quality for the atoms relevant to the reaction and polarised double-zeta for the others. In contrast to the E¡úZ interconversion, it turns out that a proper active space for the Z¡úE interconversion should consist not only of ¦Ð orbitals but should contain also orbitals of n character. We expect this to experimentally manifest itself in visible differences between Z¡úE and E¡úZ behaviour.