Intersystem Crossing Pathway in Quinoline鈥揚yrazole Isomerism: A Time-Dependent Density Functional Theory Study on Excited-State Intramolecular Proton Transfer

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• 作者：Yu-Hui Liu ; Sheng-Cheng Lan ; Chaoyuan Zhu ; Sheng-Hsien Lin
• 刊名：Journal of Physical Chemistry A
• 出版年：2015
• 出版时间：June 18, 2015
• 年：2015
• 卷：119
• 期：24
• 页码：6269-6274
• 全文大小：316K
• ISSN：1520-5215

文摘

The dynamics of the excited-state intramolecular proton-transfer (ESIPT) reaction of quinoline鈥損yrazole (QP) isomers, designated as QP-I and QP-II, has been investigated by means of time-dependent density functional theory (TDDFT). A lower barrier has been found in the potential energy curve for the lowest singlet excited state (S₁) along the proton-transfer coordinate of QP-II compared with that of QP-I; however, this is at variance with a recent experimental report [J. Phys. Chem. A 2010, 114, 7886鈥?891], in which the authors proposed that the ESIPT reaction would only proceed in QP-I due to the absence of a PT emission for QP-II. Therefore, several deactivating pathways have been investigated to determine whether fluorescence quenching occurs in the PT form of QP-II (PT-II). The S₁ state of PT-II has n蟺* character, which is a well-known dark state. Moreover, the energy gap between the S₁ and T₂ states is only 0.29 eV, implying that an intersystem crossing (ISC) process would occur rapidly following the ESIPT reaction. Therefore, it is demonstrated that the ESIPT could successfully proceed in QP-II and that the PT emission would be quenched by the ISC process.