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Indexed by:期刊论文

Date of Publication:2014-04-01

Journal:CANADIAN JOURNAL OF CHEMISTRY

Included Journals:SCIE、EI、Scopus

Volume:92

Issue:4

Page Number:274-278

ISSN No.:0008-4042

Key Words:excited state intramolecular proton transfer (ESIPT); intramolecular charge transfer (ICT); fluorescence; time-dependent density functional theory (TDDFT); paeonol

Abstract:An excited-state intramolecular proton transfer (ESIPT) coupled charge transfer reaction of paeonol was investigated both experimentally and theoretically. The ESIPT reaction of paeonol was predicted based on the large Stokes shift, which is observed in steady-state absorption and fluorescence spectra in an ethanol solution. The steady-state spectra in some solutions, such as methanol, ethanol, propanol, dichloromethane, and n-hexane, illustrate that the ESIPT reaction of paeonol has no dependence on the solvent properties. Therefore, the excited-state intermolecular proton transfer cannot be generated in protic solvents. Using the density functional theory and time-dependent density functional theory methods, we make a subsequent theoretical calculation that indicates that the ESIPT reaction of paeonol occurs through the intramolecular hydrogen bond O-H center dot center dot center dot O=C. The excited-state potential energy curve of paeonol indicates that the ESIPT reaction is a barrierless process, and the fluorescence emission of paeonol at 493 nm in the ethanol solution was assigned to the keto isomer fluorescence. Additionally, we also found an intramolecular charge transfer in the excited state by analysing the frontier molecular orbitals of paeonol.