TDDFT investigation on electronically excited-state hydrogen-bonding properties and ESIPT mechanism for the 2-(1H-imidaz
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ORIGINAL RESEARCH
TDDFT investigation on electronically excited-state hydrogen-bonding properties and ESIPT mechanism for the 2-(1H-imidazol-2-yl)-phenol compound Guang Yang 1 & Kaifeng Chen 1 & Gang Wang 1 & Dapeng Yang 2 Received: 22 June 2020 / Accepted: 22 September 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract In this work, DFT and TDDFT approaches have been executed to make a detailed exploration about the excited state luminescent properties as well as excited state intramolecular proton transfer (ESIPT) mechanism for the novel 2-(1H-imidazol-2-yl)-phenol (PI) compound. Optimized geometrical parameters of primary chemical bonds and infrared (IR) spectra prove that the O37H38···N26 hydrogen bond of PI should be strengthened in the S1 state. Insights into frontier molecular orbitals (MOs), we infer charge redistribution and charge transfer (ICT) phenomena motivate ESIPT trend. Via probing into potential energy curves (PECs) in related electronic states, we come up with the ultrafast ESIPT behavior due to low potential barrier. Furthermore, we search the reaction transition state (TS) and simulate intrinsic reaction coordinate (IRC) path; the ultrafast ESIPT behavior and mechanism of PI compound can be re-confirmed. We sincerely wish that this work could play roles in further developing novel applications based on PI compound and in promoting new ratiometric fluorescence probes in the future. Keywords Intramolecular hydrogen bond . Frontier molecular orbital . Excited-state proton transfer . Charge redistribution . Intrinsic reaction coordinate
Introduction As a typical weak interaction, hydrogen bond undoubtedly plays momentous roles in various photochemical and photophysical behaviors in nature [1–3]. As is known to all, explorations on excited state intramolecular proton transfer (ESIPT) reaction along with pre-existing hydrogen bond have become the hotspot in photochemical and photo-biological domains [4–10]. While generally, molecules or systems with ESIPT properties could exhibit dual fluorescence peaks under Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11224-020-01648-z) contains supplementary material, which is available to authorized users. * Guang Yang [email protected] 1
Basic Teaching Department, Jiaozuo University, Jiaozuo 454000, People’s Republic of China
2
State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, People’s Republic of China
specific photo-excitation. One fluorescence peak could be resulted from initial molecular structure prior to ESIPT behavior (i.e., enol configuration), and the other one derives from the form after ESIPT reaction (i.e., keto structure) [4–10]. Via comparing with the emission peak of the former, it can be found that the fluorescence of the latter one shows obvious red shift. On account of this kind of characteristics, practical applications could be expired such as light emitting diodes, fluores
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