title: Excited-state intramolecular hydrogen bonding of compounds based on 2-(2-hydroxyphenyl)-1,3-benzoxazole in solution: a TDDFT study.
abstract: The excited-state properties of intramolecular hydrogen bonding in the compounds based on 2-(2-hydroxyphenyl)-1,3-benzoxazole (6 and its tautomers 6a and 6b) have been investigated using theoretical methods. According to the geometric optimization and IR spectra in the ground and excited states calculated by density functional theory (DFT) and time-dependent DFT (TD-DFT) methods respectively, the type of intramolecular hydrogen bonding N⋯HO in 6 and 6a is demonstrated to be significantly strengthened, while NH⋯O in the tautomers 6a and 6b are proved to be sharply weakened upon excitation to excited state S1. The calculated absorption peaks of 6 are in good accordance with the experimental results. Moreover, other compounds based on 6 that R1 and R2 are both substituted as well as that only R1 is substituted are investigated to understand the effect of substituent on intramolecular hydrogen bonding. It is found that the hydrogen bond strength can be controlled by the inductive field effect of the substituent. In addition, the intramolecular charge transfers (ICT) of the S1 state for 6 and its tautomers 6a and 6b were theoretically investigated by analyses of molecular orbital.
authors.affiliation: Department of Physics, Henan Normal University, Xinxiang 453007, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Physics, Henan Normal University, Xinxiang 453007, China. Electronic address: yf-liu@htu.cn.
authors.forename: Yufang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Physics, Henan Normal University, Xinxiang 453007, China.
authors.forename: Yonggang
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Physics Laboratory, North China University of Water Resources and Electric Power, Zhengzhou 450045, China.
authors.forename: Dapeng
authors.initials: D
authors.lastname: Yang
authors.affiliation: Department of Physics, Henan Normal University, Xinxiang 453007, China.
authors.forename: Jinfeng
authors.initials: J
authors.lastname: Sun
mesh_terms: D001583:Benzoxazoles / Q000737:chemistry*; D004583:Electrons; D006860:Hydrogen Bonding; D008958:Models, Molecular; D011789:Quantum Theory; D012996:Solutions; D013055:Spectrophotometry, Infrared
chemical_list: D001583:Benzoxazoles; D012996:Solutions
keywords: DFT/TD-DFT; Excited state; Hydrogen bonding dynamics; Spectral shift