title: High-pressure Raman studies on aqueous protonated thiazole: presence of charge-enhanced C-H...O hydrogen bonds.
abstract: Close interactions of the charge-enhanced C-H...O type have been analyzed both experimentally and computationally in the protonated thiazole-water system. The formation of a weak hydrogen bond was directly evidenced by a low-frequency shift of the hydrogen-bonded aromatic C-H stretch in the protonated thiazole moiety. For pure thiazole, the pressure dependence of the C-H bands yielded blue frequency shifts. The peak frequency of the aromatic C-H stretch band of protonated thiazole in a dilute D2O solution possesses an unusual nonmonotonic pressure dependence, which indicates enhanced C-H...O hydrogen-bond formation at high pressure. We performed density functional theory calculations to predict the frequency shift of the C-H stretching vibrations. The reorganization of the hydrogen-bonded network may be one of the factors to induce the blue frequency shift to the red frequency shift.
authors.affiliation: Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan. hcchang@mail.ndhu.edu.tw
authors.forename: Hai-Chou
authors.initials: HC
authors.lastname: Chang
authors.forename: Jyh-Chiang
authors.initials: JC
authors.lastname: Jiang
authors.forename: Wen-Wei
authors.initials: WW
authors.lastname: Lai
authors.forename: Jui-San
authors.initials: JS
authors.lastname: Lin
authors.forename: Guan-Ciao
authors.initials: GC
authors.lastname: Chen
authors.forename: Wei-Cheng
authors.initials: WC
authors.lastname: Tsai
authors.forename: Sheng Hsien
authors.initials: SH
authors.lastname: Lin