title: Theoretical insight into the excited-state intramolecular proton transfer mechanisms of three amino-type hydrogen-bonding molecules.
abstract: Excited-state intramolecular proton transfer (ESIPT) dynamics of the amino-type hydrogen-bonding compound 2-(2'-aminophenyl)benzothiazole (PBT-NH2) as well as its two derivatives 2-(5'-cyano-2'-aminophenyl)benzothiazole (CN-PBT-NH2) and 2-(5'-cyano-2'-tosylaminophenyl)benzothiazole (CN-PBT-NHTs) were studied by the time-dependent density functional theory (TD-DFT) approach with the B3LYP density functional, and their absorption and emission spectra were also explored at the same level of theory. A good agreement is observed between the theoretical simulations and experimental spectra, indicating that the present calculations are reasonably reliable. In addition, it is also found that the energy barriers of the first excited singlet state of the three targeted molecules along the ESIPT reaction are computed to be 0.38, 0.34 and 0.12eV, respectively, showing the trend of gradual decrease, which implies that the introduction of the electron-withdrawing cyano or tosyl group can facilitate the occurrence of the ESIPT reaction of these amino-type H-bonding systems. Following the ESIPT, both CN-PBT-NH2and CN-PBT-NHTs dye molecules can undergo the cis-trans isomerization reactions in the ground-state and excited-state potential energy curves along the C2-C3 bond between benzothiazole and phenyl moieties, where the energy barriers of the trans-tautomer→cis-tautomer isomerizations in the ground states are calculated to be 0.83 and 0.34eV, respectively. According to our calculations, it is plausible that there may exist the long-lived trans-tautomer species in the ground states of CN-PBT-NH2and CN-PBT-NHTs.
authors.affiliation: Institute of Environmental and Analytical Sciences, College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, People's Republic of China.
authors.forename: Beibei
authors.initials: B
authors.lastname: An
authors.affiliation: Institute of Environmental and Analytical Sciences, College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, People's Republic of China.
authors.forename: Huijuan
authors.initials: H
authors.lastname: Yuan
authors.affiliation: Institute of Environmental and Analytical Sciences, College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, People's Republic of China.
authors.forename: Qiuling
authors.initials: Q
authors.lastname: Zhu
authors.affiliation: Institute of Environmental and Analytical Sciences, College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, People's Republic of China.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Li
authors.affiliation: Institute of Environmental and Analytical Sciences, College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, People's Republic of China. Electronic address: xgguo@henu.edu.cn.
authors.forename: Xugeng
authors.initials: X
authors.lastname: Guo
authors.affiliation: Institute of Environmental and Analytical Sciences, College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, People's Republic of China. Electronic address: zhangjinglai@henu.edu.cn.
authors.forename: Jinglai
authors.initials: J
authors.lastname: Zhang
keywords: Cis-trans isomerization; DFT/TD-DFT; ESIPT; Intramolecular hydrogen bond; Potential energy curve