LAUSR

Abstract 2-(2-Hydroxyphenyl) benzothiazole molecule was synthesized in experiment (Xu et al., 2017), under solvent environments molecular photophysical phenomena were observed, while this experimental work failed to qualitatively unveil the effect of solvent environments on photophysical and photochemical properties. For the first time the mechanism of excited-state intramolecular proton transfer and solvatochromic effect were in depth investigated based on time-dependent density functional theory methods in this research. Calculated absorption and emission spectra peaks were very agreement with the relative values that observed in experiment. Upon photo-excitation process the frontier molecular orbitals and charge-transfer excitation degree were portrayed and analyzed in different solvents, unraveling the solvatochromic effect on spectral properties. Optimal normal HBT-H, isomer HBT-T and anion HBT-A structures were calculated in different solvents, the decreasing order of intramolecular hydrogen bond strength (PhMe > CH3Cl > CH2Cl2 > ACN > DMF) under different solvents were obtained by comparing the bond parameters of hydrogen bond and corresponding infrared vibrational frequencies. More importantly, calculated Hirshfeld charges of donor and acceptor atoms essentially explained the effect of solvent polarities on excited-state intramolecular hydrogen-bond intensity. Because hydrogen bond interaction offered driving force for proton transfer reactions, the effect of solvent polarities on excited state intramolecular proton transfer reaction mechanism was further explained by calculating reactive activation energies.