Solvent Effects on the ESIPT Mechanism of 3-(Benzo[d]thiazol-2-yl)Triphenylen-2-ol: A DFT Investigation

Abstract

The excited-state intramolecular proton transfer (ESIPT) mechanism of 3-(benzo[d]thiazol-2-yl)triphenylene-2-ol (HTpT) in different kinds solvents were calculated, utilizing density functional theory (DFT) and time-dependent density functional theory (TD-DFT). We investigated the effects of five solvents, namely CH3OH (MeOH), CH2CL2 (DCM), Tetrahydrofuran (THF), CHCL3, and Toluene, on the system. Analysis of hydrogen bonding parameters and infrared vibrational spectra in a series of solvents showed the hydrogen bond strengthens with decreasing solvent polarity in the S1 state, a finding supported by our analysis of the interaction region indicator (IRI) function. The energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) was reduced, as the polarity of the solvent decreasing. In addition, the potential energy curves (PECs) in the S0 and S1 states calculated for all solvents indicated that the ESIPT process becomes less feasible as solvent polarity increases, whereas it becomes more favorable with decreasing solvent polarity. Notably, our study identifies Toluene as a specific explicit solvent that promotes the ESIPT process more effectively than other implicit solvents.