Theoretical study on excited state intramolecular proton transfer mechanism of thiazole complex in different kinds of solvents

Abstract

The excited state intramolecular proton transfer (ESIPT) processes of 3-(benzo [d]-thiazol-2-yl)-2-hydroxy-5-methoxybenzaldehyde (BTHMB) in four kinds of solvents were studied using density functional theory (DFT) and timedependent DFT (TDDFT) method. As the solvent dielectric constant decreases, the strength of hydrogen bonds (H-bonds) in the excited state decreases. After photoexciation, the electron density rearrangement could be affected by the solvents, while the degree of charge transfer and the hydrogen bond interaction in the excited state became lower as the solvent dielectric constant decreased. The potential energy curves displayed the complete process of ESIPT, indicating that the ESIPT process of BTHMB was affected by the solvent polarity. When the solvent dielectric constant decreased, the tendency of proton transfer followed the trend: acetonitrile (ACN) > dichloromethane (DCM) > chloroform (CHCl 3 ) > 1,4-dioxane (DOX). Therefore, the ESIPT process was affected by the solvent polarity and became more difficult to occur as the solvent dielectric constant decreased. K E Y W O R D Sexcited state intramolecular proton transfer, hydrogen bond, potential energy curves, solvent polarity

Effects of solvents on excited‐state proton transfer behaviors and photophysical properties of 3NTF

“…These studies can help us further understand the excited state proton transfer process. [35][36][37] Since the ESIPT reaction process is easily affected by many factors, such as molecular structure, substituents, and solvents, [38][39][40] scientists have extensively studied the compounds with ESIPT using experimental and theoretical methods to understand the microscopic mechanism and reaction kinetics of the ESIPT process [41][42][43][44] and can adjust its optical response to design excellent fluorescent and phosphorescent photonic materials. 45 In recent years, the influence of solvent polarity on the chemical properties of materials has attracted much attention.…”

Spectroscopic and mechanistic insights into solvent mediated excited-state proton transfer and aggregation-induced emission: introduction of methyl group onto 2-(o-hydroxyphenyl)benzoxazole

“…The ESIPT emission improves fluorescence efficiency by preventing unnecessary self-absorption and internal filtering effects. 2–4 However, the fluorescence properties from the ESIPT reaction are easily affected by the surrounding medium and functional groups 5–10 due to the transient nature of the enol–keto tautomerization process. The introduction of substituents with different electronic effects at the ortho-position could result in a blue emission (469 nm) of 2-(2′-hydroxyphenyl)benzothiazole (HBT) derivatives red-shifted to 630 nm.…”