Solvent dependence of ESIPT process in 2-(2-carbonmethoxy-3,4-dichloro-6-hydroxyphenyl) compounds

After the synthesis of 2-(2-carbonmethoxy-3, 4-dichloro-6-hydroxyphenyl) (Compound 1), Elena V. Vetrova et al. found that it has different photophysical phenomena in the different solvent environment [Dyes and Pigments 180 (2020) 108417]. However, there is still no detailed theoretical research for this phenomenon. Therefore, based on the density functional (DFT) and time-dependent density functional (TD-DFT) methods, under different solvent conditions, the excited state intramolecular proton transfer process (ESIPT) of Compound 1 is investigated in this work. For Compound 1, the bond parameter analysis of the optimized structure confirms that the excited state hydrogen bond interaction is enhanced. The photophysical properties show that the theoretically simulated vertical transition energy is in good agreement with the experimental spectral value. Based on the optimized geometric structure, the frontier molecular orbital isosurface is drawn, and the redistribution of electron density in different solvents is depicted, which intuitively explain the changes in the photophysical properties of Compound 1. Though the calculated potential energy curves, we further explain that ESIPT process are easier to occur from Heptane, Dioxane, Toluene to THF.