Synthesis and Excited State Proton Transfer (ESPT) Studies of 2-(6-Substitutedbenzo[d]Thiazol-2-Yl)Naphthalen-1-Ol Derivatives.

This study reports the rapid intramolecular proton transfer studies upon photo excitation of 2-(benzo[d]thiazol-2-yl)naphthalene-1-ol derivatives, yielding tautomer emission with large Stokes shift. Employing photophysical studies, density functional theory (DFT) and, time-dependent density functional theory (TD-DFT) methods, we scrutinize excited state intramolecular proton transfer (ESIPT) modulation over varying solvent polarities. Analysis of UV-Visible and fluorescence spectra, alongside exploration of hydrogen bond dynamics, reveals solvation effects on the excited state proton transfer process. Theoretical vibrational spectra confirm enhanced hydrogen bond strength in the excited state which is sensitive to the solvent polarity. Energy profile curves and the scatter graph depict impact of solvent polarity on ESIPT. Additionally, molecular interactions and X-ray diffraction studies of the title compound 4a are presented.