Exploring electron donor and acceptor effects: DFT analysis of ESIPT/GSIPT in 2-(oxazolinyl)-phenols for photophysical and luminophore enhancement.

This article focuses on the computational investigation of the effects of electron-donating groups (EDGs) and electron-withdrawing groups (EWGs) on the excited-state intramolecular proton transfer (ESIPT) and ground-state intramolecular proton transfer (GSIPT) mechanisms in substituted 2-(oxazolinyl)-phenol derivatives. Using density functional theory (DFT) and time-dependent DFT (TDDFT), the study reveals that EDG substitutions enhance absorption and emission wavelengths and reactivity, while EWG substitutions lower activation barriers for proton transfer and increase molecular stability. The research also examines ionization potentials, electron affinities, reorganization energies, and fluorescence properties, finding that EDGs improve hole mobility whereas EWGs enhance electron transport. Quantum theory of atoms in molecules (QTAIM) analysis supports the stronger intramolecular hydrogen bonding in the enol form and greater stability of EWG-substituted keto forms. These findings provide theoretical guidance for designing organic luminophores with tailored photophysical properties for optoelectronic applications.