DFT / TDDFT insights into excited state intra-molecular hydrogen atom transfer mechanism in Liqcoumarin: an EFP1 study

Abstract

The theoretical calculations were carried out on Liqcoumarin (LC) and its water complex $LC+(H_2 0)_4 -[LCH]$ at the ground (S0 ) / first excited states (S1 ) by employing density functional theory (DFT) / state specific time-dependent density functional theory (SS-TDDFT). In LC and LCH, there is an intra-molecular hydrogen bond between hydroxyl group and acetyl group along with four inter-molecular hydrogen bonds in the hydrated molecule. The computational studies of molecular structural parameters, electrostatic potential, NBO analysis, molecular orbital’s, and UV-Vis spectra of both molecules under polar solvents were explored by B3LYP / 6-31G (d,p) / PCM / EFP1 method. The intra-molecular hydrogen atom transpires between hydroxyl to acetyl group in both pure and hydrated molecules confirm the ICT process, and it affirms through potential energy surface (PES) scans.