DFT / TDDFT insights into excited state intra-molecular hydrogen atom transfer mechanism in Liqcoumarin: an EFP1study

Abstract

The theoretical calculations were carried out on Liqcoumarin (LC) and its water complex LC+(H 2 0) 4 -[LCH] at the ground (S 0 ) / first excited states (S 1 ) 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 2 acetyl group in both pure and hydrated molecules confirm the ICT process and it affirms through potential energy surface (PES) scans.