Evaluation and visualisation of molecular orbitals of natural pigments by density functional theory for their application in photoelectrochemical devices

Abstract

The theoretical study of natural pigments such as delphinidin, petunidin and fuligorubin using density functional theory at the B3LYP/6-31G (d) level is presented to highlight their usefulness for photo electrochemical devices. Ground state geometries, electronic transition energies, oxidation potentials and the essential parameters for their photoelectrochemical behaviour are reported. The ground state oxidation potentials are calculated to be 1.31, 1.68 and 1.25 V (vs. normal hydrogen electrode, NHE) and the excited state oxidation potentials are − 1.35, − 1.12 and − 1.51 V (vs. NHE), respectively. Deprotonation order is determined by calculating proton affinities at different sites which indicates the site of anchoring and charge flow direction.