Electronic Structure, Optical and Electrochemical Properties of Malvidin Molecule Extracted From Grapes
Ion Iosub, Francois Kajzar, Malgorzata Makowska-Janusik, Aurelia Meghea, Irina Geana and Ileana Rau
Spectroscopic, cyclic voltammetry and theoretical studies of electronic structure of a p electron conjugated natural anthocyanine, namely malvidin are presented and discussed. The molecule lacks center of inversion and exhibits an intramolecular charge transfer. It presents a large absorption band with maximum absorption at 270 nm and a weaker charge transfer band at 545 nm in methanol and ethanol solutions. As consequence a noticeable solvatochromic effect is present. The molecule exhibits also photoluminescence, whose spectrum is significantly modified when put in deoxyribonucleic acid environment. The cyclic voltamometry study allows to locate the HOMO level at –5.5 eV. Coupled with the optical absorption spectrum one gets for LUMO level position at –3.6 eV, in good agreement with theoretical calculations performed within the density functional theory (DFT), implemented in DMol3 package.
Keywords: Anthocyanin, malvidin, HOMO level, LUMO level, solvatochromic effect, cyclic voltammetry, optical bandgap, fluorescence, density functional theory