Electronic structure of quinoxaline-2,3(1H,4H)dione and its prototropic species in the ground and excited singlet states

Abstract

The solvent-dependent electronic absorption and fluorescence spectra indicate that quinoxaline-2,3(1H,4H)dione exists in its keto form, even in non-polar solvents, but the deprotonation reaction is observed from its enol form. The protonation reaction in comparison with those of the parent quinoxaline and 1,4-dimethylquinoxaline-2,3-dione suggests that the cation is formed by the gain of a proton on one of the carbonyl groups of the molecule.