Electronic structures and spectra of quinoline chalcones: DFT and TDDFT-PCM investigation

The structures and electronic absorption spectra of quinoline chalcones have been investigated with density functional theory (DFT) and time-dependent density functional theory (TDDFT). The relationship between the structure and absorption spectrum and the effects of substituents, solvents, elongation of the conjugate chain as well as differing positions of the carbonyl group in the conjugate chain on electronic spectra have been discussed. It turns out that the hybrid PBE1PBE functional with the 6-31G basis set provide reliable λ_max when the solvent effects are included in the model. Comparisons with experimental values lead to a mean absolute error of 21.5 nm (0.20 eV). Moreover, the observed substituent and solvent effects are reproduced by calculation qualitatively. The calculation reveals that the maximum absorption band mainly results from the π → π^* transition from HOMO to LUMO.