Theoretical study of the excitation of proflavine H-dimers in an aqueous solution: the effect of functionals and dispersion corrections.

Analysis of the ground and excited states of the H-dimer of the proflavine dye cation (PF) in an aqueous solution was performed using the DFT/TD-DFT method with an implicit specification of the aqueous environment and using various hybrid functionals (APFD, B2PLYP, B3LYP, B3PW91, BMK, CAM-B3LYP, M05, M052X, M06, M062X, M06HF, mPW2PLYP, PBE0, PW6B95, and ωB97XD), Grimme dispersion corrections, and Becke-Johnson damping. To our knowledge, this is the first theoretical study on the dimerization of charged monomers. The use of the B2PLYP, B3LYP, B3PW91, BMK, CAM-B3LYP, PBE0, M05, mPW2LYP, and PW6B95 functionals without additional dispersion corrections led to dimer dissociation due to Coulombic repulsion between PF cations.

Coumarin 343 in aqueous solution: theoretical analysis of absorption.

Vibronic coupling and hydration were taken into account when describing the absorption of coumarin C343 (both neutral and anionic forms) in an aqueous media. It was shown that the B3LYP functional with the 6-31 +  + G(d,p) basis set and the IEFPCM solvent continuum model give theoretical vibronic absorption spectra, which are coincide with the experimental ones. Of the structural differences between C343 and C343, there is a different twisting of the carboxyl group additionally changing due to excitation.