Hartree–Fock exchange in time dependent density functional theory: application to charge transfer excitations in solvated molecular systems

The performance of time dependent density functional theory methods for the computation of electronic absorption spectra of molecular solutions is investigated using aqueous acetone as model system. Solute and solvent are treated at the same level of theory. Whereas transition energy and intensity for the intra-molecular 1A2n → π∗ transition are described to good accuracy by a conventional generalised gradient corrected exchange correlation functional (BLYP), explicit inclusion of exact exchange is found to be a necessary requirement to suppress overlap of the carbonyl band with spurious excitations involving transfer of electron charge from or to states with non negligible solvent character.