Optical properties of molecules in solution via hybrid TDDFT/MM simulations

The optical properties of molecules in complex environments were investigated within hybrid time‐dependent density functional theory / molecular mechanics (TDDFT/MM) simulation studies. The potential energy surface in the excited state is described within time‐dependent density functional theory (TDDFT). The solvent is described through a molecular mechanics approach and the effects due to the inhomogeneities of the electric field of the solvent molecules are fully included. The results for different systems including both n → π* and π → π* transitions are discussed. We apply this TDDFT/MM technique to the study of the properties of the ground state and of the first excited singlet state of two different systems: acetone in water and aminocoumarins in water and acetonitrile. Our approach yields quantitative information on the solvent‐induced shifts, both batho‐ and hypsochromic, of the electronic absorption spectra, and on the effect of a protic and an aprotic solvent on the spectral shift.