A hybrid TDDFT/MM investigation of the optical properties of aminocoumarins in water and acetonitrile solution

We present a hybrid Time-Dependent Density Functional /Molecular Mechanics (TDDFT/MM) simulation study on the optical properties of aminocoumarins in gas phase and solution. As solvation is described through a molecular approach, the effects due to the inhomogeneities of the electric field of the solvent molecules are fully included. We focus on the ground state and first excited singlet state properties of C151, C35 and C153, three aminocoumarins for which a homogeneous set of experimental data is available. Our approach is able to give quantitative information on the redshifts in water and acetonitrile, two solvents which show different H-bonding properties. In addition, it is able to quantify the effects of chemical substituents, such as the spectral redshift due to the increased alkylation at the amino position.