Electric properties of the low-lying excited states of benzonitrile: geometry relaxation and solvent effects

Accurate calculations of the dipole moment and the polarizability for the ground and two lowest singlet and triplet excited states of benzonitrile (BN) have been performed by a variety of wave function and density functional theory (DFT) methods. Changes in molecular properties upon the electron excitation strongly depend on the character of an excited state. The vertical dipole moment change and the excess polarizability for the 11B state are smaller than those for the 21A state. In order to estimate adiabatic excited-state properties, corresponding relaxed geometries have been obtained using the PBE0 functional with the aug-cc-pVTZ basis set. The excited-state property values obtained with the long-range exchange corrected DFT methods are in general closer to the coupled cluster (CC) results, although the hybrid DFTs also provide reasonable predictions. Our CCSD adiabatic excess dipole moment value for the 11B state equal to 0.11 D is in excellent agreement with the experimental value. The 21A state appears to be more sensitive to selected method due to an important role of double-excitation effects. Solvent effects on dipole moment and polarizability of BN molecule in its ground and excited states were evaluated using both LR and cLR methods combined with the (TD-)CAMB3LYP/POL approach.