Solvent electronic polarization effect on the electronic transitions in solution: Charge polarizable reference interaction site model self-consistent field approach

Effect of the electronic polarization in solvent on the solvatochromic shift for the excitation energy of solute molecule is studied by the reference interaction site model self-consistent field (RISM-SCF) method. The electronic polarization in solvent molecule is represented by the charge response kernel (CRK) obtained by ab initio calculations. Employing the CRK, a charge polarizable RISM-SCF method is proposed for describing the electronic structure of solute molecules in solution and estimating the excitation energies. The excitation energy for nπ* transition of acetone is calculated in CH₃CN, CHCl₃, CCl₄, and CS₂ solvents and the solvent electronic polarization effect on the solvation shift is examined. As a result, a blue shifts of 1225, 675, 166, and 92 cm^-1 is obtained in those solvents. Furthermore, the solvation shifts in the transitions to the 1¹B₁, 1¹B², and 2¹A₁ states of pyridine are evaluated in the same solvents. A blue shift is observed for the 1¹β₁← 1¹A₁ transition in all the solvent, while the 2¹A₁ ← 1¹A₁ one shows a red shift.