Environmental broadening of the CTTS bands: the hexaammineruthenium(II) complex in aqueous solution

Cluster ab initio quantum chemistry approach is developed to simulate the charge-transfer-to-solvent (CTTS) absorption band and satellite ligand field bands of hexaammineruthenium(II) ion in aqueous solution. Several cluster models, including 16, 21, and 38 water molecules, are explored for this purpose. TDDFT method with long-range corrected BLYP (LC-BLYP) functional is used to obtain the vertical transition characteristics, and DFT B3LYP is used for calculation of the ground state geometry and vibrational frequencies of the solvated complex. A simple harmonic bath model is employed to estimate the absorption bandwidths and coherence decay times with the parameters taken from the quantum chemistry calculations. The present approach provides rather reasonable estimates for the CTTS band position and shape, also giving an additional insight for the mechanism of the CTTS band broadening.