ИСТИНА

Many chemical compounds, such as halogenide ions and some transition metal complexes in water solutions, demonstrate the so-called "charge-transfer-to-solvent" (CTTS) bands in their optical absorption spectra. These bands are associated with a process of electron ejection from the photoexcited solute onto the nearest solvent molecules, and they are of wide interest in photophysics, photochemistry and condensed phase spectroscopy. Hexaammineruthenium (II) ion is the simplest coordination compound exhibiting a broad CTTS absorption band at 36400 cm-1 in water solution [1]. In our previous investigation [2], we have provided reasonable estimates for the CTTS band position, shape and width using a simple harmonic model for the adiabatic potential surfaces with the parameters taken from the cluster DFT/TDDFT calculations including 16, 21, or 38 solvent molecules explicitly. In order to overcome evident limitations of the cluster model, in the present work, we have utilized a multi-level approach based on ab initio molecular dynamics (MD) simulation of the solvated complex with periodic boundary conditions using CP2K package [3], followed by the CTTS excited state calculations on configurations sampled from the simulated MD trajectories at the TDDFT level using US Gamess package [4]. This approach allows to take into account bulk solvation effects, presence of multiple minima and other effects due to anharmonicity of realistic potential surfaces. It also provides valuable microscopic insights into the possible CTTS band broadening mechanisms discussed in the literature, in particular, those connected with classical dephasing and quantum decoherence phenomena [5]. The work was supported by the Russian Foundation for Basic Research (grant 10-03-00665-a) References: 1. T. Matsubara, S. Efrima, H.I. Metiu, P.C. Ford, J Chem Soc Faraday Trans 75 (1979) 390–400. 2. P.V. Yurenev, M.K. Kretov, A.V. Scherbinin, and N.F. Stepanov, J. Phys. Chem. A 114 (2010) 12804–12812. 3. Quickstep, CP2K Developers Group, http://www.cp2k.berlios.de. 4. M. Schmidt et al, J. Comput. Chem. 14 (1993) 1347–1363. 5. H. Hwang, P.J. Rossky, J. Chem. Phys. 120 (2004) 11380–11385.