title: Long wavelength absorbing carbostyrils as test cases for different TDDFT procedures and solvent models.
abstract: The vertical excitation energies of 3,4-dicyano-6-methoxy and 3,4-dicyano-6,7-dimethoxy carbostyril have been computed with different approximations for the time-dependent density functional theory (TD-DFT) procedure and with different implementations of the continuum solvation model COSMO. Different DFT functionals were tested in TD-DFT and Tamm-Dancoff approximations (TDA) for the excitation energies in the gas phase. TDA-B3LYP showed the best agreement with the experimental data. Then TDA-B3LYP computations were performed combined with the COSMO model of solvation comparing a linear response (LR) and a post-configuration interaction (CI) implementation of the fast solvent reorganization. The post-CI solvent model overestimates the π→π* transitions and strongly underestimates the n→π* transition. The TDA approximation in combination with the linear response implementation of the COSMO solvation model perfectly computes the experimental results. TDA-LR is the most reliable method for the computation of the vertical excitation energies in a solvent. Comparison with explicit solvent calculations shows there is only a minor effect on the energies of the electronic interaction of the solute with the solvent.
authors.affiliation: Institute of Physical and Theoretical Chemistry, Graz University of Technology, Stremayrgasse 9/I, 8010, Graz, Austria, kelterer@tugraz.at.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Kelterer
authors.forename: Georg
authors.initials: G
authors.lastname: Uray
authors.forename: Walter M F
authors.initials: WM
authors.lastname: Fabian
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