On the role of solvent effects on the electronic transitions in Fe(II) and Ru(II) complexes

Solvent effects on the vertical excitations of complexes with spin crossover are studied with CASPT2 and time-dependent DFT techniques. The geometry of the [Fe(phen)(3)](2+) complex was optimized with DFT using the PBE0 functional, and subsequently, the absorption spectrum was calculated with CASPT2. The spectrum is in good agreement with experiment and the effects of the solvent were found to be small as long as the symmetry of the complex is maintained. The on-set of the MLCT band was found to be shifted by 0.4 eV, which we attribute to the lack of thermal motion in our treatment. The large solvent effects on some of the excitations in trans (Cl)-Ru (bpy) Cl-2(CO)(2) are reproduced both with TD-DFT and CASPT2 through a COSMO or PCM treatment of the solvent. (C) 2013 Elsevier B. V. All rights reserved.