DFT and semiempirical study of metal-ligand coupling and its effects on the electronic spectra of ruthenium complexes

Electronic coupling in transition metal complexes and the prediction of their electronic spectra have been topics of interest for a long time. The main objectives of this Dissertation were to study electronic structure and electronic spectra of ruthenium ammino and imino complexes and to investigate how the electronic coupling between metal and ligand affects the electronic spectra of the complex.; First, charge transfer transitions in outer sphere systems, where the coupling between donor and acceptor is minimal, were considered. Electronic spectra of such systems were analyzed, and a new method was proposed to evaluate solution phase ionization energies, electron affinities, and reorganization energies from available spectroscopic data.; Second, a series of complexes, such as [Ru(NH3)5L] 2+, [Ru(NH3)4L]2+, [Ru(L) n]2+, [Ru(L)n(bpy)3-n] 2+, and [Ru(L)nCl2] containing weakly (py, bpy, terpy) and strongly pi-accepting (bqdi, NO+) ligands were studied using density functional theory and semiempirical INDO methods. An electron population analysis using atomic orbital contributions to frontier molecular orbitals, and overlap populations were used to analyze chemical bonding in these series of complexes. The effect of metal-ligand coupling on the electronic spectra of these complexes was investigated. The performances of density functional theory with different exchange-correlation functionals and INDO methods were evaluated to obtain the geometries and electronic spectra of ruthenium ammino and imino complexes.