Spectroscopy and photochemistry of transition metal complexes : a quantum chemical study Transition metal complexes possess unique chemical photoredox and spectroscopical properties that makes them promising candidates as light harvesting antennae or photocatalytic centers in many photochemical devices such as e.g. Ru(II) polypyridyl complexes in dye sensitized solar cells. The knowledge of the photochemical properties of these complexes is therefore of paramount importance to optimize their performance in these devices. To this aim the computation of excited states and photochemical properties can provide useful hints to guide molecular design strategies. Unfortunately the description of electronic excited states is still far from routine as compared to ground state studies and even more that of systems containing metal atoms. ...