Transition metal complexes represent a unique class of photoactive materials, however, the interpretation of the experimental data on these compounds is hindered by the complexity of the recorded signals and requires theoretical modeling. This cumulative thesis describes theoretical approaches to calculate various spectroscopic observables for the photon-in/photon-out and photon-in/electron-out events. The applications include simulation of elementary steps of photocatalytic water splitting and unraveling different aspects of coordination chemistry by means of X-ray spectroscopy.<eng>
