Absorption and luminescence spectroscopy of transition metal compounds: from coordination geometries to excited-state properties

Absorption spectra of transition metal compounds provide important experimental information for the understanding of their chemistry. The combination with luminescence spectra yields quantitative insight on excited-state properties, in particular from spectra with resolved vibronic structure measured at low temperature. Three categories of complexes are used to illustrate how their electronic structure can be characterized in detail. The first examples are aquo complexes of first row d-block metal ions with absorption spectra showing interference dips, the second category are trans-dioxo rhenium(V) complexes with metal-ligand single and double bonds leading to luminescence spectra with characteristic vibronic structure, and finally square-planar complexes of palladium(II) and platinum(II) with large changes of luminescence intensities and wavelengths induced by external pressure are presented.