Electron dynamics within Ru-2,2′-bipyridine complexes—an N1s core level excitation study

Abstract

The dynamics of electron transfer within an excited ruthenium complex as well as between a ruthenium complex and a nanostructured TiO2 film is addressed on the core hole few femtosecond lifetime scale. The ruthenium complexes studied are Ru(bpy)32+·2Cl− (where bpy is 2,2′-bipyridine) as well as Ru(bpy)2(dcbpyH2)2+·2PF6− (dcbpy is 4,4′-dicarboxy-2,2′-bypyridine) anchored to a nanostructured TiO2 surface, where the latter system constitutes the photoactive part of a dye-sensitized solar cell. The N1s core level of the ruthenium complexes was excited by using synchrotron radiation, and the experimental techniques used were X-ray absorption spectroscopy (XAS) and resonant photoelectron spectroscopy (RPES). The occupied molecular orbital structure and the N1s partial density of unoccupied states are mapped and compared to calculated orbital structures.