Resonant Stimulated X-ray Raman Spectroscopy of Mixed-Valence Manganese Complexes.

Resonant stimulated X-ray Raman spectroscopy of the bimetallic [Mn ^III Mn ^IV (μ-O) ₂ (μ-OAC)(tacn) ₂ ] ²⁺ manganese complex is investigated in a simulation study. Essential biological processes, including water oxidation in photosynthesis, involve charge transfer between manganese sites of different oxidation states. We study a prototypical binuclear mixed-valence transition-metal complex with two Mn atoms in different oxidation states surrounded by ligand structures and employ a pump-probe sequence of resonant X-ray Raman excitations to follow the charge transfer occurring in the molecule. This allows us to generate and monitor valence-electron wave packets at selected regions in the molecule by exploiting element-specific core-excited states. A two-color protocol is presented, with pump and probe pulses tuned to the Mn and N K-edges. A natural orbital decomposition allows the visualization of the electron dynamics underlying the signal.