Electronic Structure of ReO3Me by Variable Photon Energy Photoelectron Spectroscopy, Absorption Spectroscopy and Density Functional Calculations

Valence photoelectron (PE) spectra have been measured for ReOsMe using a synchrotron source for photon energies ranging between 20 and 110 eV. Derived branching ratios (BR) and relative partial photoionization cross sections (RPPICS) are interpreted in the context of a bonding model calculated using density functional theory (DFT). Agreement between calculated and observed ionization energies (IE) is excellent. The 5d character of the orbitals correlates with the 5p - 5d resonances of the associated RPPICS; these resonances commence around 47 eV. Bands with 5d character also show a RPPICS maximum at 35 eV. The RPPICS associated with the totally symmetric 4a1 orbital, which has s-like character, shows an additional shape resonance with an onset of 43 eV. The PE spectrum of the inner valence and core region measured with photon energies of 108 and 210 eV shows ionization associated with C 2s, O 2s, and Re 4f and 5p electrons. Absorption spectra measured in the region of the 01s edge showed structure assignable to excitation to the low lying empty "d" orbitals of this d^o molecule. The separation of the absorption bands corresponded with the calculated orbital splitting and their intensity with the calculated 0 2p character. Broad bands associated with Re 4d absorption were assigned to (2)5/2 and 2D3/2 hole states. Structure was observed associated with the CIs edge but instrumental factors prevented firm assignment. At the Re 5p edge, structure was observed on the 2P3/2 absorption band resulting from excitation to the empty "d" levels. The intensity ratios differed from that of the 01s edge structure but were in good agreement with the calculated 5d character of these orbitals. An absorption was observed at 45 eV, which, in the light of the resonance in the 4a1 RPPICS, is assigned to a 4a1 - ne, na2 transition. The electronic structure established for ReO3Me differs substantially from that of TiCI3Me and accounts for the difference in chemical behavior found for the two complexes.