X-ray absorption near edge structure as a source of structural information

Electronic structure determination using an assembly of conventional and synchrotron techniques: The case of a xanthate complex

The electronic properties of the coordination complex nickel (II) bis-n-propylxanthate, Ni(CH₃(CH₂)₂OC(S)S)₂, were studied by a combination of complementary experimental (both laboratory and synchrotron based techniques) and theoretical methods. Energy differences between HOMOs and LUMOs were determined from UV-visible spectroscopy. The assignment of the transitions were performed with the aid of TD-DFT calculations and based in symmetry considerations. The analysis of the Raman excitation profiles of selected vibrational modes of the complex, taken in resonance with a particular electronic transition, was found to reinforce the electronic assignment. Experimental binding energies of inner and core electrons were determined by PES measurements. Ni K-edge, S K-edge, Ni L-edge, O K-edge and C K-edge XANES spectra were interpreted in terms of the promotion of core electrons to unoccupied electronic levels. An experimental quantitative molecular orbital diagram was constructed using the information extracted from the different techniques.