Multiple K-edge XAS for the structural analysis of thiophenolate bridged heterotrinuclear complexes

A multiple K-edge X-ray absorption spectroscopic (XAS) approach to determin e the structural parameters of an isostructural series of heterotrinuclear thiophenolate-bridged metal-complexes of the general formula [LFeCrFeL]nt ( with n=1,2,3) is presented. The analysis focuses on the variation of the me tal-metal distances and the metal-sulfur distances with the cluster charge n. XAS measurements on the Fe, Cr, and S-Kedges were performed to allow a f it of these distances from these constituent elements. Results show that 3 3 atoms and 3 N atoms coordinate each of the terminal Fe atoms, whereas 6 S atoms coordinate the central Cr atom. This symmetry allows extracting stru ctural information with high accuracy especially when the spectra obtained at different edges are refined at the same time. A decrease of the metal-me tal distance with increasing cluster charge is also derived from this multi ple-edge analysis.