XANES AND EXAFS STUDIES ON THE RHENIUM L-ABSORPTION EDGES OF GRAPHITE-INTERCALATION COMPOUNDS OF RECL5

X-ray absorption measurements were carried out at the Re f L(II,III) absorption edges of graphite intercalation compounds (GICs) of ReCl5 and a series of different rhenium chlorides. The EXAFS analysis of the Re L(III) edges yields a coordination number of six and an average Re-Cl bond length of 234.6 pm for the GICs. This distance as well as the energy shift of the white lines indicate an oxidation state of 4-4.5 for rhenium in its GICs. The analysis of the white lines always reveals larger widths for the L(III) as compared to the L(II) edges. The white lines of the pure metal chlorides in the series +3, +4 and +5 for the oxidation state of Re are shifted to higher energies accompanied by an increase of the intensities. The GICs exhibit the same dependence between energy position and oxidation state, but the intensities are always higher.