K-edge absorption spectra of selected vanadium compounds

High-resolution vanadium K-edge absorption spectra have been recorded for a number of selected vanadium compounds of known chemical structure with use of the synchrotron radiation available at the Stanford Synchrotron Radiation Laboratory (SSRL). The compounds studied include the oxides VO, V₂O₃, V₄O₇, V₂O₄, and V₂O₅; the vanadates NH₄VO₃, CrVO₄, and Pb₅ ({VO₄) }₃ Cl; the vanadyl compounds VOSO₄. 3H₂O, vanadyl bis (1-phenyl-1, 3-butane) dionate, vanadyl phthalocyanine, and vanadyl tetraphenylporphyrin; the intermetallics VH, VB₂, VC, VN, VP, and VSi₂; and V₂S₃ and a vanadium-bearing mineral, roscoelite. Vanadium in these compounds exhibits a wide range of formal oxidation states (0 to +5) and coordination geometries (octahedral, tetrahedral, square pyramid, etc. ) with various ligands. The object of this systematic investigation is to gain further understanding of the details of various absorption features in the vicinity of the K absorption edge of a constituent element in terms of its valence, site symmetry, coordination geometry, ligand type, and bond distances. In particular, the intensity and position of a well-defined pre-edged absorption in some of these compounds have been analyzed semiquantitatively within a molecular-orbital framework and a simple coordination-charge concept.