Properties of Na₄KCu（HIO₆）₂·12H₂O and Related Componds

The electronic spectra and XPS of Cu（Ⅲ） complex Na₄KCu（HIO₆）₂·12H₂O and related Cu（Ⅱ） complex Na₆Cu（HIO₆）₂·13H₂O have been investigated. The diffuse reflectance spectrum of Cu（Ⅱ） complex exhibits much more significant absorption at 615nm attributed to d—d transitions than that of Cu（Ⅲ） complex. The intense bands assigned to ligand to metal charge transfer （LMCT） are observed in both complexes. The value of the electron binding energy of Cu2p_3/2 level in the Cu（Ⅲ） complex is 935.7eV, corresponding to Cu3d¹⁰Ḻ² state （Where Ḻ represents a delocalizing hole in a hybrid O2p orbital with its proper symmetry to one of Cu3d orbitals）. It is 1.8eV higher than that of Cu（Ⅱ） complex at 933.9eV. On the basis of comparing Cu2p XPS of YBa₂Cu₃O_7-δ material, it is pointed out that differences among various studies on Cu valences in YBa₂Cu₃O_7-δ are mainly due to easy reduction of higher state on sample surface.