Intracrystalline and electronic structures of copper(II) complexes stabilized in two-dimensional aluminosilicate

X-ray absorption spectroscopic studies at the Cu K-edge have been performed for [Cu(en)(2)](2+), [Cu(cyclam)](2+), and their intercalated forms of two-dimensional layer silicate to examine how the structural and electronic modifications influence the stabilization of copper complexes in the charged interlayer space. According to the EXAFS analysis, copper complex ions in the layer silicate are stabilized at the center of the siloxane ring, and negatively charged layers are likely to act as axial counteranions. It is spectroscopically confirmed that the covalent bonding character between copper and ligand is enhanced by the intercalation into the silicate layers, depending upon the kind of ligands. There is a good linear relationship between the shoulder peak position of Cu K-edge XANES spectra and d-d transition band position of UV-visible spectra, which means that the former reflects the ligand-to-metal charge transfer effect.