The electronic properties of transition-metal complex ions adsorbed on silica gel. Part III. Copper(II)

Abstract

The polycrystalline electronic reflectance and e.s.r. spectra of a series of copper(II) complex cations (with multidentate nitrogen ligands) adsorbed on silica gel by ion exchange have been examined. In all cases the systems can be described in terms of a ligand competition for co-ordination sites on the adsorbed ion, with the competing ligands being water, surface groups, and the original ligands. The most likely species on the dehydrated gel are the CuN₂O₄(tetragonal-octahedral) or CuN₂O₃(square-pyramidal) chromophores. A tetrahedral or trigonalbipyramidal chromophore is ruled out by the electronic spectra. The e.s.r. spectra are consistent with an axial environment for the copper(II) ions. The fact that there is only slight exchange coupling suggests that these systems approach to an atomic dispersion of the copper(II) ions.