Inorganic Chemistry, Vol.34, No.12, 3142-3152, 1995
Polarized X-Ray-Absorption Spectroscopy of Cupric Chloride Dihydrate
We report a detailed polarized single-crystal X-ray absorption spectroscopic study of CuCl2 . 2H(2)O, with measurements at both the copper K-edge and the chlorine K-edge. The angular dependence of both dipole-allowed and quadrupole-allowed transitions is determined in detail for the copper K-edge. The formally dipole-forbidden, quadrupole-allowed Cu K-edge 1s --> 3d transition behaves as a pure quadrupole transition, with no significant dipole contribution. The 1s --> 3d transition is found to have predominantly 3d(x2-y2) character, as expected, but evidence is also given for vacancies in a lower lying d orbital, possibly 3d(x), arising from the presence of d pi-d pi bonding with the chloride ligands. The chlorine K-edge data show a strongly polarized pre-edge resonance at similar to 2821 eV, which can be interpreted in terms of a transition from the chlorine Is orbital to an antibonding orbital with significant contributions from both chlorine 3p and the half-filled copper 3d(x2-y2) orbital.
Keywords:SHAKE-DOWN PHENOMENA;NEAR-EDGE STRUCTURE;BLUE COPPER SITE;FINE-STRUCTURE;K-EDGE;CRYSTAL-STRUCTURE;XANES SPECTRA;PLASTOCYANIN;TRANSITION;COMPLEXES