Solvation of Copper(II) Ions in Liquid Ammonia

Abstract

X-ray absorption fine structure (XAFS) measurements have been performed at -50 degrees C on a 0.4 mol dm(-)(3) copper(II) nitrate solution in liquid ammonia. Extended X-ray absorption fine structure (EXAFS) spectroscopy was used to determine the coordination number and bond distances for the solvated copper(II) ion in solution. The equatorial ammonia nitrogens are located 2.00 Å from the copper and the axial nitrogen 2.19 Å from the copper. However, it was not possible from the EXAFS analysis alone to conclude whether there was one or two axial nitrogens. Therefore, X-ray absorption near-edge structure (XANES) spectroscopy was combined with discrete variational Xalpha (DV-Xalpha) molecular orbital calculations for a series of five- and six-coordinated models to determine the coordination number and the geometry. The experimental XANES spectrum was best reproduced by a model where the copper(II) ion is pentacoordinated in liquid ammonia in a square pyramidal geometry with the copper(II) ion lifted above the average nitrogen plane.

Cuii in Liquid Ammonia: An Approach by Hybrid Quantum‐Mechanical/Molecular‐Mechanical Molecular Dynamics Simulation

“…At the same time, they concluded from the X-ray absorption near-edge structure (XANES) spectrum that the geometry is square pyramidal with five ammonia ligands coordinated to the copper. The results obtained from EXAFS, XANES [9] and X-ray diffraction studies are not consistent with each other. Coordination numbers of four (square planar), [12,13] five (square pyramidal with Cu II lifted above the average nitrogen plane), [14,15] and six (distorted square pyramidal) [16] nitrogen atoms have been reported.…”

“…The structure of copper II complexes in ammonia has been studied by X-ray absorption fine structure (EXAFS) [9,10] and X-ray diffraction (XRD). [11] The EXAFS results concluded that the Cu II ion was coordinated by five ammonia ligands at equal distances.…”

The influence of Cu(II) on the decay of monochloramine

“…The electron beam energy was 1.5-2.2 Gev, and the average beam current was 80 mA. The monochromator consisted of two parallel Si(1 1 1) crystals with an entrance slit of 2 mm (Valli et al, 1996). The XAFS spectra were collected in fluorescence mode using an argon-filled ionization chambers detector at room temperature ($25°C).…”

X-ray Absorption Spectral Analyses by Theoretical Calculations for TiO2 and Ni-Doped TiO2 Thin Films on Glass Plates

“…[7][8][9][10] The X-ray absorption spectroscopy (XAS) at the L-edges and the X-ray absorption near edge structure (XANES) at the Kedges for 3d transition metals is a powerful tool for investigating the steric and electronic structures of an absorbing atom center. [11][12][13][14][15][16][17] Since the core-hole lifetime of L-edge transitions is longer than that of K-edges, the L-edge XAS has very narrow inherent linewidths, which lead to better resolved features in the spectra, compared to the K-edge XANES. For Ti K-edge XANES, however, the preedge features in the spectra are very sensitive to the structure surrounding the Ti sites, and provide useful information.…”

“…12,16,17,[20][21][22][23][24] So far, nanocrystal TiO2 and Ni ions deposited on a SiO2 crystal have been studied by X-ray absorption experiments. 7,[25][26][27][28] However, TiO2 and Ni ion-doped TiO2 thin films on glasses have been little observed by similar experiments; in addition, the steric and electronic structures of Ti and Ni ions in the thin films on the glasses have not yet been discussed by theoretically analyzing the obtained spectra.…”