ESR Studies of Covalent Copper Complexes with a Rhombic Arrangement

Abstract

A method of calculation of bond parameters is proposed for magnetic molecular orbitals which describe the 3d9 configuration in the case of complexes with a rhombic surrounding (D2h symmetry), when the experimental spin Hamiltonian is known. This treatment contains as a particular case that of Kivelson et al. for square planar structures and allows us to evaluate both the anisotropic presence of unpaired spin at the various ligands, and the mixing of the d3z2−r2 orbital in the ground state which is essentially dx2−y2. Applications of this treatment in calculating the bond parameters in the CuCl2·2H2O and CuF2·2H2O compounds allow a comparison between the covalent characters of the Cu–Cl and Cu–F bonds in a similar surrounding. The results show that there is a relevant spin density at the halide ions in both compounds and that, in CuCl2·2H2O, the anisotropy of covalence in the principal plane of coordination is strong. The reliability of the proposed criteria is considered by a comparison between the covalence values obtained following our method and those obtained directly from the extrahyperfine structure in the case of a square planar copper complex.

EPR and Spectral Studies of a Molecular and Crystal Structure of Cu (3,5-dimethylpyridine)3(NO3)2

“…It is especially easy for two inequivalent sites [13,14], i.e. for monoclinic crystals and when local g 2 -tensors have axial symmetry [15]. Below we will summarize results for two-center case and then we will introduce a new result for four-center case.…”

Two-dimensional NMR measurement and point dipole model prediction of paramagnetic shift tensors in solids

“…This yields the lowest overall error in the predicted NMR parameters, which deviate less than 5% from the measured values. This is similar to the [84], and are applied here to single-zeta Slater wave functions [90] for the copper 3d, chloride 3p, and oxygen 2p orbitals, ignoring contributions due to mixing of the ligand s-orbitals.…”

“…al. [84] in their EPR study. Though the ultimate values of f Cl and f O we obtain here surely reflect an exaggerated overlap, the fact that they are pulled toward the results of these population analyses lends credibility to the notion that the destructive interference in the bonding regions can be modeled with dipole sources while generating accurate paramagnetic shift tensor parameters.…”

“…Using a g-tensor [84] that is diagonal in the molecular frame defined in Fig. 7 with components g xx = 2.102, g yy = 2.331, g zz = 2.047, transformed into the crystal frame as necessary for the two inequivalent gtensor orientations, we summed over all copper nuclei within a given distance from the 2 H nucleus and averaged the result according to Eqs.…”

Electron paramagnetic resonance spectroscopy of Cu2+ in hen egg-white lysozyme.

“…There has been extensive study, both experimental and theoretical, of the relationships between the principal values of ge for Cu2+ complexes and the chemical nature and geometrical arrangements of ligands (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25). On the basis of (i) these previous studies, (ii) our measured principal values of g' and A, and (iii) the x-ray diffraction work of Teichberg et al (1980) 5247 (1), we conclude that the four Cu2+ ions that produce our A and A' spectra are coordinated by six oxygens of water moleculesy in an octahedral arrangement with tetragonal elongation along the U' axis, and with small rhombic distortion.…”