Interpretation of the magnetic anomalies in Cu(II):Ni(II) bis(diselenocarbamate) crystals

Abstract

Articles you may be interested inInterpretation for the anomaly of the C=O stretching band in benzoic acid crystal J. Chem. Phys. 94, 4446 (1991); 10.1063/1.460634 14N nuclear quadrupole interaction in salicylaldoxime and in Cu(II) doped bis(salicylaldoxime) Ni(II) J. Chem. Phys. 74, 3618 (1981); 10.1063/1.441469Hartree-Fock-Slater-LCAO calculations on the Cu(II) bis(dithiocarbamate) complex; magnetic coupling parameters and optical spectrum A possible interpretation of the relevant magnetic anomalies, recently observed in Cu(II):Ni(II) bis(diselenocarbamate) mixed crystals, is presented. The Cu-Se bond is considered responsible for the large "circularization" (to the value for the free electron) of g about a twofold axis in the molecular plane. Thus it is possible that a weak C 2h distortion of the D 2h symmetry in the complex [mixing of (xz) into the (3z 2_r 2) ground state, or (y z) into the (x y) ground state] may produce both the characteristic angle of approximately 45 0 between the low values of g and the molecular plane and the appearance of a principal value of g slightly lower than the free electron value. It is also clarified why A does not exhibit an analogous rotating effect. Relevant expressions of g and A tensors are deduced in terms of a simple LCAO-MO formalism and implications on the covalent character of the magnetic bonds in the complex are finally discussed.

Low-symmetry effects in electron paramagnetic resonance

“…The approach of Buluggiu and Vera (1973) parallels that of Hitchman et al (196913) and the more recent discussion of Belford et al (1977) and reviewed in $4.1.1. Buluggiu and Vera (1973) explained, in principle, the rotation of g relative to A in the plane normal to the two-fold axis. More recently Keijzers and de Boer (1975a, b) have presented rather more complete calculations using the extended Huckel method to both the monomeric and dimeric structures.…”

“…Keijzers and de Boer (1972) reported use of the iterative extended Huckel molecular orbital method, which had been outlined previously (Keijzers et a1 1972), in calculations of A for copper (N,N-diethyldiselenocarbamate). Buluggiu and Vera (1973) presented a possible interpretation of the copper di-n-butyl diselenocarbamate results due to van Rens et a1 (1970) using an LCAO model based on metal d and ligand p orbitals. The approach of Buluggiu and Vera (1973) parallels that of Hitchman et al (196913) and the more recent discussion of Belford et al (1977) and reviewed in $4.1.1.…”

“…Buluggiu and Vera (1973) presented a possible interpretation of the copper di-n-butyl diselenocarbamate results due to van Rens et a1 (1970) using an LCAO model based on metal d and ligand p orbitals. The approach of Buluggiu and Vera (1973) parallels that of Hitchman et al (196913) and the more recent discussion of Belford et al (1977) and reviewed in $4.1.1. Buluggiu and Vera (1973) explained, in principle, the rotation of g relative to A in the plane normal to the two-fold axis.…”

ESR of Copper in Biological Systems

“…Following the observation of non coincidences between principal 9 and A directions for copper II n-butyl diselenocarbamate crystals by Van Rens et al (1970) and Kirmse et al (1972), Buluggiu and Vera (1973) and Keijzers and de Boer and co-workers (i.e., Attansio et aI., 1976) have shown that it is possible to obtain good agreement with experiment for quite complicated low-symmetry complexes. While many of the copper II sites in proteins may be low-symmetry ones, viz., C2 , C2h , C., Ci , or C b the resolution of the observed spectra do not allow conclusions to be drawn along these lines at the present time.…”

A Study of the Effect of Solvent and Temperature on the Electron Paramagnetic Resonance Parameters and Linewidths of Copper(II)bis(Diethyldithiocarbamate)

“…spin Hamiltonian parameters (g-and A-) with changes in the nature of the ligand (substituent changes) in square planar copper(I1) con~plexes (CuL,) has been well studied and can be said to be fairly well understood (1)(2)(3)(4)(5)(6)(7). The dependence of the g-tensor and hyperfine coupling tensor (A) on the rigid matrix in which the square planar conlplex is situated has also been the subject of extensive study.…”