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Anti-inflammatory Cu(II) dimer complexes of indomethacin with axial solvent donor ligands were characterized by electronic, x-band electron paramagnetic resonance and variable temperature magnetic analysis. Results indicated the complexes' relative insensitivity to changes in the axial ligands. Since the axial ligands were likely to exchange during drug metabolism, results showed that the physical properties and reactivities of indomethacin are likely to be insensitive to the nature of axial ligands.

The first detailed characterization of chromium(V) oxalato complexes using X-band electron paramagnetic spectroscopy is reported. The characterization proceeded with the reactions of Cr(VI) or Cr(V) (Na(Cr(super V)O(ehba)2)) with oxalic acid in acidic aqueous solutions. A new mechanism for the Cr(VI) oxidation of oxalic acid in acidic aqueous solutions is proposed based on data on the structures and reactivities of Cr(V) and Cr(VI) oxalato complexes.

Substituted macrobicyclic hexaamine copper(II) complexes exhibit trigonal and tetragonal distorted structures. The distortions occur both in solution and in solid state and are due to strong Jahn-Teller coupling. Molecular mechanics show that the underlying static geometry was highly tetragonally distorted. Intensity mechanisms of electronic transitions are related to macrobicyclic ligands' trigonal directions.

British farmers’ impressive progress on the environment, nature and the production of healthy, low-carbon food for the British public is under threat from climate change and new trade deals that undermine environmental and welfare standards. Farming can and must be part of the solution to the problems of climate change and biodiversity loss, but farmers need the support and understanding of the public and politicians. [ABSTRACT FROM AUTHOR]

The effects of V(IV) on Cr(V)-induced DNA cleavage reactions and mutations was studied. The results revealed that (Cr O ehba2)1- promotes the cleavage of supercoiled plasmid pUC9 DNA in vitro. VOSO4.5H2O and (V O ehba ehbaH)1-, on the other hand, do not. Moreover, VOSO4.5H2O is a more powerful potentiator of the DNA cleavage than (V O ehba ehbaH)1-. At low concentrations of V(IV) with excess Cr(V), however, a substantial potentiation of Cr(V) mutagenesis exists.

High-field and zero-field electron paramagnetic resonance spectra of polycrystalline [Cr diamsar]Cl3·H2O, [Cr diamsar H2]Cl5·xH2O, and 1% Cr/rac[Co diamsar H2]Cl5·1.5H2O were recorded (diamsar≡1,8-diamino-3,6,10,13,16,19-hexaazabicyclo [6.6.6] eicosane). Combining the high- and zero-field spectra made determination of the spin-Hamiltonian parameters from powder spectra an easy matter, even with two sites in the cobalt host case. Full matrix refined parameters are given, but an iterative perturbation method was used with the actual field B rather than the central field, B0=hν/gμB, to get accurate parameters. Corrected perturbation formulas are given. For a rigid cage ligand like diamsar, there is considerable variation in the spin-Hamiltonian parameter D and evidence that the principal axis of the corresponding interactions does not necessarily lie close to the ligand’s threefold axis. [ABSTRACT FROM AUTHOR]

Describes the design of a zero-field electron magnetic resonance spectrometer used in copper carboxylates. Cryogenic capabilities; Tuning mechanism for sweeping over approximately two octaves; Parallel hyperfine structure; Zero-field terms in the spin Hamiltonian.

The idea that the ratio E/D ≡ λ can be confined by a proper choice of the axis system to the range (0,±1/3) serves as a basis for the standardization of the spin Hamiltonian and the ligand field Hamiltonian for orthorhombic symmetry. Due to recent results on the transformation of the Stevens operators Oqk, relations are given which allow for extension of the standardization to the spin Hamiltonian for paramagnetic centers with spin S≥2. Several EPR studies of 3dn and 4 f n ions in crystals are reconsidered. The results prove the usefulness of the clear choice of the parameters Bqk suggested by the standardization idea. Application of the standardization in the area of the ligand field theory, which seems rather novel, is also considered. Crystal-field parameters for several rare earth ions in garnets are recalculated. An arbitrary choice from among the equivalent sets of the crystal-field parameters used in the review by Morrison and Leavitt (1982) should be replaced by a transformation to the ‘‘standard’’ set. [ABSTRACT FROM AUTHOR]

The single crystal EPR spectra of VO2+ doped ZnSO4·7H2O have been reexamined. The angular behavior confirms the orthorhombic structure and the ion is found to replace zinc–water units. Accurate values of the hyperfine principal values were determined by zero-field EPR (ZFR). One previous publication had incorrect locations of the crystallographic axes, with magnetically inequivalent VO2+ sites wrongly identified as physically inequivalent, and another had suggested a different crystal structure. [ABSTRACT FROM AUTHOR]