The effects of axial interactions on electron paramagnetic resonance spectra of copper(II) chelates: weak complexes of copper(II) chelates and chloroform

Magnetic and spectroscopic studies of structure and bonding in hexafluorophosphate and hexafluoroarsenate complexes of copper(II)

“…Moreover, we note that on going from complexes containing the relatively more strongly coordinating fluorosulfate and tosylate anions to those containing PF6-and AsF6-anions, the value of g l l decreases and All increases. This, in fact, parallels the findings of Antosic et al (16) who investigated the epr parameters of weak complexes of copper(I1) P-ketoenolates with chloroform. To try to understand more fully the observed variations in the epr parameters we have evaluated bonding parameters for all of the complexes under discussion.…”

“…The isotropic go and A, values were calculated from the room temperature solution spectra and the g l l and A l l values were obtained from the frozen solution spectra. The values of A, and g, were obtained from the equations 3A, = A l l + 2A, and 3go = gll + 2g, (16). For comparison, values of gll, g,, and All have been estimated from the room temperature powder spectra and these are also given in Table 2.…”

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

“…The large reduction in a, for the pyridines again demonstrates the sensitivity of the hyperfine coupling tensor to strong axial interactions. The results in Table 1 show that the g-value of Cu(DEDC), increases as a, The above solvent dependence of a, and go is in accord with the results of other workers (11)(12)(13)(14)(15)(16)(17). In general, it may be stated that the variation of a, from solvent to solvent is a " fairly insensitive measure of solute-solvent interactions and at best only leads to qualitative conclusions as to whether or not specific axial interactions are important in a particular solvent.…”

“…value is indicative of axial interactions (at the vacant coordination site) (1 1) which, as indicated previously (13), can lead to reduction in the absolute value of a,. Tnese interactions may be of the type described by Antosik et al (11) but it is difficult to provide any well-defined interpretation. The above considerations suggest that carbon tetrachloride, cyclohexane, and 2,6-lutidine are relatively inert solvents as far as axial interactions are concerned.…”

“…The results can be readily interpreted in terms of changes in the admixture of the metal and ligand orbitals together with concomitant changes in the d-d excitation energies which determine the magnitude of the g-and A-tensors (8,9). In particular, large variations in the gand A-tensors are to be expected if specific interactions such as ligand addition or solvation occur at the vacant coordination site of the square planar complex (9)(10)(11)(12). The variations in g and A due to substituent effects are most reliably interpreted using the anisotropic components of the g-and A-tensors (9, 13) rather than the isotropic components (g, and a,), although go has been shown to be reliable (9) in this regard.…”