Articles you may be interested inHartree-Fock-Slater-LCAO calculations on the Cu(II) bis(dithiocarbamate) complex; magnetic coupling parameters and optical spectrum Further magnetic and structural studies have been made of the bis(N ,N ---diethyldithiocarbamato) iron(III)X complexes (X = CI-, Br-, 1-, SCN-). The 1-homolog is antiferromagnetic (TN = 1.9 oK), while the SCN-derivative is a simple paramagnet (to 1.4 oK). The crystal structure of the paramagnetic bromo derivative was found to be nearly identical to that of the ferromagnetic chloro homolog. The different collective magnetic properties of the chloro and bromo homologs arise from combined exchange and uniaxial crystal field interactions. Using known crystal field parameters and a molecular field description of magnetic interactions, an effective intermolecular exchange constant of 0.12 ± 0.03 oK is derived. Exchange broadened paramagnetic resonance spectra are shown to correlate well with the collective magnetic behavior of the complexes. Solution proton NMR data are interpreted in terms of d-electron delocalization to the dithiocarbamate ligand 1T-type orbital system. 990
621sphere shift is expected to be proportional to the effective magnetic moment, other things being equal.The apparent variation of Feff with temperature was incorporated in the data-fitting process and showed no significant change in the kinetic parameters for FeTMpyP, while for FeTPPS about a 30% change in k , was found. The data in the latter case do not define kl as well, due mainly to the faster rate of exchange which has less influence on the relaxationThe TZM results are interesting in that the lack of field dependence and the negative E, are not consistent with only the Bloembergen-Morgan modellg for electron-spin relaxation. We considered other possible relaxation mechanisms including of ~~1 7 0 . 1 1 nuclear quadrupole interaction and anisotropic g factors but could not draw any firm conclusions from the data at hand. In general, physically unrealistic parameters were required. This problem does not affect the kinetic conclusions seriously but deserves more study in its own right.Acknowledgment.
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