APPLICATION OF CRYSTAL FIELD THEORY TO THE ELECTRONIC SPECTRA AND STRUCTURE OF 4- AND 6-COORDINATED Ni(II) CHELATES
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Date
1957
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Ohio State University
Abstract
“A calculation of the electronic energy levels in 4- and 6-coordinated Ni(II) complexes was made using Crystal Field Theory. In order to test the theory most rigorously, only the assumptions inherent in its original form were used. Thus, unadjusted experimental free-ion intermultiplet separations were used, and no explicit account was taken of the effect of “exehange energy” on the various states. Only those states of the free ion arising from the ground state configuration were considered, and were characterized by the quantum numbers L and S and a term energy. All such states of the same multiplicity and symmetry were allowed to interact, including those from different terms of the free ion. Calculations were made for 4 pertinent symmetries: octahedral, tetragonal, cis-and trans-planar. The results were employed 1) to assign the symmetry forbidden optical absorption spectra obtained for several types of Ni chelates 2) to explain the multiplieity of the ground states and 3) to explain some observed changes in magnetic moment in going from the solid form to various solvents. In cases where the symmetry was unknown, several plausible assignments of the spectra were made, comparison of which, permitted a prediction of structure. For some chelates with inequivalent ligands, assignment was made for the correct local symmetry and also for the higher symmetry obtained by considering all the ligands to be equivalent. In every case, a more applicable assignment could be made in the lower symmetry. In general, it was possible to explain observed spectra and magnetic properties with very consistent values of parameters. These results indicate that Crystal Field Theory is quite effective in explaining properties of the complex which are closely associated with the central ion.”
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Author Institution: Department of Chemistry, University of California