UBC Theses and Dissertations
The synthesis and characterization of pyrazine and 2-methylpyrazine complexes of divalent copper and nickel Otieno, Tom
A number of divalent copper and nickel complexes have been prepared and characterized using physical methods such as thermal analysis, vibrational and electronic spectroscopy and magnetic susceptibility measurements. One monovalent copper complex has been isolated as single-crystals and its structure determined by X-ray crystallography. The ligands, L, employed in this study include pyrazine, 2-methyl-pyrazine and pyridine while the anions, X, used are CF₃SO₃⁻, CHSO₃⁻, p-CH₃C₆H₄SO₃⁻ and NO₃⁻. Complexes of the ML₄X₂ type are all characterized as being molecular with both neutral ligands and anions bonded in a unidentate fashion. Spectroscopic evidence indicates that complexes of stoichiometry ML₃X₂ contain both bridging and terminal pyrazine groups whereas in those of the ML₂X₂ type only bridging pyrazine ligands are present. Both types of complexes contain monodentate anions. Compounds of the type MLX₂ are characterized as containing bridging neutral ligands and bridging (sulfonates) or chelating (nitrate) anions. The copper(I) complex (ML₂X) has been found by X-ray analysis to possess both bridging and terminal pyrazine ligands and monodentate sulfonate groups. Magneto-structural correlations have been made for all the divalent metal complexes investigated. All complexes of stoichiometry ML₄X₂ are found to be, as expected, magnetically dilute. All copper(II) complexes containing bridging units, on the other hand, are found to be magnetically concentrated and their magnetic susceptibilities have been analyzed in terms of a linear chain model and a two-dimensional Heisenberg model. In the case of nickel (II) complexes, however, it has been observed that the presence of a bridging network does not necessarily lead to measurable magnetic concentration.
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