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|Title:||Electron Paramagnetic Resonances Studies of High Symmetry Molybdenum(v) and Solvent Effects of Square Planar Copper(ii) Complexes|
|Author(s):||Liczwek, Deborah Lynn|
|Department / Program:||Chemistry|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||Frozen solutions of a series of Ca-S and Cu-O complexes; ('63)Cu(dtc)(,2), bis-diethyldithiocarbamato-copper(II), ('63)Cu(mnt)(,2)('-2), bis(1,2-dicyano-1,2-dithioethylene)cuprate(II), ('63)Cu(imnt)(,2), bis(1,1-dicyano-2,2-dithioethylene)cuprate(II), ('63)Cu(acac)(,2), bis(acetylacetonate)copper(II), ('63)Cu(dpm)(,2), bis(2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II), ('63)Cu(dbm)(,2), bis(1,3-phenyl-1,3-propanedionato)copper(II), ('63)Cu(bzac)(,2), bis(1-phenyl-1,3-butanedionato)copper(II) show highly solvent-dependent electron paramagnetic resonance spectra at (TURN)35, (TURN)9.5, and (TURN)3.7 GHz. The general increase of linewidth with frequency reveals the effects of g strain and the value of low-frequency EPR spectroscopy for frozen solutions. Simultaneous computer simulations of both the 9.5 and 3.7 GHz spectra were required for accurate spin-Hamiltonian parameters. Axial coordination by pyridine increases the copper nuclear quadrupole coupling interaction, in some cases, by an order of magnitude. The principal nuclear quadrupole coupling constant for all copper(II) compounds shows consistent behavior, increasing with symmetry of the coordination sphere, and pointing to a strong contribution of ligand charges to the effective field gradients.
Secondly, frozen solution EPR spectra of a monomeric molybdenum(V) complex, tetrakis(N,N-diethyldithiocarbamato)molybdenum(V)chloride show little or no nuclear quadrupole coupling effects as with the copper frozen solutions, simultaneous computer simulations of 35, 9 and 3 GHz spectra were computed for accurate determination of spin-Hamiltonian parameters. In the dodecahedral structure the molybdenum resides in a highly symmetric site. This complex suggests either an upper or lower bound for the correlation of site geometry with nuclear quadrupole coupling constants. This is discussed in the context of other nuclear quadrupole coupling constants for 3 other monomeric molybdenum(V) complexes.
The general increase in linewidth with frequency and nuclear states, m, reveals the effects of g strain and A strain, respectively. Attempt is made to correlate this to bonding interactions in the Mo(dtc)(,4) complex.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1982.
|Date Available in IDEALS:||2014-12-15|