NMR line shape studies of solids: Probing molecular and electronic structure via experiment and simulation.
Date
1991
Authors
Power, William Patrick.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
The nuclear magnetic resonance line shapes of solid compounds are used to gain new and fundamental information on several chemical systems. Analysis of the $\sp{31}$P nmr line shapes of several metal-phosphorus systems is used to characterize the anisotropic nature of the $\sp{31}$P chemical shielding and metal-phosphorus indirect spin-spin coupling. This work has revealed that substantial anisotropies exist in the indirect spin-spin coupling between $\sp{31}$P and $\sp{199}$Hg or $\sp{195}$Pt. In the mercury(II) phosphines, (HgPR$\sb3$(NO$\sb3)\sb2\rbrack\sb2$, these anisotropies are quite large, of the order of 5 kHz, for couplings that possess isotropic values of approximately 10 kHz. Although the isotropic $\sp{31}$P-$\sp{199}$Hg indirect spin-spin couplings are larger in the mercury(II) phosphonates, HgP(O)(OEt)$\sb2$X, this study indicates that the anisotropies in these couplings are much smaller. In the square-planar platinum(II) bisphosphine complexes, Pt(PR$\sb3)\sb2$Cl$\sb2$, the $\sp{31}$P-$\sp{195}$Pt indirect couplings are found to possess anisotropies in the indirect spin-spin couplings of at least 1 to 2 kHz, although a dependence of these values on the geometry of the complex cannot be determined. These findings are significant as they demonstrate that the indirect spin-spin coupling between $\sp{31}$P and some metal nuclei is not dominated by the Fermi contact mechanism, as has been commonly assumed. The nmr line shapes of half-integer spin quadrupolar nuclei are found to be sensitive to the relative orientation of the chemical shielding and quadrupolar interactions, and a method to interpret such line shapes is proposed. This is used to simulate the $\sp{133}$Cs nmr powder spectra of Cs$\sb2$CrO$\sb4$ at four magnetic fields, as these interactions are not aligned in this compound.
Thesis (Ph.D.)--Dalhousie University (Canada), 1991.
Thesis (Ph.D.)--Dalhousie University (Canada), 1991.
Keywords
Chemistry, Analytical.