Date of Award
Chemistry and Biochemistry
Schurko, Robert (Chemistry and Biochemistry)
CC BY-NC-ND 4.0
This thesis demonstrates the application of solid-state nuclear magnetic resonance (SSNMR) spectroscopy to probe the structure of a variety of inorganic complexes and materials, many of which find applications in catalysis. Particular focus is given to SSNMR spectroscopy of "exotic" and unreceptive NMR nuclei. Complimentary characterization techniques such as quantum chemical calculations and X-ray diffraction experiments are also employed. The initial focus of the thesis is on the characterization of crystalline molecular metallocenes by 35Cl, 47/49Ti and 91Zr SSNMR spectroscopy. All of these nuclei are considered to be unreceptive for NMR experiments due to a combination of low natural abundance, low resonance (Larmor) frequency and/or extreme broadening by anisotropic NMR interactions. It is demonstrated that with the combination of modern pulsed NMR techniques and high magnetic fields, SSNMR spectra of these nuclei in metallocenes can be rapidly acquired. Correlations are made between the symmetry and structure of the metallocene species, and the observed electric field gradient (EFG) and chemical shift (CS) tensor parameters extracted from the SSNMR spectra. Preliminary results from SSNMR studies of model heterogeneous metallocene catalysts are also presented. 45Sc SSNMR spectroscopy of simple coordination complexes is investigated. Simple coordination complexes were investigated because most previous 45Sc SSNMR studies have been limited to extended systems with poorly defined structures. SSNMR experiments are also employed to investigate the molecular structure of a heterogeneneous scandium catalyst, microencapsulated Sc(OTf)3. 207Pb SSNMR in conjunction with quantum chemical calculations are used to investigate the electronic structure of a series of lead(II) thiolate complexes. Frequently, lead(II) complexes possess stereochemically-active lone electron pairs. The observed and calculated 207Pb CS tensor parameters are utilized to probe the electronic configuration of the lead(II) complexes. The utility of frequency swept WURST pulses for the acquisition of nuclear quadrupole resonance (NQR) spectra is investigated. The WURST pulses are demonstrated to be particularly useful for locating a NQR of unknown frequency and for acquiring wideline NQR spectra. The utility of WURST pulses for optimizing the configuration of NQR/NMR spectrometer systems is also demonstrated.
Rossini, Aaron, "Characterization of Inorganic Catalysts and Materials by Solid-State NMR" (2010). Electronic Theses and Dissertations. 396.