Date of Award
Chemistry and Biochemistry
Robert W. Schurko
Pure sciences, Inorganic complexes, Organometallic, Ultrawide-line solid-state NMR spectroscopy
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Ultra-wideline (UW) powder patterns (breadth sizes > 300 kHz) are difficult to acquire using conventional NMR methods because of limited excitation bandwidths and/or low signal intensities. This thesis will demonstrate the application of solid-state UWNMR spectroscopy and complementary techniques such as X-ray diffraction and theoretical calculations, to examine nuclear environments of chemical materials.
27Al UWNMR experiments were conducted in a frequency-stepped manner on coordination compounds with 27Al nuclei with non-spherical coordination environments by using Hahn-echo and/or QCPMG pulse sequences. 27Al quadrupolar coupling constants (CQ( 27Al)) as large as 48.2(1) MHz. X-ray data and theoretical calculations are utilized to examine the relationships between the quadrupolar interactions and molecular structure.
Solid-state 63/65Cu NMR experiments were conducted on a series of inorganic and organometallic copper(I) complexes with a variety of spherically asymmetric Cu coordination environments. Enormous CQ(63/65Cu) values and significant copper chemical shielding anisotropies (CSAs) are measured ranging from 3.4 to 71.0 MHz. 1H-31P CP/MAS NMR spectra for complexes with 63/65Cu-31P spin pairs are used to determining the sign of CQ and EFG tensor orientation. X-ray data and theoretical calculations aid in examining the relationship of the NMR interaction tensor with the molecular structure.
Multinuclear solid-state NMR and EPR spectroscopy and first principles calculations are used to examine the electronic structures of the redox series [Pt(tfd)2]z-[NEt 4]z+ (tfd = S2C 2(CF3)2; z = 0, 1, 2). 195Pt NMR experiments revealed large 195Pt CSAs with distinct CS tensor orientations for the diamagnetic species (z = 0, 2), despite having similar structures. [Pt(tfd)2] [NEt 4] is examined using EPR, 13C and 19F MAS NMR spectroscopy. The unpaired electron spin densities at 13C and 19F nuclei were measured using variable temperature NMR experiments. Theoretical calculations help rationalize the large platinum CSAs and different CS tensor orientations and determine the electron spin densities at 13C and 19F nuclei.
The use of microcoils and WURST pulses for acquiring UWNMR spectra is explored. UW spectra can be acquired without changing the transmitter frequency using large rf fields or frequency-swept pulses. The efficiency of UWNMR spectroscopy improved for both microcoil and WURST pulse experiments compared to 4.0 mm coil experiments. Microcoils are also used to acquire UW spectra of an unreceptive nucleus (91Zr) and a spectrum comprised of both central and satellite transitions (59Co).
Tang, Joel A., "Ultra-wideline solid-state NMR spectroscopy and its application in characterizing inorganic and organometallic complexes" (2008). Electronic Theses and Dissertations. 8009.