Multinuclear magnetic resonance investigations of structure and order in borates and metal cyanides

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Aguiar, Pedro Miguel
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The local information provided by nuclear magnetic resonance (NMR) makes it an ideal method for the structural investigations of materials lacking extended long-range ordering. This work focuses on investigations of two types of materials possessing very different types of disorder. The first section involves investigations of alkali borate glasses and the application of solid-state NMR techniques to probe short- and medium-range ordering in such glasses. Differences between the various alkali borates over a wide compositional range are probed using one and two-dimensional techniques. The use of double-resonance dipolar recoupling techniques to investigate cesium-boron distances is investigated. The second section probes a series of transition-metal cyanide coordination polymers. The bidentate nature of the cyanide ligand allows for the possibility of forming numerous isomers. Information about the isomer(s) present is gained via the various NMR parameters available, such as the chemical shifts, shift anisotropies and J-couplings. This is then extended to the characterization of paramagnetic transition-metal cyanides, where strong electron-nuclear interactions are shown to significantly increase spin-lattice relaxation rates allowing the acquisition of spectra without the need of typically employed enhancement techniques, yet often yielding spectra of better quality. Variable-temperature experiments allow a measure of the electron-nuclear interaction, which can be related to spatial proximity, and provide “diamagnetic” chemical shifts allowing comparison with other cyanides. J-couplings and chemical shift anisotropies are shown to be applicable in much the same fashion as with diamagnetic systems.
Solid-State NMR, Glasses, Cyanides, MQMAS, Nuclear Waste, Magic-angle spinning
P.M. Aguiar, S. Kroeker, “Boron Speciation and Non-bridging Oxygens in High-Alkali Borate Glasses”. Journal of Non-Crystalline Solids, 353, 2007, 1834-1839
M.J. Katz, P.M. Aguiar, R.J. Batchelor, A.A. Bokov, Z-G Ye, S. Kroeker, D.B. Leznoff. “Structure and Multinuclear Solid-State NMR of a Highly Birefringent Lead-Gold Cyanide Coordination Polymer”. Journal of the American Chemical Society, 128(11), 2006, 3669–3676
L. Ouyang, P.M. Aguiar, R.J. Batchelor, S. Kroeker, D.B. Leznoff. “Preparation, Structure and Solid-State NMR Characterization of a Paramagnetic CuI/CuII/ZnII Coordination Polymer with Multiple CN-Binding Modes”. Chemical Communications, (7), 2006, 744-746
S. Kroeker, P.M. Aguiar, A. Cerquiera, J. Okoro, W. Clarida, J. Doerr, M. Olesiuk, G. Ongie, M. Affatigato and S.A. Feller. “Alkali Dependence of Tetrahedral Boron in Alkali Borate Glasses”. Physics and Chemistry of Glasses: European Journal of Glass Science and Technology Part B, 47(4), 2006, 393-396
P.M. Aguiar, S. Kroeker, “Medium-Range Order in Cesium Borate Glasses Probed by Double-Resonance NMR”. Solid-State Nuclear Magnetic Resonance, 27, 2005, 10-15
N.D. Draper, R.J. Batchelor, P.M. Aguiar, S. Kroeker, D.B. Leznoff. “Factors Affecting the Solid-State Structure and Dimensionality of Mercury Cyanide/Chloride Double Salts, and NMR Characterization of Coordination”. Inorganic Chemistry, 43, 2004, 6557-6567