Insights from across the periodic table into NMR chemical shift, electric field gradient, and spin-spin coupling tensors: New information from solid-state NMR and computational chemistry.
Date
2002
Authors
Bryce, David Lawson.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
To properly interpret the information available from nuclear magnetic resonance (NMR) parameters, it is advantageous to study the complete second-rank interaction tensors, i.e., chemical shift (CS), indirect nuclear spin-spin coupling (J), and electric field gradient (EFG) tensors. Two distinct courses of research based on a combined experimental and theoretical approach have been followed.
Modern solid-state NMR techniques have been applied to several quadrupolar nuclei to characterize the magnitude and orientations of their EFG and CS tensors. Results have been obtained for 11B, 35/37Cl, 53Cr, and 95Mo at magnetic fields of 4.7 to 18.8 T. The first measurement of a boron CS tensor is reported and interpreted in terms of a simple MO picture. Chlorine NMR of organic hydrochlorides reveals a correlation between the chlorine EFG tensor and the local hydrogen bonding environment. The first 53Cr NMR spectra of diamagnetic solids are presented and analyzed. Mo-95 NMR results provide an example of the relationship between the local molecular and electronic structure and the molybdenum CS and EFG tensors. Ab initio and density-functional theory (DFT) calculations have been employed to complement the experimental data.
The second aspect of the research involves the application of recent advances in the calculation of J via multiconfigurational SCF and relativistic DFT methods. Calculations on several diatomics for which highly precise experimental data exist from high-resolution molecular beam spectroscopy have helped to elucidate the connection between J and rotational hyperfine parameters. This connection has been exploited to establish the accuracy of the computational methods and to develop a more complete understanding of periodic trends in J coupling. This work illustrates the importance of various mechanisms which contribute to J. New insight into the phenomenon of J coupling between heavy nuclei across hydrogen bonds has been gained. The first experimental attempts to measure the antisymmetric part of J are reported.
Thesis (Ph.D.)--Dalhousie University (Canada), 2002.
Modern solid-state NMR techniques have been applied to several quadrupolar nuclei to characterize the magnitude and orientations of their EFG and CS tensors. Results have been obtained for 11B, 35/37Cl, 53Cr, and 95Mo at magnetic fields of 4.7 to 18.8 T. The first measurement of a boron CS tensor is reported and interpreted in terms of a simple MO picture. Chlorine NMR of organic hydrochlorides reveals a correlation between the chlorine EFG tensor and the local hydrogen bonding environment. The first 53Cr NMR spectra of diamagnetic solids are presented and analyzed. Mo-95 NMR results provide an example of the relationship between the local molecular and electronic structure and the molybdenum CS and EFG tensors. Ab initio and density-functional theory (DFT) calculations have been employed to complement the experimental data.
The second aspect of the research involves the application of recent advances in the calculation of J via multiconfigurational SCF and relativistic DFT methods. Calculations on several diatomics for which highly precise experimental data exist from high-resolution molecular beam spectroscopy have helped to elucidate the connection between J and rotational hyperfine parameters. This connection has been exploited to establish the accuracy of the computational methods and to develop a more complete understanding of periodic trends in J coupling. This work illustrates the importance of various mechanisms which contribute to J. New insight into the phenomenon of J coupling between heavy nuclei across hydrogen bonds has been gained. The first experimental attempts to measure the antisymmetric part of J are reported.
Thesis (Ph.D.)--Dalhousie University (Canada), 2002.
Keywords
Chemistry, Analytical.