Alexandra Faucher

267 Pages·2016·8.3 MB·English

NMR Spectroscopy of Exotic Quadrupolar Nuclei in Solids

by

Alexandra Faucher

A thesis submitted in partial fulfillment of the requirements for the degree of

Doctor of Philosophy

Department of Chemistry
University of Alberta

© Alexandra Faucher, 2016
Abstract
This thesis is concerned with NMR studies of solids containing NMR-active quadrupolar
nuclei typically overlooked due to their unfavorable NMR properties, particularly moderate to
large nuclear electric quadrupole moments. It is shown that 75As, 87Sr, and 121/123Sb NMR
spectra of a wide range of solid materials can be obtained. Traditional 1D pulse sequences (e.g.,
Bloch pulse, spin echo, QCPMG) are used alongside new methods (e.g., WURST echo,
WURST-QCPMG) to acquire the NMR spectra; the advantages of these new methods are
illustrated. Most of these NMR spectra were acquired at an external magnetic field strength of
B = 21.14 T. Central transition (m = 1/2 to −1/2) linewidths of half-integer quadrupolar nuclei
0 I
of up to a breadth of ca. 32 MHz are obtained at B = 21.14 T, demonstrating that nuclear sites
0
with large nuclear quadrupolar coupling constants can be characterized. Many of the NMR
spectra contained in this research depict situations in which the nuclear quadrupolar interaction is
on the order of or exceeds the magnitude of the Zeeman interaction, thus rendering the high-field
approximation invalid and requiring exact treatment in which the full Zeeman-quadrupolar
Hamiltonian is diagonalized in order to properly simulate the NMR spectra and extract NMR
parameters. It is also shown that both direct (R ) and indirect (J) spin-spin coupling between
eff
quadrupolar nuclei can be quantified in some circumstances, and that the signs of the isotropic
indirect spin-spin coupling and the nuclear quadrupolar coupling constants can be obtained
experimentally in cases of high-field approximation breakdown. This research represents a
relatively large and valuable contribution to the available 75As, 87Sr, and 121/123Sb NMR data in
the literature. For example, experimentally determined chemical shift anisotropy is reported for
the 87Sr nucleus in a powdered solid for the first time, and the NMR parameters for 11B-75As
spin-spin coupling constants reported here add to a sparse collection of information on
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quadrupolar spin-pairs. Overall, this research is a step towards the goal of utilizing the entire
NMR periodic table for the characterization of molecular and crystallographic structure as well
as structural dynamics.

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Preface
This thesis is an original work by Alexandra Faucher.

Chapter 3 of this thesis has been reprinted with permission from Faucher, A.; Terskikh, V. V.;
Wasylishen, R. E. Assessing distortion of the AF − (A = As, Sb) octahedra in solid
6
hexafluorometallates(V) via NMR spectroscopy. Can. J. Chem. 2015, 93, 938-944.

Chapter 4 of this thesis has been reprinted with permission from Faucher, A.; Terskikh, V. V.;
Wasylishen, R. E. Feasibility of arsenic and antimony NMR spectroscopy in solids: An
investigation of some group 15 compounds. Solid State Nucl. Magn. Reson. 2014, 61-62, 54-61.
Copyright 2014 Elsevier.

Chapter 5 of this thesis has been reprinted with permission from Faucher, A.; Terskikh, V. V.;
Wasylishen, R. E. Spin-spin coupling between quadrupolar nuclei in solids: 11B-75As spin pairs
in Lewis acid-base adducts. J. Phys. Chem. A. 2015, 119, 6949-6960. Copyright 2015 American
Chemical Society.

For the above publications, I acquired all NMR data at B = 7.05 and 11.75 T. Some of the 75As
0
and 121/123Sb NMR experiments performed at B = 21.14 T were also performed by me during my
0
visits to the National Ultrahigh-Field NMR Facility for Solids in Ottawa, ON, Canada. The
majority of the NMR spectra acquired at B = 21.14 T were collected by Victor V. Terskikh, the
0
manager of our ultrahigh-field NMR facility. Data analysis was made by me, with the exception
of the variable temperature NMR spectra acquired at B = 21.14 T shown in Chapter 3 and the
0
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75As NMR spectrum of arsenobetaine bromide shown in Chapter 4. I have prepared all of the
above manuscripts for publication.

Chapter 6 of this thesis has been reprinted with permission from Faucher, A.; Terskikh, V. V.;
Ye, E.; Bernard, G. M.; Wasylishen, R. E. Solid-State 87Sr NMR Spectroscopy at Natural
Abundance and High Magnetic Field Strength. J. Phys. Chem. A, 2015, 119, 11847-11861.
Copyright 2015 American Chemical Society. Data were collected for this project by each listed
author, analysis of the data was made by Victor V. Terskikh, Eric Ye, and myself, and I prepared
the manuscript for publication.

The published abstracts for these articles have been used in Chapter 1 as a summary of each
project.

Minor details (e.g., symbols) have been modified from their original published appearance for
the sake of consistency throughout this thesis.

v
To my family

narrow broad is beautiful
2.0 0.0 -2.0 -4.0 MHz

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Acknowledgements
I would like to acknowledge Rod Wasylishen for giving me the opportunity to study
solid-state NMR spectroscopy in his laboratory. Rod’s encouragement, enthusiasm, and
dedication to scientific rigor were a large part of what made working in this lab so enjoyable. I
thank him for his guidance and support throughout my studies at the University of Alberta.
I would like to thank my supervisory committee, Alex Brown and Jonathan Veinot, for
inspiring and assisting me throughout my studies. I also thank Rob Schurko and Nils Petersen
for serving on my Ph.D. examination committee.
I thank all of the present and former members of the Wasylishen group. Specifically, I
thank Tom Nakashima and Kris Harris for their guidance during my early days in the group, and
Guy Bernard for his much-appreciated assistance over the years. I owe a huge thank you to my
office-mate and friend, Rosha Teymoori, for keeping me sane over the last few years.
My studies here would not have been possible without the help of the support staff and
facilities in our Department. I am incredibly grateful to Mark Miskolzie, Ryan McKay, and
Nupur Dabral for their training, troubleshooting assistance, and helpful conversations. I would
also like to thank Mark for taking the time to teach me many things about NMR spectrometer
maintenance. I thank Dieter Starke and Allan Chilton for their time/assistance fixing electronics
and other equipment, Robert McDonald and Stanislav Stoyko for their assistance in X-ray
crystallography, and Wayne Moffat for many other analytical services.
Klaus Eichele and David Bryce are thanked for the development and maintenance of
NMR simulation programs WSolids and QUEST, without which this work could not have been
completed. Frédéric Perras is thanked for writing QUEST and providing me with the program
used to simulate the RDC NMR spectra in Chapter 5. I also thank Victor Terskikh at the
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National Ultrahigh-field NMR Facility for Solids in Ottawa, ON, Canada. Victor is thanked for
acquiring and analyzing some of the spectra contained in this work, as well as for training and
supervising me during my visits to the facility.
I am grateful to my friends and family for their love and support. Specifically, I thank
Julia, Don, and Christina Palech, Bryan Faucher, and Christine Newlands. A special thanks goes
to my dad for frequently reminding me why not to eat expired dip.* Thank you for all of the
wonderful nights of board games, wine, and delicious food. I love you all!

* “I am sure your food poisoning was from that chip dip dated Feb 5 as I was pretty sick after
eating some from that container last night!” – Don Palech, February 26, 2012
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Table of Contents
1 Introduction 1
1.1 Background and Motivation 1
1.2 Overview of Projects 4
1.2.1 Assessing Distortion of the AF − (A = As, Sb) Octahedra in Solid 4
6
Hexafluorometallates(V) via NMR Spectroscopy
1.2.2 Feasibility of Arsenic and Antimony NMR Spectroscopy in Solids: 5
An Investigation of Some Group 15 Compounds
1.2.3 Spin-spin Coupling Between Quadrupolar Nuclei in Solids: 11B- 6
75As Spin Pairs in Lewis Acid-Base Adducts
1.2.4 Solid-State 87Sr NMR Spectroscopy at Natural Abundance and 7
High Magnetic Field Strength

2 Theoretical Background 8
2.1 Nuclear Spin Angular Momentum 8
2.1.1 Classical Angular Momentum 8
2.1.2 Quantum (Orbital) Angular Momentum 9
2.1.3 Quantum Spin Angular Momentum 10
2.1.4 Origin of Nuclear Spin Number 11
2.1.5 Nuclear Magnetic Moments and the Gyromagnetic Ratio 12
2.2 The NMR Hamiltonian 13
2.2.1 The Zeeman Interaction 16
2.2.2 The Boltzmann Distribution and the Net Magnetization 18
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2.2.3 Radiofrequency Pulses 19
2.2.4 Magnetic Shielding and Chemical Shift 22
2.2.5 Direct Dipolar Coupling 25
2.2.6 Indirect Spin-Spin Coupling 27
2.2.7 Quadrupolar Interaction 27
2.2.8 Exact Calculations for Large Quadrupolar Interactions 34
2.3 Nuclear Relaxation 35
2.4 The Fourier Transform 38
2.5 Experimental NMR Techniques 40
2.5.1 Magic Angle Spinning (MAS) 40
2.5.2 Spin Echo 41
2.5.3 QCPMG 41
2.5.4 WURST 42
2.5.5 WURST-QCPMG 44
2.5.6 Acquiring Ultrawideline NMR Spectra 44
2.5.7 Assembling Ultrawideline NMR Spectra 45
2.5.8 Computational Methods 46
2.5.8.1 Amsterdam Density Functional (ADF) 46
2.5.8.2 Cambridge Serial Total Energy Package (CASTEP) 46

3 Assessing Distortion of the AF − (A = As, Sb) Octahedra in Solid 48
6
Hexafluorometallates(V) via NMR Spectroscopy
3.1 Introduction 48
x