Solid-State NMR Investigations of Zn and Al Nuclei in Zinc-Amino Acid Complexes, Zinc-Insulin ...

295 Pages·2010·5.78 MB·English

Solid-State NMR Investigations of
67 27
Zn and Al Nuclei in Zinc-Amino
Acid Complexes, Zinc-Insulin
Hexamers, and Aluminum-Centered
Dyes
by
Kamal Mroue
A thesis
presented to the University of Waterloo
in fulfillment of the
thesis requirement for the degree of
Doctor of Philosophy
in
Chemistry
Waterloo, Ontario, Canada, 2010
c Kamal Mroue 2010
(cid:13)
I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis,
including any required final revisions, as accepted by my examiners.
I understand that my thesis may be made electronically available to the public.
ii
Abstract
Modern solid-state nuclear magnetic resonance (NMR) methodologies are applied to inves-
tigate two spin-5 nuclei, 67Zn and 27Al, in different coordination environments in order to
2
characterize the magnitudes and orientations of their electric field gradient (EFG) and nu-
clear magnetic shielding tensors. The advantages of using high (21.1T) applied magnetic
fields for detecting 67Zn directly at ambient temperatures, using the quadrupolar Carr-
Purcell Meiboom-Gill (QCPMG) pulse sequence and the stepped-frequency technique, are
demonstrated by the successful investigation of the different zinc sites in several zinc-amino
acid coordination compounds, and in the more complex polymorphs of the zinc-insulin
hexamers. In all systems, the high-field 67Zn NMR spectra are dominated only by the
quadrupolar interaction. The first two 67Zn NMR spectra of pentacoordinated zinc sites
are reported and analyzed. The experimental results are corroborated by ab initio and
density functional theory (DFT) calculations of the 67Zn NMR parameters in order to gain
better understanding of the zinc local electronic environments.
Solid-state 27Al NMR is applied to study three commercial aluminum-phthalocyanine
dyes. Solid-state27AlNMRexperiments,includingmultiple-quantummagic-angle-spinning
(MQMAS) and quadrupolar Carr-Purcell Meiboom-Gill (QCPMG), are employed at mul-
tiple high magnetic field strengths (11.7, 14.1 and 21.1 T) to determine the composition
and number of aluminum distinct sites in these dyes. The quadrupolar parameters for each
27Al site are determined from spectral simulations, with quadrupolar coupling constants
(C ) ranging from 5.40 to 10.0 MHz and asymmetry parameters (η ) ranging from 0.10
Q Q
to 0.50, and compare well with the results of quantum chemical calculations of these ten-
sors. The largest 27Al chemical shielding anisotropy (CSA), with a span of 120 10 ppm,
±
observed directly in a solid material is also reported. The combination of MQMAS and
iii
computational chemistry are used to interpret the presence of multiple aluminum sites in
two of the three samples.
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Acknowledgements
In his most famous book The Alchemist, the Brazilian author Paulo Coelho reveals the
central theme through a phrase said by the old man, King Melchizedek, to the young
shepherd Santiago:“When you want something, all the universe conspires in helping you
to achieve it.” I believe this with all my heart!
There are lots of people in my universe, who have helped me reach this point of my
life, to whom I owe my deepest thanks and gratitude for a huge variety of reasons.
I begin by saying that I could not have imagined having a better supervisor and advisor
for my graduate studies than Dr. Bill Power; without Bill’s knowledge, perceptiveness,
enthusiasm, and encouragement this thesis would never have seen the light. I specially
thank Bill for his incredible patience with my imperfections and with my continuous delays
in completing many jobs, for always keeping the door to his office open for questions, and
for his generous support that allowed me to reach this point. Thank You for everything
Bill.
Next, my thanks are due to my PhD committee members, Dr. Glenn Penner, Dr.
Marcel Nooijen, Dr. Pavle Radovanovic, and Dr. Raymond Laflamme (internal-external)
for managing to read the whole thesis so thoroughly. I would also like to thank all the rest
of the academic and support staff of the Department of Chemistry at the University of
Waterloo (UW). My special thanks go to Cathy van Esch, the administrative coordinator
for graduate studies in Chemistry, for her help with the administrative work.
IamgratefultoMikeDitty, aformermemberofthePowerLab, forhishelpwithsetting
up the QCPMG experiment on our spectrometers. Mike’s prompt and quick showing up
whenever I asked for his assistance with complicated hardware or software problems on
the NMR spectrometers, as well as his unstinting willingness to share with me his NMR
v
knowledge and expertise, are unforgettable. Jan Venne, the outstanding NMR Facility
Manager at UW, is also thanked for giving me technical support over these years. Dr. Jalil
Assoud, an excellent X-ray crystallographer and a supportive friend of mine, is thanked
for solving and analyzing crystal structures. Much respect to present and former members
of the Power Lab: Jun Gu, Abdul-Hamid Emwas, Fernando Amador, Sam Andrey, and
Mike Chan. Sam and Mike are particularly thanked for their assistance with the syntheses
of the samples for the zinc-insulin project.
Most of the NMR spectra contained in this thesis were acquired at the National
Ultrahigh-Field NMR Facility for Solids at the NRC in Ottawa, Ontario. Having ac-
cess to the state-of-the-art 900 MHz spectrometer there was a turning point in my PhD
studies. I am very grateful to Dr. Victor Terskikh, the Facility Manager, for introducing
me to the spectrometer and for his significant assistance with the acquisition of the zinc
and aluminum spectra. Dr. Eric Ye is also thanked for his technical help.
My warm thanks go to Firas Mansour, my best friend in Waterloo, for always dragging
me out of the lab for a coffee break, and for the great times we have spent together around
his dining table enjoying one of his “most delicious” Lebanese meals. I must also thank
my friends Mustapha Makkook, Adel Fakih, and Mohamad Awad from Electrical and
Computer Engineering. Mustapha is particulary thanked for introducing me to LATEX and
helping me into its basic concepts. Adel is thanked for showing real interest in my research,
and for being patient with me talking about it. Special thanks are extended to my friends
Waseem El-Huneidi and Ahmed Magdy for their helpful suggestions on the syntheses of
my samples and for the wonderful times we had together.
I wish to express my special love and gratitude to my brother Ali and his wife Ann
for their continuous love and help, especially during the first years of my life in Canada.
Without their support, those times would have been unbearable. I am grateful to my
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other siblings Nahla, Mahmoud, Kamel, Ikmal, and Mohammad, and their families, for
rendering me the sense and the value of brotherhood. I am glad to be one of them.
I feel a deep sense of gratitude to my late father, Hussein Mrou´e, and my mother,
Mahassen, who early in my life formed a part of my educational path and taught me the
goodthingsthatreallymatterinlife. Iamwholeheartedlyindebtedtomyfatherwhonever
had the chance to gain formal education, but with his visionary thinking and persistent
will, knew the real value and importance of education. He worked very hard to provide
us with the best education, despite all the difficult and dangerous circumstances we lived
through during the Civil War in Lebanon (1975–1990). My hard work and efforts put forth
in this thesis are merely a result of all that he instilled in me over the years.
Last but surely not least, I am eternally grateful to my wife, Nesrine, for always pro-
viding me with her endless love, support, and patience during these years. Words cannot
express my gratitude and love; I could not have done this without Nesrine by my side. One
of the best life experiences that we have been living through together in the past three
years was the birth of our son Ali Daniel and our daughter Juliana, both of whom have
provided a new dimension full of joy and pleasure to our joint life.
vii
Dedication
To the memory of my father, Hussein Mrou´e (1937-2003)
To my wife, Nesrine, and my children, Ali & Juliana
viii
Table of Contents
Author’s Declaration ii
Abstract iii
Acknowledgements v
Dedication viii
Table of Contents ix
List of Tables xiii
List of Figures xvi
List of Symbols and Abbreviations xxviii
1 A General Introduction 1
1.1 Preamble . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Research Objectives and Thesis Outline . . . . . . . . . . . . . . . . . . . . 4
ix
2 NMR: Basics, Theory, and Techniques 8
2.1 NMR Spin Interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.1 The Zeeman Interaction . . . . . . . . . . . . . . . . . . . . . . . . 10
2.1.2 The Radiofrequency Interaction . . . . . . . . . . . . . . . . . . . . 13
2.1.3 The Nuclear Magnetic Shielding Interaction . . . . . . . . . . . . . 15
2.1.4 The Direct Dipolar Interaction . . . . . . . . . . . . . . . . . . . . 29
2.1.5 The Indirect Spin-Spin Interaction . . . . . . . . . . . . . . . . . . 36
2.1.6 The Spin-Rotation Interaction . . . . . . . . . . . . . . . . . . . . . 38
2.1.7 The Quadrupolar Interaction . . . . . . . . . . . . . . . . . . . . . 39
2.1.8 Euler Angles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
2.2 Typical NMR Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
2.2.1 Magic-Angle Spinning (MAS) . . . . . . . . . . . . . . . . . . . . . 57
2.2.2 Spin-Echo Techniques . . . . . . . . . . . . . . . . . . . . . . . . . 63
2.2.3 Quadrupolar Carr-Purcell Meiboom-Gill (QCPMG) Experiment . . 66
2.2.4 WURST–QCPMG Experiment . . . . . . . . . . . . . . . . . . . . 70
2.2.5 Stepped-Frequency Technique . . . . . . . . . . . . . . . . . . . . . 71
2.2.6 Quantum Chemical Computation of NMR Parameters . . . . . . . 72
3 High-Field Solid-State 67Zn NMR of Several Zinc-Amino Acid Com-
plexes 75
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
x