NMR Spectroscopy Using Liquid Crystal Solvents (eBook)

Front Cover 1
NMR Spectroscopy using Liquid Crystal Solvents 4
Copyright Page 5
Table of Contents 6
Preface 14
Acknowledgements 16
Chapter 1. Liquid Crystals 18
1.1 Introduction 18
1.2 Classification of mesophases 19
1.3 Effect of magnetic fields on liquid crystals 27
1.4 Quantitative description of liquid crystals ordered by a magnetic field 28
1.5 Nuclear resonance spectra of solutes dissolved in liquid crystals 32
References 39
Chapter 2. The Nuclear Spin Hamiltonian for Partially Oriented Molecules 42
2.1 Introduction 42
2.2 The Zeeman term 43
2.3 Indirect spin-spin coupling 44
2.4 Dipolar coupling 45
2.5 Nuclear quadrupole interaction 48
2.6 Total anisotropic spin-spin coupling 50
References 50
Chapter 3. Analysis of NMR Spectra of Partially Oriented Molecules 51
3.1 Introduction 51
3.2 Magnetic equivalence 51
3.3 Classification of spin systems 54
3.4 Spin systems having analytical solutions 55
3.5 Analysis of spin systems using the X approximation 86
3.6 Computer analysis 92
3.7 Multiple solutions 93
3.8 Errors on parameters determined from computer analysis 95
References 101
Chapter 4. Determination of the Structure of Rigid Molecules 103
4.1 Introduction 103
4.2 Relationship between dipolar coupling constants and structure 104
4.3 Vibrational averaging 112
4.4 Examples of r2 structures determined by NMR 118
4.5 Effect of the liquid crystal phase on the structure of solutes 132
4.6 Molecular complexes 146
4.7 Computational methods 148
4.8 Survey of results 151
References 167
Chapter 5. Studies of Internal Motion 175
5.1 Introduction 175
5.2 Averaging of dipolar couplings 175
5.3 Determination of barrier heights 184
5.4 Comparison between structures determined by NMR and microwave spectroscopy for a molecule with internal rotation 193
5.5 Averaging of dipolar couplings over ring puckering motion 199
5.6 Valence isomerisation 199
5.7 Survey of results 208
References 232
Chapter 6. NMR Spectra from Quadrupolar Nuclei 239
6.1 Introduction 239
6.2 Spectra of nuclei with I = 1 240
6.3 Relationship between q and components of q in a molecule-fixed axis system 252
6.4 Determination of quadrupole coupling constants 253
6.5 Survey of results 260
6.6 Determination of orientation from quadrupole coupling constants 266
References 272
Chapter 7. Anisotropy in Nuclear Spin–Spin Coupling 275
7.1 Introduction 275
7.2 Theory of spin–spin coupling 275
7.3 Experimental determination of J 282
7.4 Survey of experimental results and theoretical calculations 292
References 299
Chapter 8. Anisotropy in Chemical Shifts 302
8.1 Introduction 302
8.2 Theory 302
8.3 Experimental methods of measuring chemical shift anisotropy 305
8.4 Survey of results 316
References 329
Chapter 9. Rotation of Nematic Samples 334
9.1 Introduction 334
9.2 Theory 334
9.3 Separation of anisotropic from isotropic interactions by sample rotation 344
References 350
Chapter 10. Nuclear Magnetic Double Resonance 352
10.1 Introduction 352
10.2 Theory 352
10.3 Spin-tickling and INDOR 356
10.4 Spin decoupling 364
References 372
Appendix: Recent publications not included in the text 374
Index 376