Chlorine, Bromine and Iodine NMR

The increasing interest in NMR spectroscopy of what in some confer­ ences in this field is commonly termed "other nuclei" is unmistakable. Chemists and biologists who employ NMR spectroscopy to study their problems have, however, been somewhat reluctant to study nuclei with electric quadrupole moments. These nuclei frequently give rise to broad NMR signals, sometimes too broad to be detectable with ordinary high resolution NMR spectrometers. Spectrometers that could cope with broad NMR signals of low intensity, "wide-line" spectrometers, have been available since the mid 1950:s but it appears that most of these instruments ended up in physical laboratories where the research was primarily directed towards solid state problems. The study of quadrupolar nuclei can provide unique and very valuable information on a variety of physico-chemical and biological systems. For one thing the relaxation of quadrupolar nuclei is in many ways easier to interpret than the relaxation of non-quadrupolar nuclei, since the former is in many cases caused by purely intramolecular interactions modulated by the molecular motion. Studies of quadrupolar relaxation have therefore furnished important information about molec­ ular reorientation and association in liquids and have played - and will certainly play for many years - an important role in testing new theoretical models of molecular motion in liquids.

Contenu

1. Introductory Aspects.- 1.1 General Properties of Halogens.- 1.2 Static Parameters.- 1.2.1 Quadrupole Splittings.- 1.2.2 Nuclear Shielding.- 1.2.3 Spin-Spin Couplings.- 1.3 Dynamic Parameters.- 1.3.1 Quadrupolar Relaxation.- 1.3.2 Other Relaxation Mechanisms.- 1.4 Chemical Exchange Effects.- 1.5 Experimental Aspects.- 2. Relaxation in Molecules or Ions With Covalently Bonded Halogens.- 2.1 Quadrupole Relaxation.- 2.1.1 General Aspects.- 2.1.2 On the Evaluation of the Correlation Time.- 2.1.3 Models for Molecular Rotation in Liquids.- 2.1.4 Survey of Experimental Results and Their Interpretation.- 2.2 Other Relaxation Mechanisms.- 3. Shielding Effects in Covalent Halogen Compounds.- 3.1 Theoretical Aspects.- 3.1.1 General Considerations.- 3.1.2 Approximate Calculations of Nuclear Shielding.- 3.1.3 Correlations Between Electronic Shielding and Quadrupolar Coupling Constants.- 3.1.4 Halide Ion Shielding in Crystals and Aqueous Solutions.- 3.2 Experimental Data.- 3.3 Medium Effects on Halogen Shielding Constants.- 3.3.1 General Considerations.- 3.3.2 Medium Effects on Chlorine Shielding Values.- 4. Scalar Spin Couplings.- 4.1 General Considerations.- 4.2 Experimental Data on Cl, Br and I Spin Couplings.- 5. Relaxation of Chloride, Bromide and Iodide Ions.- 5.1 Quadrupole Relaxation.- 5.1.1 General Aspects.- 5.1.2 Halide Ion Quadrupole Relaxation in Infinitely Dilute Aqueous Solutions.- 5.1.2.1 Experimental Results.- 5.1.2.2 Electrostatic Models.- 5.1.2.3 Electronic Distortion Model.- 5.1.3 Aqueous Solutions of Alkali Halides.- 5.1.3.1 Experimental Concentration Dependences.- 5.1.3.2 Electrostatic Model.- 5.1.3.3 Electronic Distortion Model.- 5.1.3.4 Water Isotope Effect.- 5.1.3.5 Mixed Alkali Halide Solutions.- 5.1.3.6 Temperature Dependence.- 5.1.4 Aqueous Solutions of Other Inorganic Halides.- 5.1.4.1 Hydrogen Halides.- 5.1.4.2 Ammonium Halides.- 5.1.4.3 Alkaline Earth Halides.- 5.1.4.4 Other Metal Halides.- 5.1.5 Aqueous Solutions Containing Small Hydrophobic Ions or Molecules.- 5.1.6 Halide Ions in Surfactant Systems.- 5.1.7 Halide Ions in Mixed Solvent and Non-Aqueous Solutions.- 5.2 Relaxation Rates and Chemical Shifts in Paramagnetic Systems.- 5.2.1 General Comments.- 5.2.2 Experimental Studies.- 5.3 Chemical Exchange of Halide Ions.- 5.3.1 General Considerations.- 5.3.2 Effects of Different Isotopes.- 5.3.3 Exchange Rates Accessible for Study.- 5.3.4 Ligand Exchange Mechanisms in Inorganic Halide Complexes.- 5.3.5 Experimental Studies of Halide Ion Exchange: Systems Involving Halogen Molecules.- 5.3.6 Experimental Studies of Halide Ion Exchange: Metal-Halide Complexes.- 6. Shielding of Halide Ions.- 6.1 Absolute Shielding Values of Ions in Aqueous Solutions.- 6.1.1 Theoretical Calculations of Shieldings in Alkali Halide Crystals.- 6.1.2 Estimates of Absolute Ion Shieldings from Relaxation Rates and Solvent Isotope Shifts.- 6.1.3 Molecular Beam and Atomic Beam Data.- 6.1.4 Discussion of the Absolute Shielding Values in Table 6.1.- 6.2 Shielding in Aqueous Alkali Halide Solutions.- 6.3 Shielding in Other Aqueous Solutions.- 6.4 Shielding in Mixed Solvent and Non-Aqueous Solution.- 6.5 Water Solvent Isotope Effect on Shielding.- 7. Quadrupole Splittings in Liquid Crystals.- 7.1 General Aspects on Static Quadrupole Effects of Mesomorphous Systems.- 7.2 Halogen Quadrupole Splittings of Covalent Compounds in Liquid Crystals.- 7.3 Quadrupole Splittings of Halide Ions in Amphiphilic Mesophases.- 8. Halide Ions in Biological Systems.- 8.1 General Principles.- 8.1.1 Introduction.- 8.1.2 Quadrupolar Relaxation of I = 3/2 Nuclei.- 8.1.3 Chemical Exchange of a Spin I = 3/2 Nucleus.- 8.1.4 The Influence of Chemical Exchange on the Correlation Time ?C.- 8.1.5 Effects of Internal Motion at the Macromolecular Binding Site.- 8.1.6 Halide Exchange in Multi-Site Systems.- 8.1.7 General Types of Biological Halide NMR Studies and Parameters Attainable.- 8.1.8 Evaluation of Rate Parameters.- 8.1.9 Determination of Binding Constants and Related Parameters.- 8.1.10 Competition Experiments Between Different Ligands.- 8.1.11 Evaluation of Rotational Correlation Times.- 8.2 Small Molecules or Ions of Biological Interest.- 8.3 Polypeptides.- 8.4 Proteins.- 8.4.1 Carbonic Anhydrase.- 8.4.2 Alcohol Dehydrogenase.- 8.4.3 Alkaline Phosphates.- 8.4.4 Serum Albumin.- 8.4.5 Hemoglobin.- 8.4.6 Other Proteins.- 8.5 Miscellaneous Systems.- 9. Studies of the Perchlorate Ion.- 9.1 Introduction.- 9.2 Shielding.- 9.3 Quadrupole Effects.- 10. Recent Work.- 11. References.- 12. Subject Index.