Fourier transform NMR study

A Multinuclear Fourier Transform NMR Study of Perfluorosulfonate Ionomers... 

Allerhand, A. (1975). Pure and Applied Chemistry 41, 247. Natural-Abundance Carbon-13 Fourier Transform NMR Studies of Large Molecules. 

A Fourier Transform NMR Study of (Arene)tricarbonylchromium Complexes, G- M. Bodner and L. J. Todd, Inorg. Chem., 13, 360 (1974). 

The 13C NMR sensitivity can sometimes be a problem, but for the kind of samples studied here the effective concentration of monomer units is several molar which does not place excessive demands on present Fourier transform NMR spectrometers. In addition to the sensitivity of the chemical shift to structure (9), the relaxation of protonated carbons is dominated by dipole-dipole interaction with the attached proton (9). The dependence of the relaxation parameters T, or spin-lattice, and Tor spin-spin, on isotropic motional correlation time for a C-H unit is shown schematically in Figure 1. The T1 can be determined by standard pulse techniques (9), while the linewidth at half-height is often related to the T2. Another parameter which is related to the correlation time is the nuclear Overhauser enhancement factor, q. The value of this factor for 13C coupled to protons, varies from about 2 at short correlation times to 0.1 at long correlation... 

H NMR has long been routinely used to detect the presence of M-H bonds and also to obtain structural information about clusters containing organic ligands. The availability of Fourier transform NMR spectrometers over the last few years has enabled studies involving 13C, 31P and other nuclei also to be carried out. This has made NMR an extremely useful technique for obtaining structural information and, be-... 

The introduction of additional techniques such as Pulsed Fourier Transform NMR spectroscopy (PFT-NMR) has considerably increased the sensitivity of the method, allowing many magnetic nuclei which may be in low abundance, including 13C, to be studied. The additional data available from these methods allow information on polymer structure, conformation and relaxation behaviour to be obtained (1.18.20). 

D. Shaw, Fourier Transform NMR Spectroscopy, Studies in Physical and Theoretical Chemistry, Vol. 30, 2nd ed., Elsevier, Amsterdam, 1984. 

High field Fourier transform NMR (B0 = 17.6T for the study of H at 750 MHz) has considerably expanded the scope of this method, due to the speed of acquisition... 

All facets of study have been greatly aided by the ease with which crystal structures may be obtained and by the availability of sensitive Fourier transform NMR spectrometers which allow nuclei such as l70, 51V, wNb, s5Mo, and, K3W to be used for structural studies. Oxygen-17 NMR spectroscopy has proved to be particularly useful because 170 chemical shifts are very sensitive to environment. As a result it is possible to distinguish between terminal and various kinds of bridging oxygen sites. The l70 spectrum of [W Oi, ]2 and its structure are shown in Fig. Ifi-IOa/1 We see... 

The molecular weights of proteins studied thus far range from about 5000 to 15,000. The use of three-dimensional Fourier transform NMR may ultimately permit the study of macromolecules up to a molecular weight of 40.000. 

Fourier transform NMR spectroscopy, although used extensively to study 13C and 15N nuclei, has only very recently been applied to ll9Sn. (27, 35-40,42—44)... 

Recent advances in the development of non-invasive, in situ spectroscopic scanned-probe and microscopy techniques have been applied successfully to study mineral particles in aqueous suspension (Hawthorne, 1988 Hochella and White, 1990). In situ spectroscopic methods often utilise molecular probes that have diagnostic properties sensitive to changes in short-range molecular environments. At the particle-solution interface, the molecular environment around a probe species is perturbed, and the diagnostic properties of the probe, which can be either optical or magnetic, then report back on surface molecular structure. Examples of in situ probe approaches that have been used fruitfully include electron spin resonance (ESR) and nuclear magnetic resonance (NMR) spin-probe studies perturbed vibrational probe (Raman and Fourier-transform IR) studies and X-ray absorption (Hawthorne, 1988 Hochella and White, 1990 Charletand Manceau, 1993 Johnston et al., 1993). 

Any modern Fourier transform NMR spectrometer manufactured in the 1980s by major instrument companies is capable of performing various types of H NMR experiments needed for studies of hemoglobin. With a modern 7.0-Tesla high-resolution NMR spectrometer operating at 300 MHz for H, a satisfactory H NMR spectrum (with a signal-to-noise ratio of 20 or better) of 0.3—0.5 ml Hb in millimolar concentration contained in a 5-mm sample tube can be obtained in a few minutes. 

A pulsed NMR spectrometer, with a variable frequency and variable temperature facility is best suited for the study of these disordered systems.26 27 For dipolar glasses and relaxor systems, a spin echo Fourier transformation NMR spectra of the system have been measured in a wide bore superconducting magnet ( typically at 9.2 T). 

Oxygen occurs in Nature in three isotopic species 160 (99.759%), nO (0.0374%), and 180 (0.2039%). The rare isotopes, particularly lsO, can be concentrated by fractional distillation of water, and concentrates containing up to 99 at. % lsO or up to 90 at. % nO as well as other labeled compounds are commercially available. Oxygen-18 has been widely used as a tracer in studying reaction mechanisms of oxygen compounds. Oxygen-17 has a nuclear spin 5/2, but because of the low abundance of this isotope and appreciable quadrupole moment, enriched materials and Fourier transform nmr techniques are required. 

The earliest studies of Mg NMR were largely exploratory and used continuous-wave NMR technology [36-40]. In general, these studies suffered from a lack of instrumental sensitivity. Nevertheless, these exploratory studies demonstrated the ability of Mg NMR to provide information on the chemistry of complexation. One of the first applications of Fourier transform techniques to Mg-NMR was on aqueous Mg" electrolytes (e.g., MgBr2 and MgCU) [41]. Fourier transform NMR made it possible to study concentrations as low as 0.002 M in natural abundance Mg solutions in less than 12 h. 

The first application of NMR for the study of humic substances in soil was made by Neyroud and Schnitzer(7) using continuous wave NMR spectroscopy. Later, Gonzalez-Vila et al.(2) were the first to apply Fourier transform NMR for the analysis of dissolved humic substances extracted from soil. The development of... 

Early studies were made by continuous wave 119Sn NMR, and later by intemuclear 1H 119Sn double resonance (INDOR), in which a tin satellite line in the proton NMR spectrum is monitored as the region of the tin resonance frequency is simultaneously swept.41 42 Since the introduction of pulsed Fourier transform NMR, direct observation of the 119Sn resonance has become the standard technique for measurements,37> 39 some-... 

Related reviews have been published on the use of NMR in pesticide analysis ( 1), metabolic studies (2,2) drug metabolism (4,2), and medicinal cKemistry (6,7). Since nfost of these reviews as Well as many texts contain introductions to NMR, none will be presented here. Furthermore, an audio course on Fourier Transform NMR Spectroscopy is also available (8). Since structural characterization is often based on empirical correlations, we have found compilations of proton spectra by Aldrich, Sadtler, and Varian (9-11) and carbon spectra by Breitmaier et al. and Bruker (12,13) to be useful. Becker (14) has presented extensive lists oT references that contain useful compilations of NMR data (pp 77 and 106). Techniques... 

In the last years the technique of Fourier transform NMR spectroscopy has become widely appreciated for its speed and increased sensitivity it has especially become the method of choice for studies of the less sensitive nuclei, such as 13C or 15 N. In principle, the same information is contained in the slow passage and Fourier-transformed, pulse-excited spectra, and each may be optimized for resolution or for studies of particular features of the spectrum. Fourier transformation is nor-... 

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