Solid state 2H NMR measurements

Correlations between 2H quadrupole interaction parameters and hydrogen bond geometry have also been considered for situations other than 0-H---0 hydrogen bonds. For example, solid state 2H NMR spectra of 2H labelled amino acids, peptides and polypeptides were measured over a wide temperature range [74]. From spectral simulations based on dynamic 2H NMR theory, parameters such as the 2H quadrupolar coupling constant and asymmetry parameter were determined, and relationships between these NMR parameters and the hydrogen... 

While cooling, when the limit xa = 1 /, (cf. Eq. 15) is reached, the central Lorentzian NMR line, which is characteristic of a liquid (t-,8, solid-state spectrum, in the case of 2H NMR the Pake spectrum. The breadth of the solid-state spectra makes it difficult to measure the corresponding (short) free induction decay (FID), so that it is necessary to use echo-techniques (cf. Section II.D.2). Figure 38 (left) shows solid-echo 2H NMR spectra of glycerol-. The crossover from a Lorentzian line to the Pake spectrum is observed some 20% above Tg. Below Tg the spectrum is independent of temperature. In Fig. 37 (right), the corresponding 31P NMR spectra of m-tricresyl phosphate (m-TCP) are displayed. The characteristic spectral shape is now determined by the anisotropic chemical... 

Much work has also been carried out on non-cereal plant proteins. Solid-state H and 2H NMR transverse relaxation measurements were used to investigate the effect of hydration on the plasticization of vicilin, legumin, and albumin fractions from peas.81 Their behaviour indicated that the plasticization of the globular legume proteins is considerably less than that found before for the linear barley protein C-hordein. The effects of microbial transglutaminase treatment on soy protein samples have been studied by H and solid-state 13C NMR spectroscopy, and its relation to the glass transition temperature was examined.82-83... 

Solution and solid state studies of non-classical transition metal hydride systems have revealed fast intramolecular motions of the dihydrogen ligands [7, 8]. These motions represent a rotational diffusion around the axis perpendicular to the H-H (or D-D) vector (Scheme 1), a libration (Scheme 2) or 180° - jumps (Scheme 3) around the same axis [43]. It has been shown that the type of motion, its frequency and the orientation of eq z (angle a in Scheme I) affect strongly on the 2H NMR parameters, causing an elongation of the H T, time in solution [25] or a decrease of the quadrupole splitting in the solid -state H NMR spectra [22]. This influence creates additional problems for DQCC determinations from experimental relaxation measurements or solid state NMR data, particularly when the orientation of the eqzz vector is unknown. 

Solid-state NMR spectra of 2H, where the main concern is to refocus the reasonably small first-order broadening, are commonly obtained by measuring the quadrupolar echo on a static sample. In such a case, the o pq frequencies can be approximated... 

In another paper in this issue [1], the molecular motions involved in secondary transitions of many amorphous polymers of quite different chemical structures have been analysed in detail by using a large set of experimental techniques (dynamic mechanical measurements, dielectric relaxation, H, 2H and 13C solid state NMR), as well as atomistic modelling. 

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