Solid-state (25)Mg magic angle spinning nuclear magnetic resonance (MAS NMR) data are reported from a range of organic and inorganic magnesium-oxyanion compounds at natural abundance. To constrain the determination of the NMR interaction parameters (delta(iso), chi(Q), eta(Q)) data have been collected at three external magnetic fields (11.7, 14.1 and 18.8 T). Corresponding NMR parameters have also been calculated by using density functional theory (DFT) methods using the GIPAW approach, with good correlations being established between experimental and calculated values of both chi(Q) and delta(iso). These correlations demonstrate that the (25)Mg NMR parameters are very sensitive to the structure, with small changes in the local Mg(2+) environment and the overall hydration state profoundly affecting the observed spectra. The observations suggest that (25)Mg NMR spectroscopy is a potentially potent probe for addressing some key problems in inorganic materials and of metal centres in biologically relevant molecules.

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Peat char samples produced by heat treatments under an inert atmosphere of nitrogen were characterized through 13 C solid-state NMR, allowing the achievement of a detailed picture of the mechanism of carbonization. The treatments were realized at temperatures between 200 and 1000°C, with a controlled heating rate and residence time. NMR spectra were obtained in a home-built spectrometer operating at a field of 2.0 T with the use of high-resolution techniques. The results showed the steps followed during the carbonization process. Initially we observed a degradation of the natural material, with preferential loss of carbohydrates and carboxylic groups. From a heat-treatment temperature of about 500°C upward, the spectra were nearly constituted of only one resonance line with a chemical shift of about 130 ppm (from TMS), typical of aromatic structures. For the most severely treated samples, a decrease in the chemical shift of the resonance line was observed, indicating a deshielding associated with the increase in the electrical conductivity of the material. The structure of these samples was identified as consisting of planes of sp 2 carbon atoms, with a chemical environment similar to graphitic materials but with no long-range spatial order.