Chemical shift correlations in disordered solids

Triple-quantum correlation NMR experiments in solids using J-couplings

We show that triple-quantum-single-quantum (TQ-SQ) correlation spectra of crystalline and disordered solids can be obtained under MAS using pulse sequences based on through-bond J-couplings. The feasibility of the experiments in coupled spin-1/2 systems is demonstrated for fully 13C-labelled L-alanine and Pb3P4O13 crystalline compounds, considered as model three-spin and four-spin systems, respectively. In the case of phosphate glasses, we show that the obtained TQ-SQ correlation spectra provide an improved description of the glass forming network connectivities and of the chain length distribution in the disordered network.

NMR Heteronuclear Correlation between Quadrupolar Nuclei in Solids

We show for the first time that it is possible to acquire high-resolution heteronuclear NMR correlation experiments in solid state between second-order-broadened half integer quadrupolar nuclei (i.e., 27Al and 17O) using the scalar J-coupling. The sensitivity of the experiment is dramatically improved at high fields (gain proportional to the fourth power of the principal field) with a combination of signal enhancement techniques. This turns a challenging experiment into a real tool. We apply this experiment to characterize a calcium aluminate glass in which we prove the presence of tricluster mu3 oxygen sites and describe the signature of their directly bonded aluminum sites. Applications involve a large range of possible pairs of quadrupolar nuclei in different materials, such as glasses, porous or mesoporous framework materials, zeolites, hybrid organic-inorganic, and bioinvolved materials.