Efficiency of dipolar and J-derived solid-state NMR techniques for a new pair of nuclei {~(31)P,~(29)Si}. Towards the characterization of Si—O—P mesoporous materials

摘要

Solid-state NMR methods based on dipolar and J-derived experiments such as CP, MAS-J-HMQC and MAS-J-INEPT MAS have been developed in the frame of the {~(31)P,~(29)Si} spin pair. The potential of these techniques has been demonstrated using model compounds including crystalline silicophosphate phases (Si5O(PO4)6 and various SiP2O7 polymorphs). Spatial interactions as well as through-bond connectivities were established. Evaluation of isotropic ~2J_(P-O-Si) coupling constants has been established by careful analysis of the HMQC and INEPT build-up curves under fast MAS. The efficiency of the ~(31)P → ~(29)Si CP MAS experiment for the detailed characterization of Si—O—P mesoporous materials (at low temperature) was demonstrated. The incorporation of P atoms in the silica network has been proved unambiguously. Such materials could be appropriate for biocompatibility purposes.