Assembly of benzene-1,3,5-tris(methylenephosphonic acid) and guanidinium salt: Single crystal-X-ray characterisation and P-31 solid state NMR investigations

The co-crystallisation of benzene-1,3,5-tris(methylenephosphonic acid) [C9H15O9P3]1 with guanidinium chloride [CH6N3]Cl, yields compound 2 that possesses the following composition [CH6N3](3) [C9H13O9P3] [C9H14O9P3]. The crystal structure of this supramolecular material, which possesses six crystallographically inequivalent phosphorus atoms, is reported. The packing of this 3D-supramolecular arrangement reveals the presence of 33 hydrogen bonds engaging the couples phosphonic acid-guanidinium and phosphonic acid-phosphonic acid. Solid-State MAS NMR of the sensitive P-31 nucleus in this supramolecular arrangement is used in order to develop alternative analytical method to get information on supra-molecular assemblies. P-31 through-space single quantum-double quantum correlation experiments have been performed leading to two possible assignments of the 6 crystallographic P sites to the corresponding resonances in the 1D P-31 MAS NMR spectrum.