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

Abstract

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 ³¹P nucleus in this supramolecular arrangement is used in order to develop alternative analytical method to get information on supra-molecular assemblies. ³¹P 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 ³¹P MAS NMR spectrum.