Structure elucidation of a novel aluminum methylphosphonate, Al3(CH3PO3)2•O•(OH)3, through a combination of X-ray powder diffraction, solid-state NMR spectroscopy, and computational energy minimization

A novel aluminum methylphosphonate, formula Al-3(CH3PO3)(2).O.(OH)(3), has been prepared hydrothermally. Its structure was solved by a combination of 1-D MAS NMR and 2-D five-quantum MAS NMR spectroscopies, computational energy minimization using density functional theory (DFT), and direct methods crystallographic programs tailored to X-ray powder diffraction. The structure, which crystallizes in Pmnb [a = 19.7105(1) Angstrom, b = 10.1385(5) Angstrom, c = 5.1408(3) Angstrom], is made up of aluminophosphonate layers lined on both sides with methyl groups. Aluminum adopts two crystallographic sites in the structure, which exhibit octahedral and distorted trigonal bipyramidal geometries. These give characteristic NMR signals (delta(iso) = 10.8 and 3.1 ppm, respectively), and their environment is accurately simulated by computational modeling.