Through-Bond Indirect and Through-Space Direct Dipolar Coupling ³¹P MAS NMR Constraints for Spectral Assignment in the Cubic 3 × 3 × 3 Superstructure of TiP₂O₇

A 31P solid-state NMR study of TiP2O7 is reported. The combined constraints from one-dimensional 31P MAS NMR experiments and from 31P 2D MAS NMR experiments probing through-bond P−O−P connectivities via homonuclear J coupling interactions (TOBSY experiments), positively identify the cubic space group Pa3̄ with a 3 × 3 × 3 superstructure. Additional 31P 2D MAS NMR experiments, probing spatial connectivities between phosphorus sites via homonuclear dipolar coupling interactions (31P single-quantum−double-quantum correlation MAS NMR experiments), subsequently lead to complete assignment of the 11 distinct crystallographic P sites in the structure of TiP2O7 to the corresponding eight resolved resonances in 31P MAS NMR spectra of TiP2O7, while 31P RIL ZQT and C7 DQT MAS NMR experiments confirm that TiP2O7 and the cubic phase of SiP2O7 are isostructural.