Layered metal(IV) phosphonate materials: Solid-state 1 H, 13 C, 31 P NMR spectra and NMR relaxation.

Abstract

Multinuclear solid-state NMR and powder X-ray diffraction data collected for phosphonate materials Zr(O3 PC6 H4 PO3 ) · 3.6H2 O and Sn(O3 PC6 H4 PO3 )0.85 (O3 POH)0.30 ·3.09H2 O have resulted in the layered structure, where the phosphonic acids cross-link the layers. The main structural motif (the 111 connectivity in the PO3 group) has been established by determination of chemical shift anisotropy parameters for phosphorus nuclei in the phosphonate groups. An analysis of the variable-temperature 31 PT1 measurements and the shapes of the phosphorus resonances in the 31 P static NMR spectra have resulted in the dipolar mechanism of the phosphorus spin-lattice relaxation, where the rotating phenylene rings reorient dipolar vectors P… H as a driving force of the relaxation process. It has been found that water protons do not affect the 31 PT1 times. The activation energy of the phenylene rotation in both compounds has been determined as low as 12.5kJ/mol. The interpretation of the phosphorus relaxation data has been independently confirmed by the measurements of 1 H T1 times for protons of the phenylene rings.