On phosphorus chemical shift anisotropy in metal (IV) phosphates and phosphonates: A 31 P NMR experimental study

The phosphorus chemical shift anisotropies, ³¹ PΔcs, and asymmetry parameters η were measured by the ³¹ P{¹ H} NMR experiments in static and low-frequency spinning samples of the zirconium phosphates and phosphonates and also in the mixed Zr (IV)/Sn (IV) phosphate/phosphonate material. The data obtained have shown a 111 connectivity in the HPO₄ and PO₃ groups, which does not change at modification and intercalation of the materials. The ³¹ PΔcs values of the phosphonate groups (43-49 ppm) significantly surpass the values characterizing the HPO₄ groups (23-37 ppm). The ³¹ P Δcs values obtained for the metal (IV) phosphates were discussed in terms of P-O distances. The ³¹ P chemical shift anisotropy parameters can help at elucidation of local structures in phosphate and phosphonate materials.

Elucidating structure and dynamics of crystalline α-zirconium phosphates intercalated with water and methanol by multinuclear solid-state MAS NMR: A comprehensive NMR approach

Solid-state NMR experiments on ² H, ³¹ P, ¹³ C, and ¹ H nuclei, including ³¹ P T₁ , ¹ H T₁ , and ¹ H T_1ρ measurements, as well as on the kinetics of proton-phosphorus cross-polarization have been performed to characterize the crystalline and amorphous α-zirconium phosphates, which were intercalated with D₂ O and/or CD₃ OD. The ¹³ C{¹ H} CP MAS NMR experiment performed for compound 1-CD₃ OD (Zr (HPO₄ )₂^. 0.2CD₃ OD) with carbon cross-polarization via protons of phosphate groups has provided a prove that the methanol was intercalated into the interlayer spaces of this compound. The variable-temperature ² H solid-echo MAS NMR spectra of intercalated compounds demonstrated that the methanol molecules, in contrast to the mobile water, were immobile, keeping, however, free CD₃ rotations around the C₃ -axis. It has been demonstrated that the intercalated species, D₂ O and CD₃ OD, do not affect the high-frequency motions of the phosphate groups. By utilizing local structural models that satisfy the constraints of the experimental data, it has been suggested that the immobile methanol molecules are located in the cavity between two neighboring layers of the zirconium phosphates. Thus, the present work illustrates the reliable criteria in a comprehensive NMR approach to structural and dynamic studies of such systems.

Hydronium Ions on the Surface of a Partially Hydrolyzed α-Zirconium Phosphate: Solid-State 2H and 31P MAS NMR Evidence

Characterization of the α-zirconium phosphates 1-D₂Oh and 1-D₂Oh/dr, partially hydrolyzed with D₂O, by powder X-ray diffraction, scanning electron microscopy, and multinuclear solid-state NMR techniques led to an unprecedented observation of D₃O⁺ ions located on the surface and stabilized by hydrogen bonds. These ions are formed after the surface phosphate groups have been lost.

Modification and intercalation of layered zirconium phosphates: a solid-state NMR monitoring

Several layered zirconium phosphates treated with Zr(IV) ions, modified by monomethoxy-polyethyleneglycol-monophosphate and intercalated with doxorubicin hydrochloride have been studied by solid-state MAS NMR techniques. The organic components of the phosphates have been characterized by the ¹³ C{¹ H} CP MAS NMR spectra compared with those of initial compounds. The multinuclear NMR monitoring has provided to establish structure and covalent attachment of organic/inorganic moieties to the surface and interlayer spaces of the phosphates. The MAS NMR experiments including kinetics of proton-phosphorus cross polarization have resulted in an unusual structure of zirconium phosphate 6 combining decoration of the phosphate surface by polymer units and their partial intercalation into the interlayer space. Copyright © 2016 John Wiley & Sons, Ltd.