Magic-angle-spinning 31P NMR spectra of solid dihydrogen phosphates: Comparison of ordered and dynamically disordered compounds

✍ Scribed by Claudia M. Lagier; Alejandro C. Olivieri; David C. Apperley; Robin K. Harris

• Publisher: Elsevier Science
• Year: 1992
• Tongue: English
• Weight: 379 KB
• Volume: 1
• Category: Article
• ISSN: 0926-2040
• DOI: 10.1016/s0926-2040(10)80005-0

✦ Synopsis

High-resolution 31p NMR spectra are reported for several dihydrogen phosphates in the solid state. Shielding tensor components were retrieved by analysis of the sideband intensities. The results, together with previously published data, can be grouped according to the presence and type of proton exchange occurring in the crystals. Static MH zP04 samples (M = Na, Li) show a shielding anisotropy .dO" of -120 ppm. In the case of M = Cs (one static P-OH bond and two oxygens attached to "half' hydrogens on the average) .dO" is smaller ( -75 ppm) and can be understood in terms of the accepted, proton-exchange model. For highly disordered samples (M = K, NH 4 , Rb), where all four oxygens have nearby hydrogens with 50% occupancy, .dO" is even smaller (-30 ppm) but not zero. In the last-mentioned cases, 31 P NMR information suggests that local P0 4 environments may not have the symmetry that could be expected on the basis of the known crystal structures.