P-31 and C-13 chemical shielding tensors in the phosphoenolpyruvate moietyfrom rotary resonance recoupling C-13 and P-31 MAS and single crystal P-31NMR
M. Bechmann et al., P-31 and C-13 chemical shielding tensors in the phosphoenolpyruvate moietyfrom rotary resonance recoupling C-13 and P-31 MAS and single crystal P-31NMR, MOLEC PHYS, 98(9), 2000, pp. 605-617
A P-31 and C-13 NMR study of powder and single crystal samples of two phosp
hoenolpyruvate (PEP) compounds, the tris-ammonium salt monohydrate (NH4)(3)
(PEP). H2O (1), and the mono-ammonium-salt (NH4)(H2PEP) (2) is presented. T
he P-31 chemical shielding tensors in 1 are measured by P-31 single crystal
NMR on four minuscule samples and assigned without ambiguity by exploiting
the orientation-dependent P-31-P-31 dipolar splittings of the resonance li
nes. The orientation of the P-31 chemical shielding tensor is discussed in
terms of the C-2v- and C-3-type distortions of the phosphate PO4-coordinati
on sphere. From C-13 MAS NMR experiments with 31P rotary resonance recoupli
ng on polycrystalline powder samples the orientations of the P-31 chemical
shielding tensors in 1 and 2 are obtained, for 1 in very good agreement wit
h the P-31 single crystal NMR results. Only some of the orientational param
eters of the three C-13 chemical shielding tensors in the PEP moiety of 1 c
ould be derived from C-13 MAS NMR experiments with P-31 rotary resonance re
coupling.