³¹P and¹³C chemical shielding tensors in the phosphoenolpyruvate moiety from rotary resonance recoupling¹³C and³¹P MAS and single crystal³¹P NMR

Abstract

Print) 1362-3028 (Online) Journal homepage: http://www.tandfonline.com/loi/tmph20 31 P and 13 C chemical shielding tensors in the phosphoenolpyruvate moiety from rotary resonance recoupling 13 C and 31 P MAS and single crystal 31 A 31P and I3C NMR study of powder and single crystal samples of two phosphoenolpyruvate (PEP) compounds, the tris-ammonium salt monohydrate NH4)3(PEP).H20 (l), and the mono-ammonium-salt (NH4)(H,PEP) (2) is presented. The A P chemical shielding tensors in 1 are measured by 31P single crystal NMR on four minuscule samples and assigned without ambiguity by exploiting the orientation-dependent 31P-31P dipolar splittings of the resonance lines. The orientation of the 31P chemical shielding tensor is discussed in terms of the C2"-and C3-type distortions of the phosphate P04-coordination sphere. From I3C MAS NMR experiments with 31P rotary resonance recoupling on polycrystalline powder samples the orientations of the 31P chemical shielding tensors in l and 2 are obtained, for l in very good agreement with the 31P single crystal NMR results. Only some of the orientational parameters of the three 13C chemical shielding tensors in the PEP moiety of 1 could be derived from 13C MAS NMR experiments with 31P rotary resonance recoupling.

Revealing molecular self-assembly and geometry of non-covalent halogen bonding by solid-state NMR spectroscopy

“…Although these simulated lineshapes appear to reproduce the main splitting, some striking differences with respect to the experimental lineshapes are clearly visible. The incorporation of dipolar interactions between 15 N and 127 I nuclei leads to much better fits (red lines). Since there is no hint of 15 N- 15 N homonuclear recoupling at the n = 1 2 rotary resonance condition, we can exclude any contribution of this type to the observed features.…”

“…The incorporation of dipolar interactions between 15 N and 127 I nuclei leads to much better fits (red lines). Since there is no hint of 15 N- 15 N homonuclear recoupling at the n = 1 2 rotary resonance condition, we can exclude any contribution of this type to the observed features. It is also worth pointing out that the quadrupolar-dipolar cross-terms as well as the anisotropic J-couplings can be safely ignored at a static magnetic field of 9.4 T, 14a considering the intermolecular character of the halogen bond.…”

“…This must be due to the presence of Scheme 1 Synthesis of benzyl-di(4-iodobenzyl)-amine (1). two magnetically nonequivalent and crystallographically distinct 15 N sites in the unit cell. These two peaks cannot result from a residual dipolar splitting (RDS) due to a second-order quadrupolar-dipolar cross-term.…”

“…Magnitudes and relative orientations of the15 N chemical shift and 15 N-127 I dipolar coupling tensors along with corresponding internuclear N-I distances for the two distinguishable nitrogen sites in compound 1 Site Dd/Hz a Z b d NÁ Á ÁI /Hz r NÁ Á ÁI /Å a CS (1) b CS (1) I À475 AE 20 0.67 AE 0.1 127 AE 5 2.7 AE 0.04 0.0 AE 15 23.0 AE 2 II À512 AE 20 0.72 AE 0.1 100 AE 5 2.9 AE 0.05 0.0 AE 15 25.0 AE 2 The anisotropy is defined as Dd = d 33 À d iso . b The asymmetry as Z = (d 22 À d 11 )/Dd with d 11 Z d 22 Z d 33 .…”

“…11 Proton decoupling is applied throughout the evolution and acquisition periods. The evolution of the 15 N magnetization under rotary resonance is therefore determined by only two recoupled interactions: the 15 N chemical shift anisotropy (CSA) and the heteronuclear dipolar 15 N-127 I coupling. So far, the rotary resonance effect has been exploited for 13 C and 1 H CSA measurements 12,13 and for determining intramolecular dipolar interactions for 31 P-15 N, 13 C-14 N, 13 C-31 P and 31 P-113 Cd spin pairs.…”