Solid‐state NMR spectroscopy of Pb‐rich apatite

Abstract

Pb-containing hydroxylapatite phases synthesized under aqueous conditions were investigated by X-ray diffraction and solid-state nuclear magnetic resonance (NMR) techniques to determine the Pb, Ca distribution. 31P and 1H magic-angle spinning (MAS) NMR results indicate slight shifts of the isotropic chemical shift with increased Ca content and complex lineshapes at compositions with near equal amounts of Ca and Pb. 31P{207Pb} and 1H{207Pb} rotational-echo double resonance (REDOR) results for intermediate compositions show that resolved spectral features cannot be assigned simply in terms of local Ca, Pb configurations or coexisting phases. 207Pb MAS NMR spectra are easily obtained for these materials and contain well-resolved resonances for crystallographically unique A1 and A2 Pb sites. Splitting of the A1 and A2 207Pb resonances for pure hydroxyl-pyromorphite (Pb10(PO4)6(OH)2) compared to natural pyromorphite (Pb5(PO4)3Cl) suggests symmetry reduced from hexagonal. We find that 207Pb{1H} CP/MAS NMR is impractical in Pb-rich hydroxylapatites due to fast 207Pb relaxation.

Applications of nuclear shielding

“…207 Pb{ 1 H} CP/MAS NMR is impractical in Pb-rich hydroxylapatites due to fast 207 Pb relaxation. 287 2.15 Group 15 ( 14,15 N, 31 288 The combined use of two-dimensional NMR correlation experiments and gauge including AO density functional theory in 13 C NMR chemical shift calculations allows reliable and simple structural determination of regioisomeric heterocyclic systems that originate from the reactions of acylquinolinones with substituted hydrazines. Moreover, the results of differential analysis between the calculated 15 N NMR chemical shifts for hypothetical structures and the experimental data of the title azaheterocyclic systems are even more advantageous with respect to 13 C because there is no need for correlational analysis: structures of the regioisomeric compounds can be determined just by direct comparison.…”

“…31 P and 1 H magic-angle spinning (MAS) NMR results indicate slight shifts of the isotropic chemical shift with increased Ca content and complex lineshapes at components with near equal amounts of Ca and Pb. 409 The influence of the environment in which the Graham's salt is usually placed on its degradation into smaller particles was studied by 31 P NMR spectroscopy at several temperatures on solutions with 7% of Graham's salt in sodium silicate with Rw = 1.6, 2.0, 3.3, in sodium carbonate 0.15 M, in sodium hydroxide 0.10 M and 1.0 M and in water. 410 Potential metal interactions with the cleavage site of a minimal hammerhead ribozyme (mHHRz) are probed using 31 P NMR-detected Cd 2 þ titration studies of HHRz constructs containing a phosphorothioate (PS) modification at the cleavage site.…”

Structure Elucidation of an Yttrium Diethyldithiocarbamato‐Phenanthroline Complex by X‐ray Crystallography, Solid‐State NMR, and ab‐initio Quantum Chemical Calculations

“…where |δ zz -δ iso | ≥ |δ xx -δ iso | ≥ |δ yy -δ iso | [67] (i.e., δ zz is the principal component farthest from δ iso and δ yy is the component closest to δ iso ).…”

3,5‐Dimethylpyrazolyl‐Substituted Di‐ and Trisiloxanes

“…This assignment was then confirmed by the agreement of the principal components of the CSA tensors of the three Si atoms extracted from the spinningsideband spectra and the corresponding data predicted by computational methods (Table 4 and Figure S3). [19,20] The signal at δ = -63.4 ppm is easily related to Si3 in the crystal structure, which is the only four-coordinate silicon atom. Taking into account the results of the quantum chemical calculations [B3PW91/6-311+G(2d,p), calculated with the coordinates of the crystal structure], the other two peaks can now be assigned to Si1 (OSiCl 2 pz*, -123.8 ppm) and Si2 (O 2 Sipz* 2 , -135.2 ppm).…”

“…Figure 5. Orientation of the CSA tensor principal components (calculated) in 7 (Herzfeld-Berger convention); [19][20][21] from top to bottom: Si1, Si2, Si3. The arrows show only the direction not the magnitude.…”