Chemical Shift Of 31P Research Articles

Characterisation of commercial ionomer glasses using magic angle nuclear magnetic resonance (MAS-NMR)

Five commercial ionomer glasses (Fuji IX, Ketac Molar, G338, G2, and G2SR) used to produce glass (ionomer) polyalkenoate dental cements were studied. 29Si, 27Al, 31P and 19F magic angle spinning nuclear magnetic resonance (MAS-NMR) Spectroscopy was used to characterise the glasses and the resulting spectra compared with previous studies of model glasses. The 29Si NMR spectra were consistent with Q 4(3Al) and Q 4(4Al) units being present and agreed with the low non-bridging oxygen contents calculated from the elemental composition. The 27Al NMR spectra typically exhibited three distinct sites at 45–60, 20 and 0 ppm which have been attributed to Al(IV), Al(V) and Al(VI) coordinate aluminium. The presence of Al(V) and Al(VI) are consistent with previous studies of model ionomer glasses. The 31P spectra all exhibited a chemical shift between −8 and −23 ppm with the exception of the Ketac Molar glass, which exhibited a peak at 2–3 ppm consistent with orthophosphate. The chemical shift of 31P in the range −8 to −23 ppm indicates a PO 4 tetrahedra surrounded by 1–4 Al moieties. The 19F NMR spectra indicated the presence of Al–F–Ca( n) in the G2 and G338 glasses, Al–F–Sr( n) in the G2SR and Fuji IX glasses and crystalline CaF 2, LaF 3, Al–F–Ca( n) in the Ketac Molar glass. The G338 glass with a high non-bridging oxygen content showed the presence of a F–Ca( n) species. There was also present in all the glasses a peak corresponding to Al–F–Na( n). The intensity of this peak was approximately proportional to the sodium content.

Mixed alkali effect in a three dimensional structure NASICON

The conductivity has a minimum against ionic ratio in Na2−yAgyZr1.5Mg0.5(PO4)3 with a three dimensional network which is called as a mixed alkali effect (MAE). In this paper, we discussed23Na and31P MAS NMR spectra in MAE. The central line profiles exhibit characteristic changes due to values of asymmetry parameter η. The observed profiles are produced by the second-order quadrupole interaction with the electric field gradient. The peak intensity of side band against ionic ratio in MAS NMR spectra showed a small maximum due to the Na-Ag dipolar interaction which corresponds to the conductivity minimum. The chemical shifts of31P MAS NMR showed the strong dependence of polarizability of mobile ions that share oxygens in the PO4 tetrahedra and the ZrO6 octahedra. Their results indicate that there are some ordered structures of Na-Ag dependent on the ionic ratio in MAE.

TmDOTP5-: a substance for NMR temperature measurements in vivo.

The chemical shifts of 31P and 1H in thulium 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrakis(methylene phosphonate) (TmDOTP5-) are approximately two orders of magnitude more sensitive to temperature than are water proton and 19F shifts. In the physiologically relevant pH range, the 31P and 1H chemical shifts of TmDOTP5- are linear functions of temperature between 25 and 47 degrees C. The results indicate that using TmDOTP5- can provide measurements of temperature in vivo that are significantly more accurate than methods based on water and fluorocarbon chemical shifts.

31P Magic-angle spinning nuclear magnetic resonance spectroscopy of calcium phosphate glasses

31 P Magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy of a series of Ca phosphate glasses yields the following results and conclusions: (1) The relative concentrations of Q1, Q2, and Q3 P-tetrahedra are consistent with theoretical expectation and previous experimental work, except that near the metaphosphate composition tetrahedra with all three polymerizations are present. This increased range of polymerizations is consistent with previous work on silicate compositions. (2) The chemical shift of 31P in Q2 polymerization becomes less shielded (less negative) with increasing Ca content, parallelling the previously published results for Na phosphate glasses. (3) The chemical shifts are systematically more negative than for the Na phosphate glasses, consistent with theoretical expectation and experimental work.

Chemical shifts in the29Si NMR spectra and intramolecular reaction mechanisms in C, C-bis(trimethylsilyl)phosphaalkenes

The changes in the chemical shifts of31P,13C, and29Si nuclei in structurally similar phosphaalkenes of the series XiP = C(SiMe3)2 have been investigated. The specific influence of the electrons of each of the four groups of substituents Xi on the delocalized π-system −P = C(SiE, SiZ) has been revealed. When the effect of conjugation (or hyperconjugation) from Xi is strengthened, the screening of the SiZ atom increases as the SiE atom loses its screening. In the case of Xi with a predominant inductive effect (halogens, uncojugated groupings) the changes in the screening of SiZ and SiE are symbatic. The correlations of the chemical shifts δa with Hammett's σ-constants and the behavior of the ionization potentials of the ν-and np energy levels in these compounds are discussed. It is assumed that the asymmetry in the degree of screening of the SiE and SiZ atoms is related to the participation of the unshared electron air of the P atom in the reaction with the −C(SiMe3)2 groupings.

Combination of 31P-NMR magnetization transfer and radioisotope exchange methods for assessment of an enzyme reaction mechanism: rate-determining steps of the creatine kinase reaction

The theoretical analysis of a reversible enzyme reaction performed in this work shows that the 31P-NMR magnetization (saturation) transfer technique combined with a radioisotope exchange method may potentially provide information on the position of rate-determining step(s). It depends on chemical shifts of NMR signals of nuclei of interest in free and enzyme-bound forms of substrate(s) and product(s) of the reaction. The creatine kinase reaction ( MgATP + creatine ▪ MgADP + P-creatine ) has been used as a model. Chemical shifts of 31P in binary, ternary and transitional state substrate-enzyme complexes have been estimated by the variable frequency saturation transfer (VFST) method. This method is based on selective irradiation of numerous points in the spectrum and observation of changes in the intensity of visible line(s) which occur due to chemical exchange between it and lines which are not visible in the routine spectrum. Also, dissociation rate constants of MgADP-containing complexes were determined. Magnetization exchange rates, P-creatine ▪[γ-P]MgATP and [β-P]MgADP ▪[β-P]MgATP, were compared with radioisotope exchange rates, [γ- 32P-MgATP ▪P-creatine and [ 3H]MgADP ▪MgATP at different [ P-creatine] [ creatine] ratios and at different temperatures. All these exchange rates were close to each other at 30–37°C and [ PCr] [ Cr] ratios lower than 2. It is concluded that phosphoryl group transfer is the rate-determining step of the overall creatine kinase reaction under these conditions. However, at lower temperatures (below 25°C) or at high [ PCr] [ Cr] ratios ([ADP] < 20 μM) the rate-determining step seems to be shifted toward dissociation of nucleotide substrates from enzyme-substrate complexes, since exchange rates became significantly different. This approach is useful for analysis of mechanism of enzymatic reactions and also can be applied to non-enzymatic reactions and evaluation of small rapidly exchangeable metabolite pools.

High resolution magic angle spinning NMR studies of31P and11B in fast ion conducting AgI-Ag2O-P2O5 and AgI-Ag2O-B2O3 glasses

Silver iodide-based fast ion conducting glasses containing silver phosphate and silver borate have been studied. An attempt is made to identify the interaction between anions by studying the chemical shifts of31P and11B atoms in high resolution (HR) magic angle spinning (MAS) NMR spectra. Variation in the chemical shifts of31P or11B has been observed which is attributed to the change in the partial charge on the31P or11B. This is indicative of the change in the electronegativity of the anion matrix as a whole. This in turn is interpreted as due to significant interaction among anions. The significance of such interaction to the concept of structural unpinning of silver ions in fast ion conducting glasses is discussed.

ChemInform Abstract: APPLICATIONS OF VANADIUM‐51 AND PHOSPHORUS‐31 NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY TO THE STUDY OF ISO‐ AND HETERO‐POLYVANADATES

Vanadium-51 n.m.r. spectra of a number of iso- and hetero-polyvanadate anions are reported. Spectra of solutions containing [V10O28]6–(pH 6.5–3.5) are consistent with the known solid-state structure of this anion. The [VO2]+ cation in aqueous solution almost certainly has an octahedral cis-dioxo-structure as its n.m.r. linewidth is comparable with those for the cis compounds [VO2(04C2)2]3– and [VO2(edta)]3–(edta = ethylenediaminetetra-acetate), which are broader than those for pseudo-tetrahedral [VCl2O2]– and [VF2O2]–. Chemical shifts of pseudo-octahedral vanadium atoms in [VxW6–xO19]n–. [PVxW12–xO40]n–. [PMo12–xVxO40]n–, and [VVxW12–xO40]n– anions range from 506 to 545 p.p.m. (VCl3O reference) and linewidthsfrom 60 to 200 Hz (2.6–9 p.p.m.). Multiple lines in the specta of the 1 : 12 (Keggin) heteropolyanions confirm the existence of geometrical isomers distinguished by the relative positions of two or more vanadium atoms in the polyanion structure. Phosphorus-31 n.m.r. spectra confirm that most if not all of the possible isomers of this type areformed. The chemical shifts of 31P in [PMo12040]3– and [PW12040]3– are ca. 11 and 21 p.p.m. upfield from the unprotonated [PO4]3– ion (–6 with respect to 85% H,PO,). Introduction of V atoms in the heteropoly structures causes a progressive decrease in the chemical shift, enabling mixtures of such Keggin anions to be analyzed by n.m.r. A parallel variation in 51V chemical shift is found for [VO4]3–(536) and the tetrahedral vanadium in [VV3W9040]6–(553) and [VV2W10O40]5–(556 p.p.m.).

Applications of vanadium-51 and phosphorus-31 nuclear magnetic resonance spectroscopy to the study of iso- and hetero-polyvanadates

Vanadium-51 n.m.r. spectra of a number of iso- and hetero-polyvanadate anions are reported. Spectra of solutions containing [V10O28]6–(pH 6.5–3.5) are consistent with the known solid-state structure of this anion. The [VO2]+ cation in aqueous solution almost certainly has an octahedral cis-dioxo-structure as its n.m.r. linewidth is comparable with those for the cis compounds [VO2(04C2)2]3– and [VO2(edta)]3–(edta = ethylenediaminetetra-acetate), which are broader than those for pseudo-tetrahedral [VCl2O2]– and [VF2O2]–. Chemical shifts of pseudo-octahedral vanadium atoms in [VxW6–xO19]n–. [PVxW12–xO40]n–. [PMo12–xVxO40]n–, and [VVxW12–xO40]n– anions range from 506 to 545 p.p.m. (VCl3O reference) and linewidthsfrom 60 to 200 Hz (2.6–9 p.p.m.). Multiple lines in the specta of the 1 : 12 (Keggin) heteropolyanions confirm the existence of geometrical isomers distinguished by the relative positions of two or more vanadium atoms in the polyanion structure. Phosphorus-31 n.m.r. spectra confirm that most if not all of the possible isomers of this type areformed. The chemical shifts of 31P in [PMo12040]3– and [PW12040]3– are ca. 11 and 21 p.p.m. upfield from the unprotonated [PO4]3– ion (–6 with respect to 85% H,PO,). Introduction of V atoms in the heteropoly structures causes a progressive decrease in the chemical shift, enabling mixtures of such Keggin anions to be analyzed by n.m.r. A parallel variation in 51V chemical shift is found for [VO4]3–(536) and the tetrahedral vanadium in [VV3W9040]6–(553) and [VV2W10O40]5–(556 p.p.m.).

PMR spectra and steucture of esters of phosphonic acid

1. The PMR spectra of a number of esters of phosphonic acids RP(O)(OEt)2 where R represents alkyl or substituted alkyl, were studied. 2. The influence of the substituents on the chemical shift of the proton of the PCH fragment and the conditions of its correlation with the induction constants of the substituents, as well as with the chemical shift of31P of this fragment, was considered. 3. The spin-spin interaction constants2JHP and1JCP in the PMR and NMR-13C spectra of phosphonates show a correlated variation.

Associations intermoléculaires de composés du type (ou S)

The frequency shift between pure liquid and dilute solution in carbon tetrachloride has been measured for the PH valency vibration of forty compounds of general formula ▪ or ▪. It is supported that PH proton is able to form weak hydrogen bonds. The basicity of oxygen atom in PO has been estimated through determination of the 1 to 1 complex with phenol in dilute solution. There is a rough correlation between basicity and the electronegativities of X and Y. The results are compared with magnetic resonance chemical shift of 31P.