Layered metal(IV) phosphonate materials: Solid‐state 1H, 13C, 31P NMR spectra and NMR relaxation

Multinuclear solid‐state NMR and powder X‐ray diffraction data collected for phosphonate materials Zr(O₃PC₆H₄PO₃) · 3.6H₂O and Sn(O₃PC₆H₄PO₃)_0.85(O₃POH)_0.30 · 3.09H₂O have resulted in the layered structure, where the phosphonic acids cross‐link the layers. The main structural motif (the 111 connectivity in the PO₃ group) has been established by determination of chemical shift anisotropy parameters for phosphorus nuclei in the phosphonate groups. An analysis of the variable‐temperature ³¹P T₁ measurements and the shapes of the phosphorus resonances in the ³¹P static NMR spectra have resulted in the dipolar mechanism of the phosphorus spin‐lattice relaxation, where the rotating phenylene rings reorient dipolar vectors P^…H as a driving force of the relaxation process. It has been found that water protons do not affect the ³¹P T₁ times. The activation energy of the phenylene rotation in both compounds has been determined as low as 12.5 kJ/mol. The interpretation of the phosphorus relaxation data has been independently confirmed by the measurements of ¹H T₁ times for protons of the phenylene rings.     

Determination of 31P,31P coupling constants in cyclotriphosphazenes and their influence on 1H and 13C NMR spectra of phosphorus substituents

¹H and ¹³C NMR spectra of symmetrically substituted cyclotriphosphazenes exhibit second‐order effects. The influence of the ³¹P,³¹P coupling constants between ring phosphorus atoms on these effects was studied. Some values of this coupling constant between phosphorus bearing identical substituents were measured using ¹³C satellites of the ³¹P signals or by introduction of a chiral substituent on the third phosphorus atom. Copyright © 2003 John Wiley & Sons, Ltd.     

31P NMR Study on Some Phosphorus-Containing Compounds

In view of the facts that the phenomena of aggregation are inseparably related to life processes and that phosphorus-containing compounds are one of the essential building blocks of life, we have studied the aggregation behavior of some phosphonates and phosphinates1. The application of NMR to the problems in chemistry has become rather popular. In phosphorus-containing compounds, phosphorus is a central or backbone atom in molecular structures. 31P NMR is of importance and special value in …     

Complete 1H, 13C, 19F and 31P NMR data assignment of CWC‐related chemicals N,N‐dialkyl‐P‐alkyl phosphonamidic fluorides

The complete multinuclear ¹H, ¹³C, ³¹P and ¹⁹F NMR data of symmetrically substituted amines containing N,N‐dialkyl‐P‐alkyl phosphonamidic fluorides are presented. Assignment was achieved, using various one‐and two‐dimensional NMR experiments. Copyright © 2010 John Wiley & Sons, Ltd.     

31P NMR assessment of the phosvitin-iron complex in mayonnaise

Lipid oxidation is the main reason for the limited shelf life of mayonnaise. One of the main catalysts of this process is iron, which is introduced in its ferric (Fe(III)) form via phosvitin, an egg yolk phosphoprotein rich in phosphoserines. The binding of Fe(III) to phosvitin and its ability to establish a redox couple with Fe(II) is believed to determine the oxidation rate of unsaturated lipids. In this work, a ³¹P NMR based method was developed to quantify loading of phosvitin with Fe(III) and its reductive release. Both features could be quantified in model phosvitin solutions by exploiting the paramagnetic broadening of ³¹P NMR signal of phosphoserine residues by Fe(III). This method was then successfully applied to quantify the phosvitin-Fe(III) loading in mayonnaise water phase by liquid NMR, whereas ³¹P NMR MAS could only provide a qualitative measure. The ³¹P NMR method showed a direct relation between loading of the Fe(III)-phosvitin complex and lipid oxidation.     

31P Solid state NMR study of structure and chemical stability of dichlorotriphenylphosphorane

Solid state ³¹P NMR spectroscopy was used to examine, monitor and quantify the compound integrity of the chemical reagent dichlorotriphenylphosphorane. Comparison was also made with solution ³¹P NMR spectra which showed that this highly reactive species could be observed in dry benzene prior to conversion to the hydrolyzed product. This is the first reported solid state NMR study of the stability and reactivity of dichlorotriphenylphosphorane and the first account of its observation and comparison in the solution state. In the solid state, the ionic and covalent forms for dichlorotriphenylphosphorane were observed along with hydrolyzed products, however, the degree of hydrolysis was dependent upon the rotor packing conditions. Calculation of the relative percent composition of dichlorotriphenylphosphorane with hydrolyzed product was made for samples prepared in air versus under nitrogen atmosphere. This information was critical in adjusting the amount of reagent used in chemical development syntheses and scale up laboratories. All hydrolyzed products were identified, based upon chemical comparisons with spectra of pure materials. Copyright © 2009 John Wiley & Sons, Ltd.     

^31P NMR Studies on the Ligand Dissociation of Trinuclear Molybde-num Cluster Compounds

A series of carboxylate-substituted trinudear molybdenum dus-ter compounds formulated as Mo3S4(DTP)3(RCO2)(L), where RffiH, CH3, C2H5, CH2Cl, CCl3, R^1C6H4(R^1 is the group on the benzene ring of aromatic carboxylate ), L=pyridine,CH3CN, DMF, have been synthesized by the ligand substitu-tion reaction. The dissociation of the loosely-coordinated ligand L from the cluster core was studied by ^31p NMR. The dissocia-tion process of L is related to the solvent, temperature, and acidity of carboxylate groups, so as to affect the solution struc-ture and reactive properties of the duster. The long-distance in-teraction between ligands RCO2 and L is transported by Mo3S4 core.     

Application of <Superscript>31</Superscript>P NMR for added polyphosphate determination in pork meat

Application of ³¹P NMR for qualitative and quantitative determination of added phosphorus compounds in meat samples is described. Furthermore, usefulness of the proposed method for monitoring of poly- and pyrophosphates hydrolysis in meat is discussed. Calibration curves based on the ³¹P resonance line areas were elaborated for Na₃P₃O₉, Na₅P₃O₁₀, Na₂H₂P₂O₇, and K₄P₂O₇ resulting in linearity (R ² = 0.9976, 0.9953, 0.9974, and 0.9524, respectively), detection limits (DL from 0.0018 mol L⁻¹ for Na₃P₃O₉ to 0.0070 mol L⁻¹ for K₄P₂O₇), and quantification limits (QL from 0.0060 mol L⁻¹ for Na₃P₃O₉ to 0.0234 mol L⁻¹ for K₄P₂O₇). The developed procedure was applied for laboratory prepared meat samples and compared with the standard UV-VIS method. The minimal sample pretreatment, obtained within-day precision (CV ≤ 2.0 %) and accuracy (as recovery ≥ 95 %) suggest ³¹P NMR as an alternative method of phosphorus determination in food analysis.     

Solid‐state NMR study of dopant effects on the chemical properties of Mg‐, In‐, and Al‐doped SnP2O7

The effects of doped low‐valence cations on the properties of the SnP₂O₇ proton conductor at ambient temperature are investigated from changes in solid‐state NMR spectra and nuclear magnetic relaxation times. Although the T₁H values increased with decreasing acidity as a result of cation exchange, the ¹H chemical shifts moved to lower field in Al‐ and In‐doped materials compared with undoped ones. Furthermore, the shifts changed to higher field in Mg‐doped materials, suggesting the existence of different protonic species in those materials. The bulk phosphate chemical shifts in the ³¹P dipolar‐decoupling MAS NMR spectra were very similar, regardless of the nature and amount of the doping species. On the other hand, by ¹H/³¹P cross‐polarization MAS NMR, P₂O₇ signals interacting with an interstitial proton [Q¹(proton)] were observed in all the undoped and doped SnP₂O₇, while acidic P–OH‐type phosphate signals [Q¹(acid)] were additionally observed in the Mg‐doped conductor. The different affinity of the proton with the dopants and phosphates caused lower conductivity and larger activation energy in the Mg‐doped materials, compared with those in the In‐ and Al‐doped materials. Copyright © 2014 John Wiley & Sons, Ltd.     

Solid‐state NMR spectroscopy of Pb‐rich apatite

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. Copyright © 2009 John Wiley & Sons, Ltd.     

Quantitative 31P‐NMR spectroscopy for the determination of fosfomycin and impurity A in pharmaceutical products of fosfomycin sodium or calcium

A quantitative ³¹P‐NMR method for the determination of fosfomycin and impurity A in pharmaceutical products of fosfomycin sodium or calcium has been developed. In this method, coaxial inserts containing trimethyl phosphate are used as external standard. The method is convenient and robust, and gives both high accuracy and precision. It is shown that an accurate determination is possible using different probes and coaxial inserts. Copyright © 2015 John Wiley & Sons, Ltd.     

31P NMR spectroscopy in the quality control and authentication of extra-virgin olive oil: a review of recent progress

This review is a brief account on the application of a novel methodology to the quality control and authentication of extra-virgin olive oil. This methodology is based on the derivatization of the labile hydrogens of functional groups, such as hydroxyl and carboxyl groups, of olive oil constituents with the phosphorus reagent 2-chloro-4,4,5,5-tetramethyldioxaphospholane, and the use of the (31)P chemical shifts to identify the phosphitylated compounds. Various experimental aspects such as pertinent instrumentation, sample preparation, acquisition parameters and properties of the phosphorus reagent are reviewed. The strategy to assign the (31)P signals of the phosphitylated model compounds and olive oil constituents by employing 1D and 2D NMR experiments is presented. Finally, the capability of this technique to assess the quality and the genuineness of extra-virgin olive oil and to detect fraud is discussed.     

用31P NMR研究硫代磷酸酯水解反应历程

磷酸酯的水解反应是一类较为重要的反应,了解这类反应历程及机理对研究农药的毒性、环境保护、及指导农药的生产与合成具有十分重要的意义。~(31)PNMR灵敏度高,化学位移范围宽,偶合常数大.~(31)P NMR的化学位移对于分子中磷原子的价态、与磷原子直接相连的原子或基团的类型、数量、性质及构型的变化十分敏感.是研究有关含磷化合物结构问题的有效手段之一,因此本文采用~(31)P NMR方法研究了疏代磷酸酯的水解反应历程。本文所研究的化合物是一种新合成的含七元环的二硫代磷酸酯。其结构式如下:     

Phosphorylated amino acids: model compounds for solid-state 31P NMR spectroscopic studies of proteins

Solid-state 31P NMR spectroscopy was applied to measure the isotropic chemical shifts, chemical shift anisotropies and asymmetry parameters of three phosphorylated amino acids, O-phospho-L-serine, O-phospho-L-threonine and O-phospho-L-tyrosine. The cross-polarization buildup rates and longitudinal relaxation times of 31P and 1H were-determined and compared with the values measured for a triphosphate (GppCH2p) bound to a crystalline protein (Ras). It is shown that the phosphorylated amino acids are well-suited model compounds, e.g. for the optimization of experiments on crystalline proteins. Two-dimensional exchange experiments on O-phospho-L-tyrosine indicate the existence of an exchange between the two different conformations of the molecule.     

Investigation of Reaction Mechanism of Amino Acids and Phosphorus Trichloride by 31P NMR and ESI‐MS/MS

The reaction of amino acids and phosphorus trichloride in THF was studied by ³¹P NMR tracing and ESI‐MS/MS. A series of hydridophoranes and cyclic dipeptides were obtained. The reaction presented interesting diversity and the reaction mechanism was proposed. The mechanism suggests that phosphorus plays an important role in the synthesis of amino acid hydridophorane and cyclic dipeptides. The results also show that ³¹P NMR and ESI‐MS/MS are useful tools for the investigation of reaction mechanism.     

Solid‐state NMR characterization of tri‐ethyleneglycol grafted polyisocyanopeptides

In aqueous media, ethylene glycol substituted polyisocyanopeptides (PICPs) change their state (undergo a sol‐to‐gel transition) as a response to temperature. This makes them promising materials for various biomedical applications, for instance, for controlled drug release and non‐damaging wound dressing. To utilize PICP in biomedical applications, understanding of the origin of the gelation process is needed, but this is experimentally difficult because of the notoriously low gelator concentration in combination with the slow polymer dynamics in the sample. This paper describes a detailed characterization of the dried state of PICPs by solid‐state NMR measurements. Both the ¹³C and the ¹H NMR resonances were assigned using a combination of 1D cross‐polarization magic angle spinning, 2D ¹³C–¹H heteronuclear correlation spectra and ¹H–¹H single quantum–double quantum experiments. In addition, the chemical groups involved in dipolar interaction with each other were used to discuss the dynamics and spatial conformation of the polymer. In contrast to other PICP polymers, two resonances for the backbone carbon are observed, which are present in equal amounts. The possible origin of these resonances is discussed in the last section of this work. The data obtained during the current studies will be further used in elucidating mechanisms of the bundling and gelation. A comprehensive picture will make it possible to tailor polymer properties to meet specific needs in different applications. Copyright © 2015 John Wiley & Sons, Ltd.     

P NMR peak width in humate–phosphate complexes

The mobility of inorganic phosphate (P) attached to solid humic acid (HA) and fulvic acid (FA) via a metal “anchor” was investigated by ³¹P NMR spectroscopy. The peak width of the ³¹P resonance was monitored as an indicator of the degree of attachment of the element to the humic matrix. The concept was demonstrated by contrasting peak widths of thoroughly dry M–HA–P complexes with those that had been allowed to absorb different amounts of moisture. It was shown that the presence of moisture, which enhances the mobility of P, results in a significant reduction of chemical shift peak width. The work was extended to comparisons between dry systems with and without metal anchors; systems with anchors consisting of different metals; systems comprising different humates and fulvates; and systems with different size fractions of a humate. It was shown that both the type of humate/fulvate, and the metal anchor used lead to different degrees of mobility within the humic matrix. It was also found that the effect of metal addition on ³¹P peak width is greater with fulvates and smaller HA fractions than with the larger HA components.     

Recent advances in computational 31P NMR: Part 1. Chemical shifts

This is the first part of two closely related reviews dealing with the computation of phosphorus-31 nuclear magnetic resonance chemical shifts in a wide series of organophosphorus compounds including complexes, clusters, and bioorganic phosphorus compounds. In particular, the analysis of the accuracy factors, such as substitution effects, solvent effects, vibrational corrections, and relativistic effects, is presented. This review is dedicated to the Full Member of the Russian Academy of Sciences Professor Boris A. Trofimov in view of his invaluable contribution to the field of synthesis, nuclear magnetic resonance, and computation studies of organophosphorus compounds.     

31P NMR and HPLC Investigations of the Cyclophosphamide Metabolite,Phosphoramide Mustard

Abstract

Phosphoramide mustard (PM), a key active metabolite of the widely used anticancer drug cyclophosphamide (CP), can exist in several closely-related ionized, cyclized and substituted forms. We have developed a high pressure liquid chromatographic (HPLC) method for analysing serum concentrations of PM in order to relate these serum concentrations to toxicity and efficacy of treatment of CP. ³¹p NMR spectroscopy is used to verify the HPLC peak homology of the proposed PM peak.     

The bonding situation in 1,3,2‐diazaphospholene derivatives as studied by solid‐state NMR spectroscopy

The ³¹P chemical shift (CS) tensors of the 1,3,2‐diazaphospholenium cation 1 and the P‐chloro‐1,3,2‐diazaphospholenes 2 and 3 and the ³¹P and ¹⁹F CS tensors of the P‐fluoro‐1,3,2‐diazaphospholene 4 were characterized by solid‐state ³¹P and ¹⁹F NMR studies and quantum chemical model calculations. The computed orientation of the principal axes system of the ³¹P and ¹⁹F CS tensors in the P‐fluoro compound was found to be in good agreement with experimentally derived values obtained from evaluation of P–F dipolar interactions. A comparison of the trends in the chemical shifts of 1 – 4 with further available literature data confirms that the unique high shielding of δ₁₁ in the cation 1 can be related to the effective π‐conjugation in the five‐membered heterocycle, and that a further systematic decrease in δ₁₁ for the P‐halogen derivatives 2 – 4 is attributable to the increased perturbation of the π‐electron distribution by interaction with the halide donor. Copyright © 2002 John Wiley & Sons, Ltd.