Oxidative Alkoxylation of Hypophosphite in Coordination Sphere of Iron(III)

The kinetics of oxidation of sodium hypophosphite with oxygen in Fe(III) alcoholic solutions is studied. At 50-90°C, hypophosphite was found to be oxidized to dialkyl phosphite (RO)₂HPO, di-, and trialkyl phosphates (RO)₂(OH)PO, (RO)₃PO. The redox potentiometry, IR, UV, EPR, Mössbauer, and ³¹P NMR spectroscopies, X-ray powder diffraction analysis, and gas-liquid chromatography were used to determine the key stages of the process: the Fe(III) reduction with hypophosphite with the formation of the phosphorus ethers and the reoxidation of Fe(II) with oxygen. The molar ratio of the products depends on the composition of the Fe(III) coordination sphere.     

Characterizing mixed phosphonic acid ligand capping on CdSe/ZnS quantum dots using ligand exchange and NMR spectroscopy

The ligand capping of phosphonic acid functionalized CdSe/ZnS core–shell quantum dots (QDs) was investigated with a combination of solution and solid‐state ³¹P nuclear magnetic resonance (NMR) spectroscopy. Two phosphonic acid ligands were used in the synthesis of the QDs, tetradecylphosphonic acid and ethylphosphonic acid. Both alkyl phosphonic acids showed broad liquid and solid‐state ³¹P NMR resonances for the bound ligands, indicative of heterogeneous binding to the QD surface. In order to quantify the two ligand populations on the surface, ligand exchange facilitated by phenylphosphonic acid resulted in the displacement of the ethylphosphonic acid and tetradecylphosphonic acid and allowed for quantification of the free ligands using ³¹P liquid‐state NMR. After washing away the free ligand, two broad resonances were observed in the liquids' ³¹P NMR corresponding to the alkyl and aromatic phosphonic acids. The washed samples were analyzed via solid‐state ³¹P NMR, which confirmed the ligand populations on the surface following the ligand exchange process. Copyright © 2015 John Wiley & Sons, Ltd.     

Simultaneous determination of phenolic compounds and triterpenic acids in oregano growing wild in Greece by 31P NMR spectroscopy

³¹P nuclear magnetic resonance (NMR) spectroscopy was used to detect and quantify simultaneously a large number of phenolic compounds and the two triterpenic acids, ursolic acid and oleanolic acid, extracted from two oregano species Origanum onites and Origanum vulgare ssp. Hirtum using two different organic solvents ethanol and ethyl acetate. This analytical method is based on the derivatization of the hydroxyl and carboxyl groups of these compounds with the phosphorous reagent 2‐chloro‐4,4,5,5‐tetramethyl‐1,3,2‐dioxa phospholane and the identification of the phosphitylated compounds on the basis of the ³¹P chemical shifts. Unambiguous assignment of the ³¹P NMR chemical shifts of the dihydroxy‐ and polyhydroxy‐phenols in oregano species as well as those of the triterpenic acids was achieved upon comparison with the chemical shifts of model compounds assigned by using two‐dimensional NMR techniques. Furthermore, the integration of the appropriate signals of the hydroxyl derivatives in the corresponding ³¹P NMR spectra and the use of the phosphitylated cyclohexanol as an internal standard allowed the quantification of these compounds. The validity of this technique for quantitative measurements was thoroughly examined. Copyright © 2012 John Wiley & Sons, Ltd.     

Further evidence of incorporation of chromium ions into the framework of silicoaluminophosphate molecular sieves

Three different molecular sieves were synthesised and characterized using³¹P and²⁷Al magic angle spinning nuclear magnetic resonance (³¹P and²⁷Al MAS NMR) spectroscopy and acidity measurement techniques. The synthesized solids were: a silicoaluminophosphate (SAPO-11) sample, a chromium-substituted silicoaluminophosphate (CrAPSO-11) sample and a chromium-supported SAPO-11 (Cr/SAPO-11) sample. Significant differences were observed between the CrAPSO-11 MAS NMR spectra and the spectra for the other two solids. The differences can be understood in terms of a different chemical environment for the Al(III) and P(V) ions in the molecular sieve framework, as a result of a different type of interaction, probably with substituted chromium ions in the framework. The acidity measurements were in agreement with the MAS NMR spectroscopy results, providing further evidence for the incorporation of chromium ions into the molecular sieve framework.     

人宫颈癌细胞(Hela)内的31P核磁共振研究

建立了无损伤性³¹P NMR研究细胞内物质的实验方法, 并对人宫颈癌细胞(Hela)的³¹P NMR谱中含磷小分子代谢物的谱峰进行了分析; 细胞内无机磷(Pi)的化学位移对pH非常敏感, 通过测定其化学位移可间接确定细胞内的pH, Hela细胞内Pi峰的化学位移为5.88±0.01 (n＝3), 计算得到细胞内 pH值为7.05±0.01; 通过测量Hela细胞的³¹P NMR谱中ATP的α磷和β磷及γ磷的化学位移差值, 得出Hela细胞内Mg^2＋与ATP结合的复合物MgATP和整个ATP量的比值, 计算得到Hela细胞内游离Mg^2＋浓度为(253.3±0.13) mmol/L (n＝3), 与其它分析方法相比, ³¹P NMR测定细胞内游离Mg^2＋浓度具有对细胞样品无损伤的优点.     

A new signal processing method to observe weak P and O NMR peaks

In NMR spectroscopy, situations may arise where sample concentrations are below the threshold for FT NMR detection, or sample lability constrains allowable acquisition times. In ³¹P NMR, for example, observation of ¹³C satellites may not be practical under given conditions. For ¹⁷O NMR, which is useful to characterize ¹⁷O-labeled phosphate derivatives, similar considerations may apply, and added factors are the cost of isotopically enriched samples and the requirement to obtain spectra at relatively high temperatures if narrow spectral peak line widths are desired. We report here application of a new signal processing method [S.D. Kunikeev, H.S. Taylor, J. Phys. Chem. A 108, 2004 743] to observation of weak ³¹P and ¹⁷O NMR peaks.     

Atropisomerism of diastereomer diribonucleoside phosphotriester

Linear diribonucleoside phosphotriester is an important intermediate for synthesizing biologically important compounds,such as cyclic bis（3’-5’） diguanylic acid（c-di-GMP） and its analogues. Atropisomerism of diastereomers generated by the chiral center of the P atom,which results in the doubling of signals in ³¹P NMR.The data of ³¹P NMR at different temperature are presented,and thereafter the reason is discussed.     

Synthesis of Ethylene‐bridged Heterocyclic Bidentate P(III)N‐Ligands — Oxidation and Complexation Studies

A series of phosphor(III)inanone ligands 4‐7 , linked by ethylene bridges between the nitrogen atoms of the heterocyclic rings, were synthesized by the reaction of the bis‐PCl derivative 3 with the appropriate trimethylsilylamines. The bis‐phosphor(V)inanone compounds 8‐11 were obtained by the oxidation of 4‐7 with hexafluoroacetone (HFA). Oxidation of 4 and 6 with tetrachloro‐orthobenzoquinone (TOB) gave the bis‐phosphor(V)inanones 12 and 13 . The reaction of 4‐6 with [Pt(COD)Cl₂] led to the platinum complexes 14‐16 . All the σ³‐phosphorinanone compounds 4‐7 and the σ⁵‐phosphorinanone compounds 8‐10 , 12 and 13 exist as a mixture of two conformers, as indicated by two signals in the ³¹P‐NMR spectra. However, compounds 9 and 11 exist as single conformers, both display only one sharp singlet in the ³¹P‐NMR spectra. The Pt‐complexes 15 and 16 contain two conformers; one conformer of 16 could be isolated by crystallization. X‐ray crystal structure determinations for compounds 8 , 14 and 16 were conducted, revealing inversion symmetry for 8 and cis arrangement for 14 and 16 .     

Quantitative Distinction between Noble Metals Located in Mesopores from Those on the External Surface

We compare three methods for quantitatively distinguishing the location of noble metal (NM) particles in mesopores from those found on the external support surface. MCM-41 and SBA-15 with NM located in mesopores or on the external surface were prepared and characterized by TEM. ³¹P MAS NMR spectroscopy was used to quantify arylphosphines in complexes with NM. Phosphine/NM ratios drop from 2.0 to 0.2 when increasing the probe diameter from 1.08 to 1.54 nm. The reaction between NM and triphenylphosphine (TPP) within 3.0 nm MCM-41 pores takes due to confinement effects multiple weeks. In contrast, external NM react with TPP instantly. A promising method is filling the pores by using the pore volume impregnation technique with tetraethylorthosilicate (TEOS). TPP loading revealed that 66 % of NMs are located on the external surface of MCM-41. The pore filling method can be used in association with any probe molecule, also for the quantification of acid sites.     

Gold(I) Complexation with Trialkyl/Triaryl Phosphine Selenide Ligands

Abstract

A number of phosphine selenide ligands and their gold(I) complexes of general formula R₃P?Se?Au?X (where X is Cl^?, Br^? and CN^? and R = phenyl, cyclohexyl and tolyl) were prepared. The complexes were characterized by elemental analysis, IR and ³¹P NMR spectroscopic methods. In the IR spectra of all complexes a decrease in frequency of P?Se bond upon coordination was observed, indicating a decrease in P?Se bond order. ³¹P NMR showed that the electronegativity of the substituents is the most important factor determining the ³¹P NMR chemical shift. It was observed that phosphorus resonance is more downfield in alkyl substituted phosphine selenides, as compared to the aryl substituted ones. Ligand disproportionation in the complex Cy₃P?SeAuCN in solution to form [Au(CN)₂]^? and [(Cy₃P?Se)₂Au]⁺ was investigated by ¹³C and ¹⁵N NMR spectroscopy.     

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.     

Phase diagram and phase structure of the sodium di-n-pentyl phosphate-water system.1H pulsed-gradient NMR self-diffusion,31P NMR and x-ray diffraction studies

Sodium di-n-pentylphos phate (DPP) has been synthesized, and the phase diagram of the DPP-water system consisting of five regions (I, II, III, IV, and V) has been determined. The phase structure has been investigated by¹H pulsed-gradient NMR self-diffusion,³¹P NMR and x-ray low angle diffraction methods. The results are summarized as follows. In region I, there exist two critical micelle concentrations (CMC), indicating that this region is in a monomer-micelle equilibrium and that variation in the aggregated state occurs at the second CMC. Region II is a two phase area in which regions I and IV coexist. In region III, hydrated crystals and an aqueous solution of DPP coexist. Region IV is a homogenous, transparent and fluid phase and the results of³¹P NMR spectra and x-ray diffraction patterns reveal the formation of a highly organized structure, similar to a lamellar-like structure. Region V is a homogenous, transparent and fluid phase and the self-diffusion coefficient value and³¹P NMR spectra show that its phase structure is very similar to that for the concentrated sample in region I.     

Synthesis and characterization of an iron(III) complex of glycine derivative of bis(phenol)amine ligand in relevance to catechol dioxygenase active site

A glycine derivative of bis(phenol)amine ligand (HL^Gly) was synthesized and characterized by ¹H NMR and IR spectroscopies. The iron(III) complex (L^GlyFe) of this ligand was synthesized and characterized by IR, UV-Vis, X-ray and magnetic susceptibility studies. X-ray analysis reveals that in L^GlyFe the iron(III) center has a distorted trigonal bipyramidal coordination sphere and is surrounded by an amine nitrogen, a carboxylate and two phenolate oxygen atoms. The mentioned carboxylate group acts as μ-bridging ligand for iron centers of neighbor complexes. The variable-temperature magnetic susceptibility indicates that L^GlyFe is the paramagnetic high spin iron(III) complex. It has been shown that electrochemical oxidation of this complex is ligand-centered due to the oxidation of phenolate to the phenoxyl radicals. The L^GlyFe complex also undergoes an electrochemical metal-centered reduction of ferric to ferrous ion. The oxygenation of 3,5-di-tert-butyl-catechol, with L^GlyFe in the presence of dioxygen was investigated.     

Multinuclear magnetic resonance study of some imidovanadium complexes

¹⁴N NMR studies were carried out for a series of mononuclear and dinuclear vanadium complexes with different types of nitrogen ligands (terminal and µ‐imido, amido, nitrido, amine). Some complexes containing ancillary phosphine moieties were also characterized by ³¹P NMR spectroscopy. The observed shieldings for terminal and bridging imido ligands are intermediate between those of nitrido and amido moieties, and the latter appear less shielded than coordinated tertiary amines. The ranges for individual ligand types are sufficiently resolved to allow the use of nitrogen chemical shifts as a structure assignment tool. The ¹⁴N NMR signals of terminal and bridging imido nitrogens displayed marked differences in their lineshapes which could be used as an additional criterion for signal assignment. Examination of substituent influences revealed the absence of a general parallelism between δ¹⁴N and δ⁵¹V, but gave evidence for parallel relationships between both quantities for complexes with formal 12VE and 16VE electron counts. Determination of ¹J(⁵¹V,¹⁴N) and ¹J(⁵¹V,³¹P) coupling constants in mononuclear complexes was feasible from simulation of ¹⁴N and ³¹P lineshapes and suggested that imido ligands exhibit generally greater couplings to vanadium than amido ligands. Analysis of the ³¹P {¹H,¹⁴N} NMR spectrum allowed us to determine ²J(⁵¹V,³¹P) for the vanadacycle cyclo(^tBuN—P?C(^tBu)—VCl₃—). It was shown that both couplings can be employed for the acquisition of two‐dimensional ³¹P,⁵¹V shift correlations. Copyright © 2001 John Wiley & Sons, Ltd.     

Phosphate additives determination in meat products by 31-phosphorus nuclear magnetic resonance using new internal reference standard: hexamethylphosphoroamide

New ³¹P NMR internal reference standard - hexamethylphosphoroamide (HMPA) was applied for determination of added polyphosphates and their ionic forms in raw pork meat and meat products. Phosphate species were determined after extraction with a boric acid buffer (pH = 9) and EDTA solution, using internal standard (HMPA) procedure. Hexamethylphosophoroamide was also used as the NMR reference standard. Linear correlations between phosphates and polyphosphate concentrations and ³¹P NMR signal areas were found in the range 81-5236 mg P/dm³, presenting 95-99% recovery and variation coefficient (CV) ≤ 5%. Studied HMPA procedure revealed shorter analysis time and the same recovery (>95%) and precision (CV = 1.3-2.7%) in comparison to MDPA method. Results of phosphate determination by both ³¹P NMR methods were tested against the molybdenumvanadate yellow spectrophotometric method (standard PN-ISO 13730, 1999) using standard reference material (certified phosphate solution).     

Solid-State Nuclear Magnetic Resonance Techniques for the Structural Characterization of Geminal Alane-Phosphane Frustrated Lewis Pairs and Secondary Adducts

The first comprehensive solid-state nuclear magnetic resonance (NMR) characterization of geminal alane-phosphane frustrated Lewis pairs (Al/P FLPs) is reported. Their relevant NMR parameters (isotropic chemical shifts, direct and indirect ²⁷Al-³¹P spin-spin coupling constants, and ²⁷Al nuclear electric quadrupole coupling tensor components) have been determined by numerical analysis of the experimental NMR line shapes and compared with values computed from the known crystal structures by using density functional theory (DFT) methods. Our work demonstrates that the ³¹P NMR chemical shifts for the studied Al/P FLPs are very sensitive to slight structural inequivalences. The ²⁷Al NMR central transition signals are spread out over a broad frequency range (>200 kHz), owing to the presence of strong nuclear electric quadrupolar interactions that can be well-reproduced by the static ²⁷Al wideband uniform rate smooth truncation (WURST) Carr-Purcell-Meiboom-Gill (WCPMG) NMR experiment. ²⁷Al chemical shifts and quadrupole tensor components offer a facile and clear distinction between three- and four-coordinate aluminum environments. For measuring internuclear Al⋅⋅⋅P distances a new resonance-echo saturation-pulse double-resonance (RESPDOR) experiment was developed by using efficient saturation via frequency-swept WURST pulses. The successful implementation of this widely applicable technique indicates that internuclear Al⋅⋅⋅P distances in these compounds can be measured within a precision of ±0.1 Å.     

NOESY,HOESY, T1 and solid‐state NMR studies on [RuH(η6‐toluene)(Binap)](CF3SO3): a molecule with a strongly distorted piano‐stool structure

Detailed solution‐NMR studies on the distorted ruthenium hydride complex [RuH(η⁶‐toluene)(Binap)](CF₃SO₃) (2) are reported. NOE‐spectroscopy, together with low‐temperature ¹H and ³¹P NMR data, reveals restricted rotation around a P—C bond for a specific axial P—phenyl ring with the activation energy determined via simulation. From ¹⁹F, ¹H HOESY data, the approach of the triflate anion relative to the hydride ligand is established. Comparison of the quadrupole coupling constant C_QF from both solution‐ and solid‐state MAS‐NMR on the deuteride [RuD(η⁶‐benzene)(Binap)](CF₃SO₃) (1‐D) provide information on the nature of the Ru—H bond. Copyright © 2003 John Wiley & Sons, Ltd.     

Dihydrogen Splitting by Intramolecular Borane-Phosphane Frustrated Lewis Pairs: A Comprehensive Characterization Strategy Using Solid State NMR and DFT Calculations

Four hydrogenated intramolecular phosphane-borane frustrated Lewis pair (B/P FLP) compounds bearing unsaturated cyclic or aromatic carbon backbones have been synthesized and structurally characterized using ¹¹B, ³¹P, ¹H and ²H solid-state NMR spectroscopy. A comparison of the spectra with those of the corresponding free B/P FLPs shows that both ¹¹B isotropic chemical shifts as well as nuclear electric quadrupolar coupling constants decrease significantly upon FLP hydrogenation, revealing the breakage of the partial B−P bond present in the starting materials. Likewise, the ³¹P isotropic chemical shift, the chemical shift anisotropy, and the asymmetry parameter decrease significantly upon FLP hydrogenation, reflecting the formation of a more symmetric, C_3v-like local environment. ¹¹B{³¹P} rotational echo double resonance (REDOR) experiments can be used to measure the B−P internuclear distance (about 3.2 Å) of these compounds. Observation of the hydrogen atoms bound to the Lewis centers is best accomplished via ³¹P{¹H} and ¹¹B{¹H} cross-polarization-heteronuclear correlation experiments or by direct observation of the ²H MAS NMR signals on especially prepared FLP-D₂ adducts. For accurately measuring the phosphorus-deuterium distance via ³¹P{²H} rotational echo adiabatic passage double resonance (REAPDOR), it is essential to take the secondary dipolar coupling of ³¹P with the boron-bonded ²H nuclei explicitly into consideration, by simulating a ²H_P-³¹P-²H_B three-spin system based on structural input. All of the experimental NMR interaction parameters are found in excellent agreement with values calculated by DFT methods, using the geometries obtained either by energy optimization or from single-crystal structures.     

Towards the versatile DFT and MP2 computational schemes for 31P NMR chemical shifts taking into account relativistic corrections

The main factors affecting the accuracy and computational cost of the calculation of ³¹P NMR chemical shifts in the representative series of organophosphorous compounds are examined at the density functional theory (DFT) and second‐order Møller–Plesset perturbation theory (MP2) levels. At the DFT level, the best functionals for the calculation of ³¹P NMR chemical shifts are those of Keal and Tozer, KT2 and KT3. Both at the DFT and MP2 levels, the most reliable basis sets are those of Jensen, pcS‐2 or larger, and those of Pople, 6‐311G(d,p) or larger. The reliable basis sets of Dunning's family are those of at least penta‐zeta quality that precludes their practical consideration. An encouraging finding is that basically, the locally dense basis set approach resulting in a dramatic decrease in computational cost is justified in the calculation of ³¹P NMR chemical shifts within the 1–2‐ppm error. Relativistic corrections to ³¹P NMR absolute shielding constants are of major importance reaching about 20–30 ppm (ca 7%) improving (not worsening!) the agreement of calculation with experiment. Further better agreement with the experiment by 1–2 ppm can be obtained by taking into account solvent effects within the integral equation formalism polarizable continuum model solvation scheme. We recommend the GIAO‐DFT‐KT2/pcS‐3//pcS‐2 scheme with relativistic corrections and solvent effects taken into account as the most versatile computational scheme for the calculation of ³¹P NMR chemical shifts characterized by a mean absolute error of ca 9 ppm in the range of 550 ppm. Copyright © 2014 John Wiley & Sons, Ltd.