1D 31P Research Articles

Spectroscopic, biochemical and computational studies of bioactive DNA minor groove binders targeting 5′-WGWWCW-3′ motif

Spectroscopic, biochemical, and computational modelling studies have been used to assess the binding capability of a set of minor groove binding (MGB) ligands against the self-complementary DNA sequences 5′-d(CGCACTAGTGCG)-3′ and 5′-d(CGCAGTACTGCG)-3′. The ligands were carefully designed to target the DNA response element, 5′-WGWWCW-3′, the binding site for several nuclear receptors. Basic 1D 1H NMR spectra of the DNA samples prepared with three MGB ligands show subtle variations suggestive of how each ligand associates with the double helical structure of both DNA sequences. The variations among the investigated ligands were reflected in the line shape and intensity of 1D 1H and 31P-{1H} NMR spectra. Rapid visual inspection of these 1D NMR spectra proves to be beneficial in providing valuable insights on MGB binding molecules. The NMR results were consistent with the findings from both UV DNA denaturation and molecular modelling studies. Both the NMR spectroscopic and computational analyses indicate that the investigated ligands bind to the minor grooves as antiparallel side-by-side dimers in a head-to-tail fashion. Moreover, comparisons with results from biochemical studies offered valuable insights into the mechanism of action, and antitumor activity of MGBs in relation to their structures, essential pre-requisites for future optimization of MGBs as therapeutic agents.

Small molecules dominate organic phosphorus in NaOH-EDTA extracts of soils as determined by 31P NMR

Understanding the composition of organic phosphorus (P) in soils is relevant to various disciplines, from agricultural sciences to ecology. Despite past efforts, the precise nature of soil organic P remains an enigma, especially that of the orthophosphate monoesters, which dominate 31P NMR spectra of NaOH-EDTA extracts of soils worldwide. The monoester region often exhibits an unidentified, broad background believed to represent high molecular weight (MW) P. We investigated this monoester background using 1D 31P NMR and 2D 1H31P NMR, as well as 31P transverse relaxation (T2) measurements to calculate its intrinsic linewidth and relate it to MW. Analyzing seven soils from different ecosystems, we observed linewidths of 0.5 to 3 Hz for resolved monoester signals and the background, indicating that it consists of many, possibly >100, sharp signals associated with small (<1.5 kDa) organic P molecules. This result was further supported by 2D 1H31P NMR spectra revealing signals not resolved in the 1D spectra. Our findings align with 31P NMR studies detecting background signals in soil-free samples and modern evidence that alkali-soluble soil organic matter consists of self-assemblies of small organic compounds mimicking large molecules.

Labile Metabolite Profiling in Human Blood Using Phosphorus NMR Spectroscopy.

Phosphorus metabolites occupy a unique place in cellular function as critical intermediates and products of cellular metabolism. Human blood is the most widely used biospecimen in the clinic and in the metabolomics field, and hence an ability to profile phosphorus metabolites in blood, quantitatively, would benefit a wide variety of investigations of cellular functions in health and diseases. Mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy are the two premier analytical platforms used in the metabolomics field. However, detection and quantitation of phosphorus metabolites by MS can be challenging due to their lability, high polarity, structural isomerism, and interaction with chromatographic columns. The conventionally used 1H NMR, on the other hand, suffers from poor resolution of these compounds. As a remedy, 31P NMR promises an important alternative to both MS and 1H NMR. However, numerous challenges including the instability of phosphorus metabolites, their chemical shift sensitivity to solvent composition, pH, salt, and temperature, and the lack of identified metabolites have so far restricted the scope of 31P NMR. In the current study, we describe a method to analyze nearly 25 phosphorus metabolites in blood using a simple one-dimensional (1D) NMR spectrum. Establishment of the identity of unknown metabolites involved a combination of (a) comprehensively analyzing an array of 1D and two-dimensional (2D) 1H/31P homonuclear and heteronuclear NMR spectra of blood; (b) mapping the central carbon metabolic pathway; (c) developing and using 1H and 31P spectral and chemical shift databases; and finally (d) confirming the putative metabolite peaks with spiking using authentic compounds. The resulting simple 1D 31P NMR-based method offers an ability to visualize and quantify the levels of intermediates and products of multiple metabolic pathways, including central carbon metabolism, in one step. Overall, the findings represent a new dimension for blood metabolite analysis and are anticipated to greatly impact the blood metabolomics field.

A thermosensitive gel matrix for bioreactor-assisted in-cell NMR of nucleic acids and proteins

Introducing the flow through the bioreactor has revolutionized in-cell NMR spectroscopy by prolonging the measurement time available to acquire spectral information about biomacromolecules in metabolically active cells. Bioreactor technology relies on immobilizer matrices, which secure cells in the active volume of the NMR coil and enable uniform perfusion of the growth medium, supplying fresh nutrients to the cells while removing toxic byproducts of their metabolism. The main drawbacks of commonly used matrices include the inability to recover intact cells post-measurement for additional analyses and/or requirements for specific operating temperatures. Here, we report on the development and characterization of a set of thermosensitive and nontoxic triblock copolymers based on poly(D,L-lactide)-b-poly(ethylene glycol)-b-poly(D,L-lactide) (PLA-PEG-PLA). Here, we show for the first time that these copolymers are suitable as immobilizer matrices for the acquisition of in-cell NMR spectra of nucleic acids and proteins over a commonly used sample temperature range of 15–40 °C and, importantly, allow recovery of cells after completion of in-cell NMR spectra acquisition. We compared the performances of currently used matrices in terms of cell viability (dye exclusion assays), cellular metabolism (1D 31P NMR), and quality of in-cell NMR spectra of two model biomacromolecules (hybrid double-stranded/i-motif DNA and ubiquitin). Our results demonstrate the suitability and advantages of PLA-PEG-PLA copolymers for application in bioreactor-assisted in-cell NMR.

Identification of phosphorus sites in amorphous LiPON thin film by observing internuclear proximities

Amorphous lithium phosphorus oxynitrides (LiPON), prepared by reactive magnetron sputtering, have become the electrolytes of choice for all-solid-state thin film microbatteries since its discovery in early 1990s. Nevertheless, there is still a lack of understanding of their atomic-level structure and its influence on ionic conductivity. Solid-state NMR spectroscopy represents a promising technique to determine the atomic-level structure of LiPON glasses but is challenging owing to its low sensitivity in the case of thin film materials. Recently, 31P solid-state NMR spectra of LiPON thin films were acquired under magic-angle spinning (MAS) conditions and assigned with the help of density functional theory (DFT) calculations of NMR parameters. However, the identification of the different P local environments in these materials is still a challenge owing to their amorphous structure and the lack of resolution of the 31P MAS NMR spectra. We show herein how the NMR observation of internuclear proximities helps to establish the nature of P sites in LiPON thin films. The 31P-14N proximities are probed by a transfer of population in double resonance (TRAPDOR) experiment, whereas 31P-31P proximities are observed using one-dimensional (1D) 31P double-quantum (DQ)-filtered and two-dimensional (2D) 31P homonuclear correlation spectra as well as dipolar dephasing experiments using DQ-DRENAR (DQ-based dipolar-recoupling effects nuclear alignment reduction) technique. The obtained NMR data further support the recently proposed assignment of 31P NMR signals of LiPON thin films. With the help of this assignment, the simulation of the quantitative 1D 31P NMR spectrum indicates that PO43- orthophosphate anions prevail in LiPON thin films and N atoms are mainly incorporated in [O3PNPO3]5− dimeric anions. PO3N4− isolated tetrahedra and [O3POPO3]4− anions are also present but in smaller amounts.

Contrasting Trivalent Lanthanide and Actinide Complexation by Polyoxometalates via Solution-State NMR.

Deciphering the solution chemistry and speciation of actinides is inherently difficult due to radioactivity, rarity, and cost constraints, especially for transplutonium elements. In this context, the development of new chelating platforms for actinides and associated spectroscopic techniques is particularly important. In this study, we investigate a relatively overlooked class of chelators for actinide binding, namely, polyoxometalates (POMs). We provide the first NMR measurements on americium-POM and curium-POM complexes, using one-dimensional (1D) 31P NMR, variable-temperature NMR, and spin-lattice relaxation time (T1) experiments. The proposed POM-NMR approach allows for the study of trivalent f-elements even when only microgram amounts are available and in phosphate-containing solutions where f-elements are typically insoluble. The solution-state speciation of trivalent americium, curium, plus multiple lanthanide ions (La3+, Nd3+, Sm3+, Eu3+, Yb3+, and Lu3+), in the presence of the model POM ligand PW11O397- was elucidated and revealed the concurrent formation of two stable complexes, [MIII(PW11O39)(H2O)x]4- and [MIII(PW11O39)2]11-. Interconversion reaction constants, reaction enthalpies, and reaction entropies were derived from the NMR data. The NMR results also provide experimental evidence of the weakly paramagnetic nature of the Am3+ and Cm3+ ions in solution. Furthermore, the study reveals a previously unnoticed periodicity break along the f-element series with the reversal of T1 relaxation times of the 1:1 and 1:2 complexes and the preferential formation of the long T1 species for the early lanthanides versus the short T1 species for the late lanthanides, americium, and curium. Given the broad variety of POM ligands that exist, with many of them containing NMR-active nuclei, the combined POM-NMR approach reported here opens a new avenue to investigate difficult-to-study elements such as heavy actinides and other radionuclides.

Unravelling the Reactivity of Framework Lewis Acid Sites towards Methanol Activation on H‐ZSM‐5 Zeolite with Solid‐State NMR Spectroscopy

AbstractUnderstanding the acid sites on zeolites is vital for the establishment of catalyst structure–activity relationship and exploration of their potential applications in heterogeneous catalysis. Here, we report the identification of active framework Lewis acid sites on ZSM‐5 zeolites. The structures of framework‐associated tri‐coordinated Al that is bonding with hydroxyl groups are determined by using one‐ dimensional (1D) 31P and two‐dimensional (2D) 31P‐{27Al} NMR spectroscopy of trimethylphosphine oxide probe molecule. 2D 13C‐{27Al} NMR correlation experiments allow the observation of favorable formation of methoxy species on the framework‐associated Al Lewis acid sites in methanol reaction at low temperature, which is corroborated by density functional theory calculations. These methoxy species contribute to the further conversion of methanol to hydrocarbons as active C1 species. The results provide new insights into the Lewis acidity of zeolites.

Naphthalen-2-yl 1-(benzamido(diethoxyphosphoryl)methyl)-1H-1,2,3-triazole-4-carboxylate

We have previously published new biheterocyclic phospohonic α-amino esters of the 1,2,3-triazole-benzimidazole and 1,2,3-triazole-carbazole type. The aim of the present paper was to describe a new phosponic aminoester bearing a triazole ring substituted in position 5 by an ester group. Thus, according to the same catalytic process used previously, the compound naphthalen-2-yl 1-(benzamido(diethoxyphosphoryl)methyl)-1H-1,2,3-triazole-4-carboxylate was synthesized with an excellent yield and high regioselectivity via the copper (I)-catalyzed alkyne–azide cycloaddition reaction (CuAAC), using diethyl (α-azido(benzamido)methyl)phosphonate (1) as a dipole and 2- naphthyl propiolate as a dipolarophile (2). The structure of the new compound was fully characterized by 1D (31P, 1H-, 13C-) and 2D (1H-1H and 1H-, 13C-) NMR spectroscopy, IR, and HRMS.

NMR Investigation of Transport in Polybenzimidazole/Polyphosphoric Acid Membranes Prepared Via Novel Synthesis Route

Previous work by the some of us has demonstrated enhanced electrochemical performance of polybenzimidazole (PBI) membranes with high phosphoric acid content prepared by the so-called PPA process.1 Methods of PBI synthesis that involve casting from an organic solvent cannot incorporate the more rigid PBIs characteristic of the PPA process due to their limited solubility. Recently, a carefully controlled drying method has been discovered in which a gel PBI membrane, made in the PPA process, is transformed into a dense PBI film. This method provides a synthetic route to PBI films without the use of any organic solvents. The dense PBI films with repeat unit para-PBI (Fig.1), were originally developed for flow battery applications. However they also can be re-doped in phosphoric acid to be used as a membrane in high-temperature fuel cells.The re-doped PBI films have displayed unprecedented ionic conductivity at elevated temperatures, similar to the starting PBI gel membranes prepared by the PPA process1, while also exhibiting enhanced mechanical properties. Temperature-dependent conductivity data for two of these films are displayed below. Sample A is the dried, densified, and re-acidified version of sample B, with a much lower acid content, ~18 mol PA/PBI repeat unit compared to 30 mol PA/PBI RU, respectively, but exhibits comparable conductivity (Fig. 2). Thus, in high-temperature fuel cell operation the electrochemical performance is similar, but performance degradation due to mechanical creep is reduced, leading to greater durability of the Version A PBI.In attempting to understand the enhanced proton conductivity of the modified PBI membrane despite its lower acid content, we performed both 1H and 31P nuclear magnetic resonance (NMR) measurements. Proton self-diffusion coefficients for four membranes two (A,C) prepared by the modified process and two (B,D) by the original PPA process, were measured by pulsed gradient NMR and plotted in Fig. 3.The results show significantly enhanced proton diffusivity, both in magnitude and in lower activation energy for sample A, which is consistent with its high conductivity despite lower acid content compared to the original PPA-processed membranes (B, D). We have also performed solid state 1D 31P and 2D 31P{1H} HETCOR NMR measurements, which yield additional information on structural differences between the membranes and how these differences may affect transport properties. Multinuclear NMR Study of the Effect of Acid Concentration on Ion Transport in Phosphoric Acid Doped Polybenzimidazole Membranes, N. Suarez, N.K.A.C. Kodiweera, P. Stallworth, S.G. Greenbaun, S. Yu, and B. Benicewicz, Journal of Physical Chemistry B, 116, 12545-51(2012). Figure 1

Elucidating the Location of Cd2+ in Post-synthetically Treated InP Quantum Dots Using Dynamic Nuclear Polarization 31P and 113Cd Solid-State NMR Spectroscopy

Indium phosphide quantum dots (InP QD) are a promising alternative to traditional QD materials that contain toxic heavy elements such as lead and cadmium. However, InP QD obtained from colloidal synthesis are often plagued by poor photoluminescence quantum yields (PL-QYs). In order to improve the PL-QY of InP QD, a number of post-synthetic treatments have been devised. Recently, it has been shown that InP post-synthetically treated with Lewis acid metal divalent cations (M-InP) exhibit enhanced PL-QY; however, the molecular structure and mechanism behind the improved PL-QY are not fully understood. To determine the surface structure of M-InP QD, dynamic nuclear polarization surface-enhanced nuclear magnetic resonance spectroscopy (DNP SENS) experiments were employed on a series of InP magic size clusters treated with Cd ions, InP QD, cadmium phosphide (Cd₃P₂) QD, and Cd-treated InP QD (Cd–InP QD). With the use of DNP SENS, we were able to obtain the 1D ³¹P and ¹¹³Cd NMR spectra, ¹¹³Cd{³¹P} rotational-echo double-resonance (REDOR) NMR spectra, and ³¹P{¹¹³Cd} dipolar heteronuclear multiple quantum correlation (D-HMQC) sequence. Changes in the phosphide ³¹P chemical shifts after Cd treatment provide indirect evidence that some Cd alloys into the sub-surface regions of the particle. DNP-enhanced ¹¹³Cd solid-state NMR spectra suggest that most Cd ions are coordinated by oxygen atoms from either carboxylate ligands or surface phosphate groups. ¹¹³Cd{³¹P} REDOR and ³¹P{¹¹³Cd} D-HMQC experiments confirm that a subset of Cd ions are located on the surface of Cd–InP QD and coordinated with phosphate groups.

Revealing the Structures in Short- and Middle-Order of Lanthanum-Doped Al2O3–NaPO3 Glasses by Solid State NMR Spectroscopy

Glasses in the xLa2O3-yAl2O3-(100 – x – y)NaPO3 system were synthesized by a melt quenching method, where 0 ≤ x ≤ 7.5, y = 0 and x = 5, 5 ≤ y ≤ 15. The structures were characterized by advanced multinuclei solid-state nuclear magnetic resonance spectroscopy (SSNMR) and X-ray photoelectron spectroscopy (XPS). 31P MAS NMR spectroscopy indicates that the glass Q2 structure is depolymerized by La2O3 and Al2O3, forming multiple QxAln and QyLan phosphorus species, where n, x, and y represent the number of P–O–P, P–O–Al, and P–O–La bonds, respectively. The various phosphorus species were identified by the J-coupling effect based one and two-dimensional (1D and 2D) experiments such as 2D J-resolved, 1D refocused INADEQUATE and 1D 31P{27Al} J-coupling heteronuclear multiple quantum coherence (HMQC). La is used as a mimic to simulate the local structure of the luminescent rare earth ions. 139La wideband uniform rate smooth truncation quadrupolar Carr–Purcell–Meiboom–Gill (WURST-QCPMG) spectra show that the coordination number of La is dominantly nine, and some La atoms transfer to lower coordination with the addition of Al2O3. La, Al, and Na atoms exclusively bond to phosphorus tetrahedron PO4, which is evidenced by the 31P/23Na, 31P/27Al double resonance NMR, XPS, and the calculation of charge balance. However, the Al/P and La/P connection methods are much different based on the calculation of charge balance and bond number. Finally, comprehensive and novel local structure models are developed for these rare earth-doped aluminum phosphate glasses.

Advanced solid state 1D/2D NMR investigation of the B2O3-Zn(PO3)2 glasses

In order to understand how the B2O3 insertion alters the structure and properties of the widely used zinc metaphosphate glass composition, advanced 1D/2D solid state MAS-NMR techniques were applied in this contribution to B2O3-Zn(PO3)2 glasses. High field (18.8 T) 1D NMR experiments allowed for a detailed characterization of the borate local order but did not provide much information about the phosphate speciation. We show how a set of 2D correlation NMR techniques could be applied to obtain additional data. First, 11B 2D DQ-SQ NMR spectra were edited to monitor the formation of the borate network through [x]BO[x]B linkages. In a second time, 11B(31P) D-HMQC technique was applied to characterize the formation of [x]BOP bonds and to provide additional information used to decompose the 1D 31P MAS-NMR experiments. This first 1D/2D NMR analysis of the B2O3-Zn(PO3)2 line was finally used to construct a structural model which shed light upon the glass transition temperature non-linear evolution.

Phosphorus NMR and Its Application to Metabolomics.

Stable isotopes are routinely employed by NMR metabolomics to highlight specific metabolic processes and to monitor pathway flux. 13C-carbon and 15N-nitrogen labeled nutrients are convenient sources of isotope tracers and are commonly added as supplements to a variety of biological systems ranging from cell cultures to animal models. Unlike 13C and 15N, 31P-phosphorus is a naturally abundant and NMR active isotope that does not require an external supplemental source. To date, 31P NMR has seen limited usage in metabolomics because of a lack of reference spectra, difficulties in sample preparation, and an absence of two-dimensional (2D) NMR experiments, but 31P NMR has the potential of expanding the coverage of the metabolome by detecting phosphorus-containing metabolites. Phosphorylated metabolites regulate key cellular processes, serve as a surrogate for intracellular pH conditions, and provide a measure of a cell's metabolic energy and redox state, among other processes. Thus, incorporating 31P NMR into a metabolomics investigation will enable the detection of these key cellular processes. To facilitate the application of 31P NMR in metabolomics, we present a unified protocol that allows for the simultaneous and efficient detection of 1H-, 13C-, 15N-, and 31P-labeled metabolites. The protocol includes the application of a 2D 1H-31P HSQC-TOCSY experiment to detect 31P-labeled metabolites from heterogeneous biological mixtures, methods for sample preparation to detect 1H-, 13C-, 15N-, and 31P-labeled metabolites from a single NMR sample, and a data set of one-dimensional (1D) 31P NMR and 2D 1H-31P HSQC-TOCSY spectra of 38 common phosphorus-containing metabolites to assist in metabolite assignments.

Solid-State NMR, X-Ray Diffraction, and Theoretical Studies of Neutral Mononuclear Molecular Bis(triphenylphosphine)silver(I) Mono-Carboxylate and -Nitrate Systems

Neutral mononuclear molecular silver(i) carboxylate complexes of the form [(Ph3P)2Ag(O2XY)] with O2XY=O2CCH2Ph, O2CCHPh2, O2CC(CH3)3, O2CCH2C(CH3)3, and O2CCF3 (compounds 1–4 and 5β) have been investigated in the solid state using single-crystal X-ray structure determinations, 1D 31P CPMAS NMR and 2D 31P–31P CPCOSY NMR measurements, and ab initio computational modelling. The results show that these complexes contain P2AgO2 molecular cores with four-coordinate silver in which the carboxylate ligands are weakly bound to the silver atoms via the two oxygen atoms giving rise to unsymmetrical chelate units. Crystal structure determinations and solid-state NMR spectra have also been analysed for the mononuclear molecular silver(i) nitrate complex [(Ph3P)2Ag(O2NO)] (9α) and two polymorphs of its toluene monosolvate (11α, β). In 9α, the two PPh3 ligands are of the same chirality, whereas in 11α, β, they are opposed. The crystalline environments in the polymorphs have been explored by way of Hirshfeld surface analyses, after quantum-mechanical isolated-molecule calculations had shown that although the molecular energies of the experimental geometries of 9α, and 11α, β are significantly different from each other and from the energies of the optimized geometries, the latter, in contrast, do not differ significantly from each other despite the conformational isomerism. It has further been shown using 9α as an example that the energy dependence on variation of the P–Ag–P angle over a range of ~15° is only ~5 kJ mol−1. All this indicates that the forces arising from crystal packing result in significant perturbations in the experimental geometries, but do not alter the stereoisomerism caused by the donor atom array around the Ag atom. In the NMR study, a strong inverse correlation has been found between 1J(107/109Ag,31P) and the Ag–P bond length across all carboxylate and nitrate compounds.

Durable BaO–ZnO–P2O5 glass with small stress‐induced birefringence for lead‐free polarization light‐controlling devices

AbstractBarium zinc phosphate glasses formulated in the xBaO–(60 − x)ZnO–40P2O5 composition line are investigated for their optical, thermal, and chemical characteristics. These as well as small stress‐induced birefringence were found to be governed by the BaO/ZnO substitution. In addition to the characterization of the properties, the phosphate network was qualitatively and quantitatively described in terms of Q2 and Q1 ratios by 1D 31P magic angle spinning nuclear magnetic resonance spectroscopy experiments that also showed the presence of Q0 sites. It turns out that the small perturbations of their photoelastic, magnetic, and chemical characteristics made these glasses very good candidates for use in polarization‐controlling optical devices.

New Insights into the Interactions of a DNA Oligonucleotide with mPEGylated-PAMAM by Circular Dichroism and Solution NMR.

Dendrimers are well-defined, highly branched, synthetic three-dimensional molecules with a large number of reactive end groups. PAMAM dendrimers form stable complexes with DNA chemistries and constitute an important class of nonviral, cationic vectors in gene delivery. The aim of this study isto examine the interactions of a 12 bp DNA oligonucletide with PAMAM-G2 and mPEG- b-PAMAM-G3 having eight surface amine groups under physiological conditions, using constant DNA concentration but varying dendrimer concentration. 1D 31P NMR, 2D NOESY, and CD spectroscopic methods were employed to investigate the interactions between the dendrimer and the DNA. The CD experiments carried out with a constant DNA concentration of 25 μM and dendrimer concentrations from 0 to 100 μM indicated minimal change to the chirality of the DNA for both types of dendrimers. While the PAMAM-G2 dendrimer caused aggregation of the majority of the DNA, the 2D NMR data of the DNA with an mPEG- b-PAMAM-G3 dendrimer indicated general broadening of the 1D 31P peaks from the DNA phosphates, a small number of 1H chemical shift perturbations (CSPs), and reduction of specific 1H-1H NOE intensities. These data suggest there is minimal structural alteration of the DNA in the complex and indicate preferential binding of the dendrimer to the central AATT region of the DNA sequence. The results herein are the first such results demonstrating a soluble DNA complex with the mPEG- b-PAMAM-G3 dendrimer analyzed by multidimensional NMR.

Diffusion-Ordered Nuclear Magnetic Resonance Spectroscopy (DOSY-NMR): A Novel Tool for Identification of Phosphorus Compounds in Soil Extracts.

Liquid-state, one-dimension 31P nuclear magnetic resonance spectroscopy (NMR) has greatly advanced our understanding of the composition of organic phosphorus in the environment. However, the correct assignment of signals is complicated by overlapping and shifting signals in different types of soils. We applied therefore for the first time diffusion-ordered spectroscopy (DOSY) to soil extracts, allowing us to separate phosphorus components in the second domain based on their translational diffusion coefficients. After successful application to a mixture of 14 model compounds, diffusion rates correlated closely with the molecular weight of the individual compound in aqueous solution (R2 = 0.97). The method was then applied to NaOH/EDTA extracts of a grassland soil, of which paramagnetic contaminations were removed with sodium sulfide following high-velocity centrifugation (21 500g, 45 min) at 4 °C. Diffusion rates in soil extracts were again closely related to molecular weight (R2 = 0.98), varying from 163.9 to 923.8 Da. However, our DOSY application failed for a forest soil with low organic phosphorus content. Overall, DOSY did help to clearly identify specific NMR signals like myo- and scyllo-inositol hexakisphosphate. It thus provides a more confident signal assignment than 1D 31P NMR, although currently the ubiquitous use of this novel methodology is still limited to soils with high organic phosphorus content.

31P-Solid-State NMR Characterization and Catalytic Hydrogenation Tests of Novel heterogenized Iridium-Catalysts

The synthesis of novel robust and stable iridium-based immobilized catalysts on silica-polymer hybrid materials (Si-PB-Ir) is described. These catalysts are characterized by a combination of ¹D ³¹P CP-MAS and 2D ³¹P-¹H HETCOR and J-resolved multinuclear solid state NMR experiments. Different binding situations such as singly and multiply coordinated phosphines are identified. Density functional theory (DFT) calculations are performed to corroborate the interpretation of the experimental NMR data, in order to propose a structural model of the heterogenized catalysts. Finally, the catalytic activity of the Si-PB-Ir catalysts is investigated for the hydrogenation of styrene employing para-enriched hydrogen gas.

Non-homogeneous distribution of Al3+ in doped phosphate glasses revealed by 27Al/31P solid state NMR

Solid state NMR is applied in this contribution on the xAl2O3-(50-x/2)Na2O-(50-x/2)P2O5 composition line (with 0<x<5mol%) in order to investigate the distribution of Al3+ ions in Al2O3-doped sodium phosphate glasses. The structure was analysed by (i) 27Al 1D-, 3Q-, DQ- MAS-NMR analysis and (ii) 1D 31P, 27Al(31P) 2D D-HMQC MAS-NMR and 2D 31P R-INADEQUATE technique. The 27Al NMR results confirm the presence of six-coordinated aluminate as major aluminate species and indicate that Al3+ ions are fully dissociated in the glass network. The 31P NMR data show the simultaneous presence of five different phosphate units connected to 0, 1 but also 2 Al3+ ions and offer a new vision of the doping mechanism by highlighting a non-homogeneous distribution of Al3+ ions in the phosphate matrix. This study indicates that the glass networks contain Al3+-rich and -poor domains and present thus a significant structural disorder beyond the local order.

31P-Solid-State NMR Characterization and Catalytic Hydrogenation Tests of Novel heterogenized Iridium-Catalysts

Abstract The synthesis of novel robust and stable iridium-based immobilized catalysts on silica-polymer hybrid materials (Si-PB-Ir) is described. These catalysts are characterized by a combination of 1D 31P CP-MAS and 2D 31P-1H HETCOR and J-resolved multinuclear solid state NMR experiments. Different binding situations such as singly and multiply coordinated phosphines are identified. Density functional theory (DFT) calculations are performed to corroborate the interpretation of the experimental NMR data, in order to propose a structural model of the heterogenized catalysts. Finally, the catalytic activity of the Si-PB-Ir catalysts is investigated for the hydrogenation of styrene employing para-enriched hydrogen gas.