Rationalization of solid-state NMR multi-pulse decoupling strategies : coupling of spin I = ½ and half-integer quadrupolar nuclei

This work benefited from a grant from Agence Nationale de la Recherche (ANR MOSAIC 13-BS08-0018-01).In this paper we undertake a study of the decoupling efficiency of the Multiple-Pulse (MP) scheme, and a rationalization of its parameterization and of the choice of instrumental set up. This decoupling scheme is known to remove the broadening of spin-1/2 spectra I, produced by the heteronuclear scalar interaction with a half-integer quadrupolar nucleus S, without reintroducing heteronuclear dipolar interaction. The resulting resolution enhancement depends on the set-up of the length of the series of pulses and delays of the MP, and some intrinsic material and instrumental parameters. Firstly through a numerical approach, this study investigates the influence of the main intrinsic material parameters (heteronuclear dipolar and J coupling, quadrupolar interaction, spin nature) and instrumental parameters (spinning rate, pulse field strength) on efficiency and resolution enhancement of the scalar decoupling scheme. A guideline is then proposed to obtain quickly and easily the best resolution enhancement via the rationalization of the instrumental and parameter set up. It is then illustrated and tested through experimental data, probing the efficiency of MP-decoupling set up using this guideline. Various spin systems were tested (31P-51V in VOPO4, 31P-93Nb in NbOPO4, 119Sn-17O in Y2Sn2O7), combined with simulations results.PostprintPostprintPeer reviewe

95Mo nuclear magnetic resonance parameters of molybdenum hexacarbonyl from density functional theory: appraisal of computational and geometrical parameters.

International audienceSolid-state (95)Mo nuclear magnetic resonance (NMR) properties of molybdenum hexacarbonyl have been computed using density functional theory (DFT) based methods. Both quadrupolar coupling and chemical shift parameters were evaluated and compared with parameters of high precision determined using single-crystal (95)Mo NMR experiments. Within a molecular approach, the effects of major computational parameters, i.e. basis set, exchange-correlation functional, treatment of relativity, have been evaluated. Except for the isotropic parameter of both chemical shift and chemical shielding, computed NMR parameters are more sensitive to geometrical variations than computational details. Relativistic effects do not play a crucial part in the calculations of such parameters for the 4d transition metal, in particular isotropic chemical shift. Periodic DFT calculations were tackled to measure the influence of neighbouring molecules on the crystal structure. These effects have to be taken into account to compute accurate solid-state (95)Mo NMR parameters even for such an inorganic molecular compound

Synthesis and characterization of composite Hg-polyaniline powder material

International audienceA simple synthesis method is proposed to obtain a composite powder material constituted by polyaniline powder containing mercury droplets closely linked into PANI matrix. 199Hg solid state NMR spectroscopy indicates that incorporated mercury is in a metallic form and proves a redox reaction between polyaniline (leucoemeraldine form) and an aqueous solution of Hg(I). This composite powder material has been studied by voltammetry with a cavity microelectrode (CME). This electrode appears suitable for characterizing such a material. CME containing Hg-polyaniline (Hg-PANI) powder has been used as an electrochemical microsensor for lead trace analysis by anodic stripping voltammetry of water without electrolyte addition

Caractérisation structural multiéchelle de catalyseurs industriels de type vanadophosphate

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1H NMR Investigations of Activated Carbon Loaded with Volatile Organic Compounds: Quantification, Mechanisms, and Diffusivity Determination

International audienceThree volatile organic compounds (VOCs), benzene, cyclohexane, and dichloromethane, were adsorbed onto activated carbon fiber cloth. (1)H (magic-angle spinning (MAS) and pulsed field gradient (PFG)) NMR techniques were carried out, and the signals were analyzed in terms of peak surface areas and shifts. These techniques were shown to be very useful for determining (i) the intrinsic quantification of adsorbed molecules (VOCs and/or water) in the porosity of the materials (the adsorption capacities ranged from 0.2 to 4 mol·kg(-1)); (ii) the mechanisms of interactions between adsorbed organic molecules and the carbon walls (illustrations of positions of the molecule inside the pore volume are proposed; the proton-wall distance was less than 0.15 nm); and (iii) the diffusivities (surface diffusion coefficients (DS) were estimated at ≈4.10(-12) m(2)·s(-1) for cyclohexane, ≈1.10(-11) m(2)·s(-1) for benzene, and ≈4.10(-11) m(2)·s(-1) for dichloromethane)

Chemical Characterization and Botanical Origin of French Ambers

International audienceThe molecular composition of 10 Cretaceous andone Eocene ambers from France was analyzed by infraredspectroscopy, solid-state 13C nuclear magnetic resonance spectroscopy,and thermochemolysis gas chromatography−massspectrometry. The terpenoids identified in the samples wereused as biomarkers for the botanical origin of the resins. TheCretaceous samples, comprising the so-called Alpine, Anjou,Charentese, Provence, Pyrenean, and Vendean ambers, rangedfrom the Albian−Cenomanian transition to the early Santonian(100 to 85 Ma) and correspond to class Ib resins typical ofconifers. The extinct conifer family Cheirolepidiaceae wasproposed as the plant source of Pyrenean and brown Charenteseambers. Araucariaceae or Cheirolepidiaceae were the plant sourcesof the Cenomanian Alpine, Anjou, and yellow Charentese ambers.The Santonian ambers of Provence and Vendée were found to derive from the Cupressaceae. The Eocene Oise amber (ca. 53Ma) is a class Ic resin typical of angiosperms and was produced by a Fabaceae. The evolution of resin sources from the earlyCretaceous to the Eocene periods is discussed. Finally, a possible fingerprint hitherto unveiled is proposed for cheirolepidiaceousresins, defined by the simultaneous presence of phenolic diterpenoids, labdanoic acids, callitrisate structures, and their respectivederivatives

Utilisation de la RMN du solide paramagnétique pour déterminer le tenseur de susceptibilité magnétique local

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Utilization of solid-state NMR to determine the local magnetic susceptibility

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Combining in situ XRPD and solid state NMR to study ω-VOPO4 among industrial vanadium phosphate catalysts

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31P and 51V NMR studies of VOPO4 catalysts: vanadium decoupling, CSA amplification and NMR parameter calculations

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