Te NMR for structural investigations in phase change materials: Optimization of experimental conditions coupled to NMR shift prediction.

Phase Change Materials as those of the Ge-Sb-Te ternary system are of great interest for technological applications. Properties of these compounds are strongly related to presence of vacancies and structural investigations remain challenging. In this paper we evidence that Te NMR in natural abundance and using commercial systems at intermediate field (14.

Functionalised polyhedral oligomeric silsesquioxane with encapsulated fluoride - first observation of fluxional SiF interactions in POSS.

The synthesis of a styryl functionalised POSS incorporating an encapsulated fluoride ion within a (SiO) cage (T-F) is reported. It was characterised by single crystal XRD, MALDI-MS, FTIR, solution (Si, F, C, H) and solid state (Si, F) NMR. In the absence of H decoupling, the Si solution NMR spectrum exhibited a triplet of doublets.

Controlled grafting of dialkylphosphonate-based ionic liquids on γ-alumina: design of hybrid materials with high potential for CO separation applications.

In this work we provide a detailed study on grafting reactions of various dialkylphosphonate-based ILs. Special attention has been devoted to a comprehensive investigation on how the nature of the anion and the organic spacer composition (hydrophilic or hydrophobic groups) could impact the grafting densities and bonding modes of phosphonate-based ILs anchored to γ-alumina (γ-AlO) powders. For the first time, the bonding of phosphonate-based ILs with only surface hexacoordinated aluminum nuclei was established using both solid-state P-Al D-HMQC and P NMR experiments.

P-O-B(3) linkages in borophosphate glasses evidenced by high field (11)B/(31)P correlation NMR.

The long-standing debate about the presence of P-O-B(3) linkages in glasses has been solved by high-field scalar correlation NMR. Previously suggested by dipolar NMR methods, the presence of such species has been definitively demonstrated by (11)B((31)P) J-HMQC NMR techniques. The results indicate that borophosphate networks contain P-O-B(3) bonds and thus present a higher degree of atomic homogeneity than previously thought.

Advances in structural analysis of fluoroaluminates using DFT calculations of 27Al electric field gradients.

Based on the analysis of 23 aluminum sites from 16 fluoroaluminates, the present work demonstrates the strong potential of combining accurate NMR quadrupolar parameter measurements, density functional theory (DFT)-based calculations of electric field gradients (EFG), and structure optimizations as implemented in the WIEN2k package for the structural and electronic characterizations of crystalline inorganic materials. Structure optimizations are essential for compounds whose structure was refined from usually less accurate powder diffraction data and provide a reliable assignment of the 27Al quadrupolar parameters to the aluminum sites in the studied compounds. The correlation between experimental and calculated EFG tensor elements leads to the proposition of a new value of the 27Al nuclear quadrupole moment Q(27Al) = 1.

Accurate heteronuclear J-coupling measurements in dilute spin systems using the multiple-quantum filtered J-resolved experiment.

A new solid-state MAS NMR experiment is proposed to accurately measure heteronuclear (19)F-(207)Pb J-coupling constants, even though these couplings are not visible on high speed (19)F 1D MAS spectra; in particular, we demonstrate that the J-resolved experiment combined with scalar multiple-quantum filtering considerably improves the resolution of J-multiplet patterns for dilute spin systems.

Multinuclear high-resolution NMR study of compounds from the ternary system NaF-CaF2-AlF3: from determination to modeling of NMR parameters.

27Al and 23Na NMR satellite transition spectroscopy and 3Q magic-angle-spinning spectra are recorded for three compounds from the ternary NaF-CaF2-AlF3 system. The quadrupolar frequency nuQ, asymmetry parameter etaQ, and isotropic chemical shift deltaiso are extracted from the spectrum reconstructions for five aluminum and four sodium sites. The quadrupolar parameters are calculated using the LAPW-based ab initio code WIEN2k.

Cluster models and ab initio calculations of (19)F NMR isotropic chemical shifts for inorganic fluorides.

(19)F NMR isotropic chemical shift (delta(iso)) calculations are performed in crystallized compounds using the GIAO method with the B3LYP hybrid functional at DFT level. Clusters centered on the studied fluorine atoms mimic the crystalline structures. The 6-311+G(d) basis set is chosen for the central fluorine atom, and the LanL2DZ basis set for the others.

Correlation between 19F environment and isotropic chemical shift in barium and calcium fluoroaluminates.

High-speed MAS (19)F NMR spectra are recorded and reconstructed for 10 compounds from BaF(2)-AlF(3) and CaF(2)-AlF(3) binary systems which leads to the determination of 77 isotropic (19)F chemical shifts in various environments. A first attribution of NMR lines is performed for 8 compounds using a superposition model as initially proposed by B. Bureau et al.

Electric field gradients in fluoride crystalline powders: correlation of NMR measurements with ab initio calculations.

Electric field gradients (EFG) of 23Na and 27Al in three model fluoride crystalline powders AlF3, Na3AlF6 and Na5Al3F14 were computed using the density functional based electronic structure code WIEN97 and compared to values derived from nuclear magnetic resonance (NMR). First, results of measurements of 23Na and 27Al quadrupolar parameters in AlF3, Na3AlF6 and Na5Al3F14 were revisited by using high-resolution solid-state NMR. To determine chemical shifts and quadrupolar parameters with a high precision, the experimental procedure involved magic angle spinning, satellite transition spectroscopy and multi-quanta techniques applied to the quadrupolar nuclei together with a computed reconstruction of the NMR spectra.

Structural insights into aluminum chlorofluoride (ACF).

The structure of the very strong solid Lewis acid aluminum chlorofluoride (ACF, AlCl(x)F(3-x), x = 0.05-0.3) was studied by IR, ESR, Cl K XANES, (19)F MAS NMR, and (27)Al SATRAS NMR spectroscopic methods and compared with amorphous aluminum fluoride conventionally prepared by dehydration of alpha-AlF(3) x 3H(2)O.

From crystalline to glassy gallium fluoride materials: an NMR study of 69Ga and 71Ga quadrupolar nuclei.

Owing to the implementation of acquisition techniques specific for nuclei with very large quadrupolar interaction (full shifted echo and variable offset cumulative spectra (VOCS)), NMR spectra of 69Ga and 71Ga are obtained in crystallised (PbGaF5, Pb3Ga2F12, Pb9Ga2F24 and CsZnGaF6) and glassy (PbF2-ZnF2-GaF3) gallium fluorides. Simulations of both static (full echo or VOCS) and 15 kHz MAS spectra allow to obtain consistent determinations of isotropic chemical shifts and very large quadrupolar parameters (nuQ up to 14 MHz). In the crystalline compounds whose structures are unknown, the number and the local symmetry of the different gallium sites are tentatively worked out.

CP-MAS 207Pb with 19F decoupling NMR spectroscopy: medium range investigation in fluoride materials.

The isotropic chemical shift of 207Pb is used to perform structural investigations of crystalline fluoride compounds (PbF2, Pb2ZnF6, PbGaF5, Pb3Ga2F12 and Pb9Ga2F24) and transition metal fluoride glasses (TMFG) of the PZG family (PbF2-ZnF2-GaF3). Using 207Pb Cross Polarisation Magic Angle Spinning (CP-MAS) NMR with 19F decoupling, it is shown that the isotropic chemical shift of 207Pb varies on a large scale (1000 ppm) and that the main changes of its value are not due to the nearest neighbour fluorines but may be related to the number of next nearest neighbour (nnn) Pb2+ ions. In this way, it is demonstrated that 207Pb chemical shift is an interesting probe to investigate medium range order in either crystalline or glassy fluoride systems.

From crystalline to glassy gallium fluoride materials: an NMR study of 69Ga and 71Ga quadrupolar nuclei.

Owing to the implementation of acquisition techniques specific for nuclei with very large quadrupolar interaction (full shifted echo and variable offset cumulative spectra (VOCS)), NMR spectra of 69Ga and 71Ga are obtained in crystallised (PbGaF5, Pb3Ga2F12, Pb9Ga2F24 and CsZnGaF6) and glassy (PbF2-ZnF2-GaF3) gallium fluorides. Simulations of both static (full echo or VOCS) and 15 kHz MAS spectra allow to obtain consistent determinations of isotropic chemical shifts and very large quadrupolar parameters (nu(Q) up to 14 MHz). In the crystalline compounds whose structures are unknown, the number and the local symmetry of the different gallium sites are tentatively worked out.