Dipolar Coupling Information in Multispin Systems: Application of a Compensated REDOR NMR Approach to Inorganic Phosphates

Chan, Jerry C. C.; Eckert, Hellmut

doi:10.1006/jmre.2000.2191

Cited by 157 publications

(153 citation statements)

References 34 publications

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“…An isotopically enriched sample of SiBN 3 C ceramic was prepared from the single-molecule precursor TADB (Cl 3 Si(NH)BCl 2 ) polymerized with 99 % 13 C, 15 N methylamine (Sigma Aldrich, 13 CH 3 15 NH 2 ). All steps were performed under an argon atmosphere.…”

Section: Methodsmentioning

confidence: 99%

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Observation of Direct Bonds between Carbon and Nitrogen in Si‐B‐N‐C Ceramic after Pyrolysis at 1400 °C

2008

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Section: Methodsmentioning

confidence: 99%

“…This analysis was performed by using the approach developed by Eckert and co-workers. [14,15] The advantage of the use of M 2 is that one can easily check whether a large number of nitrogen atoms without a direct bond to carbon could perhaps also account for the shape of the experimental REDOR curve. The results are shown in Figure 3.…”

mentioning

confidence: 99%

Observation of Direct Bonds between Carbon and Nitrogen in Si‐B‐N‐C Ceramic after Pyrolysis at 1400 °C

2008

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“…Following a previously reported procedure, 35,36 the data within the initial range ΔS/S 0 < 0.2 can be approximated by a parabolic function, whose curvature is proportional to M 2 ( 23 Na{ 31 P}). 36 Figure 14 and Table 10 summarize these data.…”

Section: Na{mentioning

confidence: 99%

Mixed Network Former Effects in Oxide Glasses: Spectroscopic Studies in the System (M₂O)_1/3[(Ge₂O₄)_x(P₂O₅)_1–x]_2/3

Behrends

Eckert

2014

J. Phys. Chem. C

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The structure of mixed-network former glasses in the system (M2O)0.33[(Ge2O4) x (P2O5)1–x ]0.67.(M = Na, K) has been studied by 31P and 23Na high-resolution and dipolar solid state nuclear magnetic resonance (NMR) techniques, O-1s X-ray photoelectron spectroscopy, and Raman spectroscopy. Using an iterative fitting procedure, a quantitative structural model has been developed that is consistent with all of the experimental data and which provides a detailed description of network connectivities, network modification processes, and spatial cation distributions. Formation of heteroatomic P–O–Ge linkages is generally preferred over homoatomic P–O–P and Ge–O–Ge linkages, as shown by a detailed comparison with a random linkage model. An exception occurs in glasses with low germanium contents (x = 0.2) where a pronounced nonlinear dependence of the glass transition temperature on x can be related to a cross-linking of the sodium ultraphosphate network by fully polymerized germanium species, possibly including also 5- and 6-fold coordination states. At higher x values, the Ge component is modified as well, however, the fraction of anionic nonbridging oxygen atoms bound to germanium is always lower than expected for proportional modifier sharing between both network formers. Rather, the phosphate component is preferentially modified by the cations, leading to the formation of P(1) units at high x values. Consequently, the local coordination of the cations is dominated by phosphorus, as is clearly evident from the 23Na{31P} rotational echo double resonance (REDOR) results. This preferred association, combined with the formation of P(1) units, results in partially clustered cation distributions, which can be detected by 23Na spin echo decay spectroscopy. Finally, the joint interpretation of all of the data from NMR, Raman, XPS, and thermal analysis measurements offers indirect evidence for the formation of higher germanium coordination states in this glass system.

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“…The quantitative REDOR measurements can be sensitively influenced by some experimental conditions, such as finite pulse length, pulse imperfections, and spinning stability. [24] We have also found that the application of multispin REDOR can be prohibitively time consuming for examining defect-level concentrations, since the relative error at short evolution time (i.e. S/S 0 < 0.3) is much larger than that at long evolution time.…”

mentioning

confidence: 97%

NMR spectroscopy of citrate in solids: cross‐polarization kinetics in weakly coupled systems

Feng¹,

Lee²,

Kubicki³

et al. 2008

Magnetic Reson in Chemistry

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Solid-state NMR spectroscopy is a potentially powerful method for obtaining molecular level structural information crucial for understanding the specific relationship between calcite crystals and occluded organic molecules that are important in biomineralization and biomimetic materials. In this work, a method is developed based on cross-polarization/magic angle spinning (CP/MAS) NMR to measure the heteronuclear distances and obtain structural information for large intracrystalline citrate defects in a synthetic calcite/citrate composite. Using compounds with well-characterized crystal structures, Mg(II) citrate and Sr(II) citrate, a correlation is established between T(IS), the CP time, and M(2) (IS), the van Vleck heteronuclear dipolar second moment, which contains distance and structural information. This correlation is supported by peak assignments obtained from calculations of the (13)C chemical shifts for crystalline Mg(II) citrate. On the basis of T(IS) (-1) versus M(2) (IS) correlation, measurement of T(IS) for carbonate ions associated with citrate defects in a calcite((13)C-enriched)/citrate coprecipitate yields an estimate for the distance between citrate and the nearest carbonate carbon that indicates close spatial proximity and provides useful constraints for future computational study. The applicability of T(IS) (-1) versus M(2) (IS) correlations to other weakly coupled spin-1/2 systems is discussed in terms of the effects of (1)H homonuclear dipolar coupling, using the CP kinetics of Zn(II) dihydroxybenzoate and kaolinite for comparison. The results suggest a limited range of correlation constants and indicate that quantitative information can be obtained from CP/MAS kinetics obtained under similar experimental conditions.

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Dipolar Coupling Information in Multispin Systems: Application of a Compensated REDOR NMR Approach to Inorganic Phosphates

Cited by 157 publications

References 34 publications

Observation of Direct Bonds between Carbon and Nitrogen in Si‐B‐N‐C Ceramic after Pyrolysis at 1400 °C

Observation of Direct Bonds between Carbon and Nitrogen in Si‐B‐N‐C Ceramic after Pyrolysis at 1400 °C

Mixed Network Former Effects in Oxide Glasses: Spectroscopic Studies in the System (M₂O)_1/3[(Ge₂O₄)_x(P₂O₅)_1–x]_2/3

NMR spectroscopy of citrate in solids: cross‐polarization kinetics in weakly coupled systems

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Dipolar Coupling Information in Multispin Systems: Application of a Compensated REDOR NMR Approach to Inorganic Phosphates

Cited by 157 publications

References 34 publications

Observation of Direct Bonds between Carbon and Nitrogen in Si‐B‐N‐C Ceramic after Pyrolysis at 1400 °C

Observation of Direct Bonds between Carbon and Nitrogen in Si‐B‐N‐C Ceramic after Pyrolysis at 1400 °C

Mixed Network Former Effects in Oxide Glasses: Spectroscopic Studies in the System (M2O)1/3[(Ge2O4)x(P2O5)1–x]2/3

NMR spectroscopy of citrate in solids: cross‐polarization kinetics in weakly coupled systems

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Mixed Network Former Effects in Oxide Glasses: Spectroscopic Studies in the System (M₂O)_1/3[(Ge₂O₄)_x(P₂O₅)_1–x]_2/3