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Journal ArticleDOI

NMR nomenclature. Nuclear spin properties and conventions for chemical shifts(IUPAC Recommendations 2001)

01 Jan 2001-Pure and Applied Chemistry (International Union of Pure and Applied Chemistry)-Vol. 73, Iss: 11, pp 1795-1818
TL;DR: In this paper, a unified scale is recommended for reporting the NMR chemical shifts of all nuclei relative to the 1 H resonance of tetramethylsilane (TMS) in dilute solution (volume fraction, φ < 1%).
Abstract: A unified scale is recommended for reporting the NMR chemical shifts of all nuclei relative to the 1 H resonance of tetramethylsilane (TMS The unified scale is designed to provide a precise ratio, Ξ, of the resonance frequency of a given nuclide to that of the primary reference, the 1 H resonance of TMS in dilute solution (volume fraction, φ < 1%) in chloroform. Referencing procedures are discussed, including matters of practical application of the unified scale. Special attention is paid to recommended reference samples, and values of Ξ for secondary references on the unified scale are listed, many of which are the results of new measurements. Some earlier recommendations relating to the reporting of chemical shifts are endorsed. The chemical shift, δ, is redefined to avoid previous ambiguities but to leave practical usage unchanged. Relations between the unified scale and recently published recommendations for referencing in aqueous solutions (for specific use in biochemical work) are discussed, as well as the special effects of working in the solid state with magic-angle spinning. In all, nine new recommendations relating to chemical shifts are made. Standardized nuclear spin data are also presented in tabular form for the stable (and some unstable) isotopes of all elements with nonzero quantum numbers. The information given includes quantum numbers, isotopic abundances, magnetic moments, magnetogyric ratios and receptivities, together with quadrupole moments and line-width factors where appropriate.
Citations
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Journal ArticleDOI
TL;DR: A prototype phosphor-converted LED (pc-LED), employing Sr[LiAl3N4]:Eu(2+) as the red-emitting component, already shows an increase of 14% in luminous efficacy compared with a commercially available high colour rendering index (CRI) LED, together with an excellent colour rendition.
Abstract: To facilitate the next generation of high-power white-light-emitting diodes (white LEDs), the discovery of more efficient red-emitting phosphor materials is essential. In this regard, the hardly explored compound class of nitridoaluminates affords a new material with superior luminescence properties. Doped with Eu(2+), Sr[LiAl3N4] emerged as a new high-performance narrow-band red-emitting phosphor material, which can efficiently be excited by GaN-based blue LEDs. Owing to the highly efficient red emission at λ(max) ~ 650 nm with a full-width at half-maximum of ~1,180 cm(-1) (~50 nm) that shows only very low thermal quenching (>95% relative to the quantum efficiency at 200 °C), a prototype phosphor-converted LED (pc-LED), employing Sr[LiAl3N4]:Eu(2+) as the red-emitting component, already shows an increase of 14% in luminous efficacy compared with a commercially available high colour rendering index (CRI) LED, together with an excellent colour rendition (R(a)8 = 91, R9 = 57). Therefore, we predict great potential for industrial applications in high-power white pc-LEDs.

1,144 citations

Journal ArticleDOI
TL;DR: Solid state and liquid phase NMR shifts obtained by magic angle spinning with external referencing agree with those measured using typical solution NMR hardware with the sample tube aligned with the applied field as long as magnetic susceptibility corrections and solvent shifts are taken into account.

759 citations

Journal ArticleDOI
25 Apr 2014-Science
TL;DR: A strategy for eliminating the racemic background reaction in asymmetric [2 + 2] photocycloadditions of α,β-unsaturated ketones to the corresponding cyclobutanes is described by using a dual-catalyst system consisting of a visible light–absorbing transition-metal photocatalyst and a stereocontrolling Lewis acid cocatalyst.
Abstract: In contrast to the wealth of catalytic systems that are available to control the stereochemistry of thermally promoted cycloadditions, few similarly effective methods exist for the stereocontrol of photochemical cycloadditions. A major unsolved challenge in the design of enantioselective catalytic photocycloaddition reactions has been the difficulty of controlling racemic background reactions that occur by direct photoexcitation of substrates while unbound to catalyst. Here, we describe a strategy for eliminating the racemic background reaction in asymmetric [2 + 2] photocycloadditions of α,β-unsaturated ketones to the corresponding cyclobutanes by using a dual-catalyst system consisting of a visible light-absorbing transition-metal photocatalyst and a stereocontrolling Lewis acid cocatalyst. The independence of these two catalysts enables broader scope, greater stereochemical flexibility, and better efficiency than previously reported methods for enantioselective photochemical cycloadditions.

426 citations

Journal ArticleDOI
TL;DR: In this article, the impact of pyrolysis temperature on two important soil hydrologic properties, namely field capacity and hydrophobicity, was investigated. And they found that both properties can be controlled by choice of pyrotechnic temperature, and that 400°C-600°C produced biochars with the most desirable hydrological properties.
Abstract: Adding charcoal to soil (biochar soil amendment) can sequester carbon and improve soil performance, although the extent and exact mechanisms of soil improvement are not clear. Additionally, biochar properties can vary significantly with production conditions. Here we characterize the impact of pyrolysis temperature on two important soil hydrologic properties: field capacity and hydrophobicity. We show that pure biochar exhibits a wide range in both properties depending on feedstock and pyrolysis conditions. We find that both properties can be controlled by choice of pyrolysis temperature; 400 °C–600 °C produced biochars with the most desirable hydrological properties (peak field capacity and minimum hydrophobicity). Further, we show that hydrophobicity is strongly correlated ( R 2 = 0.87; p

419 citations

Journal ArticleDOI
TL;DR: In this article, an effort has been made to review the available literature information on the DA for the two biopolymers by different techniques of nuclear magnetic resonance, NMR (1H NMR, 13C NMR and 15N NMR) spectroscopy.

260 citations

References
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Book
01 Jan 1996
TL;DR: Encyclopedia of nuclear magnetic resonance, Encyclopedia of Nuclear Magnetic Resonance (ENM) as discussed by the authors, is an encyclopedia of nuclear magnetism and magnetic resonance (EMR) research.
Abstract: Encyclopedia of nuclear magnetic resonance , Encyclopedia of nuclear magnetic resonance , کتابخانه دیجیتال جندی شاپور اهواز

1,379 citations


"NMR nomenclature. Nuclear spin prop..." refers background in this paper

  • ...A version of Tables 1–3 has been published [7]....

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Journal ArticleDOI
TL;DR: The recommendations presented here are designed to support easier communication of NMR data and NMR structures of proteins and nucleic acids through unified nomenclature and reporting standards.

391 citations


"NMR nomenclature. Nuclear spin prop..." refers background or methods in this paper

  • ...Recently, however, conventions for chemical shifts of five nuclei of wide biochemical interest have been included in “Recommendations for the presentation of NMR structures of proteins and nuclei acids” [4] by Commission I....

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  • ...} When DSS is used as a reference, it has been recommended [4] that 1H chemical shifts be denoted by the symbol δDSS to distinguish them from those referenced to TMS....

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  • ...This recommendation is in line with the “Recommendations for presentation of NMR structures of proteins and nucleic acids”, recently promulgated [4] by IUPAC in conjunction with the International Union of Biochemistry and Molecular Biology and the International Union of Pure and Applied Biophysics, which include recommended Ξ values for several nuclei of importance in such studies for aqueous solutions, but which uses the proton resonance of DSS as the primary standard because of its solubility in water (see Section 3....

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Journal ArticleDOI
TL;DR: In this article, the authors present a list of symbols (using Roman or Greek characters) to be used for quantities relevant to nuclear magnetic resonance (NMR) spectroscopy, in order to reduce the variations in the usage of symbols for the same physical quantity.
Abstract: NMR is now frequently the technique of choice for the determination of chemical structure in solution. Its uses also span structure in solids and mobility at the molecular level in all phases. The research literature in the subject is vast and ever-increasing. Unfortunately, many articles do not contain sufficient information for experiments to be repeated elsewhere, and there are many variations in the usage of symbols for the same physical quantity. It is the aim of the present recommendations to provide simple check-lists that will enable such problems to be minimised in a way that is consistent with general IUPAC formulation. The area of medical NMR and imaging is not specifically addressed in these recommendations, which are principally aimed at the mainstream use of NMR by chemists (of all sub-disciplines) and by many physicists, biologists, materials scientists and geologists etc. working with NMR. The document presents recommended notation for use in journal publications involving a significant contribution of nuclear magnetic resonance (NMR) spectroscopy. The recommendations are in two parts: (1) Experimental parameters which should be listed so that the work in question can be repeated elsewhere. (2) A list of symbols (using Roman or Greek characters) to be used for quantities relevant to NMR.

26 citations

Journal ArticleDOI

22 citations

Journal ArticleDOI
TL;DR: The second edition of this useful compendium of international agreements and recommended practice on physical quantities, units and symbols was published by the Symbols Committee of the Royal Society in 1975 as mentioned in this paper.
Abstract: Symbols Committee of the Royal Society London: Royal Society 1975 pp 56 price £1 A completely revised second edition of this useful compendium of international agreements and recommended practice on physical quantities, units and symbols. Apart from updating to the end of 1974 (eg the inclusion of the units becquerel and gray and the prefixes peta ≡1013 and exa ≡ 1018) there are several changes of emphasis.

2 citations


"NMR nomenclature. Nuclear spin prop..." refers methods in this paper

  • ...Many of the data in Tables 1–3 have been taken from the IUPAC “Green Book” [6], but additional information is included (particularly on resonance frequencies and quadrupole moments)....

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