Magic Angle Spinning Techniques Research Articles

High-resolution proton magnetic resonance and catalytic studies concerning brønsted centers of amorphous Al 2O 3-SiO 2 solids

By application of the magic angle spinning (MAS) technique it was possible to observe highly resolved proton NMR spectra of the OH groups of amorphous silica-alumina. The spectra exhibit two lines at 2 and 7 ppm. The former line must be ascribed to non-acidic OH groups since it also occurs for silica and alumina. The latter line shows a maximum of intensity in the range of 20–30 wt% Al 2O 3. It must be due to acidic hydroxyl groups since the catalytic activity of the silica-aluminas measured by the cracking rate of cumene shows quantitatively the same behaviour with respect to the number of OH groups at 7 ppm.

NMR studies concerning the dehydroxylation of zeolites HY

By applying the magic-angle spinning technique to proton magnetic resonance of zeolites HY two or three different lines could be separated. Measurement

Spin–spin and spin-lattice contributions to the rotating frame relaxation of 13C in L-alanine

The spin-lattice relaxation times in both the Zeeman (TC1) and rotating (TC1ρ) frames were determined for three chemically distinct carbon atoms (13C) in polycrystalline L-alanine by combining crosspolarization and magic angle spinning techniques together with proton decoupling. The spin-lattice and spin–spin contributions to the experimentally measured TC*1ρ could be separated by an experiment in which the 13C spin-locking field was varied. The spin-lattice contributions (TC1ρ), which contain motional information, were determined to be 21.7, 23.4, and 138 ms for the Cα, CH3, and COO− carbons, respectively. The spin–spin contribution (TDCH) was found to be exponential, namely, (TDCH)−1 ∝exp(−2πνeCτD) in the low 13C spin-locking field. Therefore, the assumption of a Lorentzian correlation function for the proton dipolar fluctuations is adequate for L-alanine. Furthermore, the proton dipolar correlation times τD were found to be the same (31±1 μs) for all three carbons in L-alanine. The spin-lattice relaxation times in the Zeeman frame TC1 were determined to be 4.0 s, 38 ms, and 13 s for the Cα, CH3, and COO− carbons, respectively. The experimental values of TC1ρ and TC1 can be explained quantitatively by considering the internal rotations of the methyl and amino groups.

Chemical shift and quadrupole coupling of the 27Al NMR spectra of LiAIO 2 polymorphs

27Al chemical shift data of polycrystalline LiAlO 2 polymorphs, obtained from high field measurements in combination with magic-angle spinning techniques, have been used for the determination of the Al coordination in the α-, β-, and γ-phase. The β-phase was shown to have only tetrahedrally coordinated Al atoms. In addition quadrupole coupling data have been derived from analysis of low field NMR spectra of 27A1 in order to characterize the symmetry of the Al sites. The NMR results are discussed with regard to the crystal structure of the phases.

Investigations of polymer-supported complexes of platinum(II) by high-resolution solid-state phosphorus-31 NMR spectroscopy employing magic-angle spinning and cross-polarization techniques

Investigations of polymer-supported complexes of platinum(II) by high-resolution solid-state phosphorus-31 NMR spectroscopy employing magic-angle spinning and cross-polarization techniques

Detection of imogolite in soils using solid state 29Si NMR

High resolution solid state 29Si-NMR has recently been used to examine silicates, and synthetic and natural zeolites1–4. This has been possible through the use of dipolar decoupling, magicangle spinning and cross-polarization techniques which have enabled line narrowing and also considerable signal enhancement for 29Si nuclei in close proximity to protons. It has been found that isotropic 29Si chemical shifts in solids and solutions are generally similar and depend mainly on the degree of condensation of silicon–oxygen tetrahedra1 For silicates, increasing condensation from single (Q0, −66 to −72 p.p.m.) to double tetrahedra (Q1, −78 to −82 p.p.m.), to chains (Q2, −86 to −88 p.p.m.) and cyclic layered structures (Q3, −107 to −109 p.p.m.) leads to increasing diamagnetic shielding. In solid aluminosilicates, the 29Si chemical shift is sensitive to the substitution of aluminium. A further important point was that the 29Si linewidth in aluminosilicates is sensitive to the regularity of aluminium distribution in the lattice. Thus 29Si-NMR has obvious potential for the elucidation of the coordination of silicon in soils and mineral components. We report here the first 29Si-NMR study of the clay mineral imogolite, and show that 29Si-NMR is an excellent analytical technique for the identification of imogolite (or imogolite like materials, that is proto-imogolite) in clay fractions. The observed chemical shift of imogolite (−78 p.p.m.) is consistent with the proposal that imogolite is a tubular hydrated aluminosilicate in which silicon tetrahedra are isolated by coordination through oxygen with three aluminium atoms and one proton.

Carbon Functionalities in Amber

High-resolution nuclear magnetic resonance spectra of the carbon nuclei in powdered amber, obtained by using the techniques of magic angle spinning and cross polarization, provide detailed information about the types of carbon functionalities. The entire spectrum of Baltic amber (succinite) is identical for several samples. Baltic amber shows minor differences from Sicilian amber and drastic differences from Burmese, Romanian, and Bohemian ambers.

14N quadrupole effects in CP-MAS 13C NMR spectra of organic compounds in the solid state

The high-resolution solid-state 13C NMR spectra of 2,6-dimethyl-3-nitroaniline, glycylglycine, glycyl- l-alanine, and trimethylimidazole, were obtained by a combination of cross-polarization and magic-angle spinning techniques (CP-MAS). The 13C NMR lines of the carbon atoms bonded to nitrogen in these compounds showed a characteristic line broadening or asymmetric doublet patterns. The theoretical lineshapes of the 13C NMR lines arising from the carbon atoms bonded to nitrogen were calculated using the adiabatic approximation since the rate of change of the Zeeman-quadrupole Hamiltonian of nitrogen nucleus is very slow when compared to the speed of the spinning sample holder in the MAS experiment. In the calculation, an asymmetric quadrupole coupling tensor of nitrogen nucleus was considered. It was found that the calculated lineshapes are in good agreement with the experimentally observed lineshapes, and that the 14N quadrupole coupling tensor was responsible for the lineshapes of the carbon atoms bonded to nitrogen. The sign of the quadrupole coupling constants of the nitro and amino nitrogens in 2,6-dimethyl-3-nitroaniline were determined to be negative from an analysis of the lineshapes. In the case of trimethylimidazole, it was found that the 13C NMR signals of the C 4 and C 5 carbon atoms could also be assigned from a comparison of the theoretical and experimental lineshapes. This resolution of the C 4 and C 5 NMR resonances was possible because of the freezing-out of the tautomerism involving the NH bonds.

ChemInform Abstract: STUDIES OF PHOSPHORUS(III) LIGANDS AND THEIR COMPLEXES OF NICKEL(II), PALLADIUM(II), AND PLATINUM(II) IMMOBILIZED ON INSOLUBLE SUPPORTS BY HIGH‐RESOLUTION SOLID‐STATE PHOSPHORUS‐31 NMR USING MAGIC‐ANGLE SPINNING TECHNIQUES

Chemischer InformationsdienstVolume 13, Issue 18 Physical Organic Chemistry ChemInform Abstract: STUDIES OF PHOSPHORUS(III) LIGANDS AND THEIR COMPLEXES OF NICKEL(II), PALLADIUM(II), AND PLATINUM(II) IMMOBILIZED ON INSOLUBLE SUPPORTS BY HIGH-RESOLUTION SOLID-STATE PHOSPHORUS-31 NMR USING MAGIC-ANGLE SPINNING TECHNIQUES L. BEMI, L. BEMISearch for more papers by this authorH. C. CLARK, H. C. CLARKSearch for more papers by this authorJ. A. DAVIES, J. A. DAVIESSearch for more papers by this authorC. A. FYFE, C. A. FYFESearch for more papers by this authorR. E. WASYLISHEN, R. E. WASYLISHENSearch for more papers by this author L. BEMI, L. BEMISearch for more papers by this authorH. C. CLARK, H. C. CLARKSearch for more papers by this authorJ. A. DAVIES, J. A. DAVIESSearch for more papers by this authorC. A. FYFE, C. A. FYFESearch for more papers by this authorR. E. WASYLISHEN, R. E. WASYLISHENSearch for more papers by this author First published: May 4, 1982 https://doi.org/10.1002/chin.198218056AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume13, Issue18May 4, 1982 RelatedInformation

Nuclear magnetic resonance studies of ancient buried wood—II. Observations on the origin of coal from lignite to bituminous coal

Coalified logs ranging in age from Late Pennsylvania to Miocene and in rank from lignite B to bituminous coal were analyzed by 13C nuclear magnetic resonance (NMR) utilizing the cross-polarization, magic-angle spinning technique, as well as by infrared spectroscopy. The results of this study indicate that at least three major stages of coalification can be observed as wood gradually undergoes transformation to bituminous coal. The first stage involves hydrolysis and loss of cellulose from wood with retention and differential concentration of the resistant lignin. The second stage involves conversion of the lignin residues directly to coalified wood of lignitic rank, during which the oxygen content of intermediate diagenetic products remains constant as the hydrogen content and the carbon content increases. These changes are thought to involve loss of methoxyl groups, water, and C3 side chains from the lignin. In the third major stage of coalification, the coalified wood increases in rank to subbituminous and bituminous coal; during this stage the oxygen content decreases, hydrogen remains constant, and the carbon content increases. These changes are thought to result from loss of soluble humic acids that are rich in oxygen and that are mobilized during compaction and dewatering. Relatively resistant resinous substances are differentially concentrated in the coal during this stage. The hypothesis that humic acids are formed as mobile by-products of the coalification of lignin and function only as vehicles for removal of oxygen represents a dramatic departure from commonly accepted views that they are relatively low-molecular-weight intermediates formed during the degradation of lignin that then condense to form high-molecular-weight coal structures.

The detection and characterization of surface immobilized phosphine ligands and transition metal catalysts by high resolution 31P solid state NMR using magic angle spinning techniques

High-power proton decoupling, cross-polarization and magic angle spinning techniques have been used to obtain high resolution 31P NMR spectra of solid cis-[PtCl 2(PR 3) 2] (PR 3 = PPh 2Me (I); PR 3 = PPh 2(CH 2) 2Si(OEt) 3 (II) complexes. Solid-state effects result in non-equivalent 31P shieldings within a single solid sample and the magnitude of scalar couplings are comparable to those obtained in solution. Reaction of II with silica or glass surfaces yielded an immobilized complex whose geometry was determined by these methods. The utility of various preparative routes to phosphine-linked immobilized transition metal complexes on silica and glass surfaces have been evaluated.

Studies of phosphorus(III) ligands and their complexes of nickel(II), palladium(II), and platinum(II) immobilized on insoluble supports by high-resolution solid-state phosphorus-31 NMR using magic-angle spinning techniques

Studies of phosphorus(III) ligands and their complexes of nickel(II), palladium(II), and platinum(II) immobilized on insoluble supports by high-resolution solid-state phosphorus-31 NMR using magic-angle spinning techniques

Absence of Knight-Sheft in the Metallic State of Polyacetylene

Abstract NMR spectra on 18C of cis-(CH)x have been recorded using the magic angle spinning technique. Inspite of doping with AsF5 up to a level of ∼ 7at%, (CH)x does not convert to the trans modification. No Knight shift or other line shift is observed up to this dopant concentrtion. Above 7at% a line shift of about 30 ppm is found. To extend the soliton model to cis-(CH)x bi-solitons or bi-polarons are proposed.

Investigation of poly(arylenevinylene)s, 24. High‐resolution solid‐state 13C NMR spectroscopy of poly(1,4‐phenylenevinylene)s

AbstractHigh‐resolution 13C NMR spectra of solid poly(1,4‐phenylenevinylene), poly(1,4‐phenylene‐1,2‐diphenylvinylene) and of three related, substituted polymers (CN, OCH3, O) were obtained with a combined technique of heteronuclear decoupling, cross‐polarization and magic angle spinning. The reported chemical shifts were assigned by means of solid model compounds (trans‐stilbene, trans, trans‐1,4‐distyrylbenzene, tetraphenylethylene). Utilizing the high sensitivity of 13C NMR chemical shifts to chemical structure, this method is applied to structure confirmation, the determination of sp3‐defects in poly(phenylenevinylene)s PPV, and the determination of sterical and electronical effects of phenyl and phenylene groups.

Micro- and macroconformation of macromolecules

SUMMARY By applying high resolution solid state 13C-NMR with proton enhancement and with magic angle spinning technique it is demonstrated that the rotational states in semicrystalline polymers may be analyzed for the crystalline as well as for the amorphous phase. In erythrodiisotact ic poly(1,2-dimethyltetramethylene) the signals of the chemically different nuclei could be distinguished in the crystalline and in the amorphous regions. The interpretation of the solid state spectrum is consistent with the solution spectrum of the polymer and with that of the analogous low molecular weight compound, meso 4,5-dimethyloctane, under slow exchange conditions. It is concluded that the crystalline parts of the macromolecular chain exhibit g+aaag-aaag+.., conformation (gauches for the CH-CH bond), which is in agreement with the X-ray structure analysis by NATTA et al. Another stable conformation derived from semiempirical atomistic calculations could be excluded for the crystalline phase. An estimation of the conformational balance in the amorphous state has been achieved by comparing the relevant shift data of the solid state erythrodiisotact ic poly(1,2-dimethyltetramethylene) with those occuring in the fast exchange spectrum measured in solution.

High resolution solid state 13C NMR spectra of carbons bonded to nitrogen in a sample spinning at the magic angle

High resolution solid state 13C NMR spectra of amino acids and nitrile compounds have been obtained by a combination of cross-polarization, dipolar decoupling, and magic angle spinning techniques (CP–MAS). The resonances of Cα and cyano carbons in the observed 13C spectra show asymmetric doublet patterns. This problem has been treated by using the adiabatic approximation since the 14N quadrupole interaction is much larger than the spinning frequency. Theoretical spectra have been simulated for these carbons and they show very good agreement with experimental observations.

Absence of Knight-shift in the metallic state of polyacetylene

NMR spectra on 13C of polyacetylene have been recorded using the magic angle spinning technique. Despite the high metallic conductivity of AsF 5-doped samples in the doping range from 1–7 %, no Knight-shift can be detected. Only for concentrations above 7 %, far beyond the insulator-metal transition, a Knight-shift of about 30 ppm and strong line broadening is observed. This absence of the Knight-shift below the critical concentration of 7 % is in good agreement with the previously reported lack of Pauli-paramagnetism and hence confirms the existence of a novel mechanism of electrical conductivity with spinless charge carriers in the doping range from 1 to 7 %.

Cabbon-13 cross polarization with magic angle spinning nuclear magnetic resonance spectroscopy of organosilanes bonded to silica surfaces

High-resolution 13C-n.m.r. spectra were obtained of organosilane moieties chemically bound to the surface of silica. Techniques of cross polarization and magic angle spinning were employed. The spectra clearly confirmed some structures bound to the surface and showed that others were not as expected.

Application of High-Resolution 13C NMR Spectroscopy Using Magic Angle Spinning Techniques to the Direct Investigation of Solid Cured Phenolic Resins

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTApplication of High-Resolution 13C NMR Spectroscopy Using Magic Angle Spinning Techniques to the Direct Investigation of Solid Cured Phenolic ResinsC. A. Fyfe, A. Rudin, and W. TchirCite this: Macromolecules 1980, 13, 5, 1320–1322Publication Date (Print):September 1, 1980Publication History Published online1 May 2002Published inissue 1 September 1980https://doi.org/10.1021/ma60077a059RIGHTS & PERMISSIONSArticle Views140Altmetric-Citations44LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (368 KB) Get e-Alerts Get e-Alerts

Use of solid-state 13C NMR in structural studies of humic acids and humin from Holocene sediments

13C NMR spectra of solid humic substances in Holocene sediments have been obtained using cross polarization with magic-angle sample spinning techniques. The results demonstrate that this technique holds great promise for structural characterizations of complex macromolecular substances such as humin and humic acids. Quantifiable distinctions can be made between structural features of aquatic and terrestrial humic substances. The aliphatic carbons of the humic substances are dominant components suggestive of input from lipid-like materials. An interesting resemblance is also noted between terrestrial humic acid and humin spectra.