Structure solid state NMR

Keywords Dipolar recoupling Dynamics Protein structure Solid-state NMR... 

Byrn, S. R., Sutton, R A., Tobias, B., Frye, J. and Main, P. (1988). The crystal structure solid state NMR spectra and oxygen reactivity of five crystal forms of prednisolone tert-butylacetate. J. Am. Chem. Soc., 110, 1609-14. [135]... 

Keywords Bone Apatite Structure Solid-state NMR Cross-polarization... 

SR Byrn, PA Sutton, B Tobias, J Frye, P Main. Crystal structure, solid-state NMR spectra, and oxygen reactivity of five crystal forms of prednisolone ierf-butylace-tate. J Am Chem Soc 110 1609-1614, 1988. 

S. R. Byrn, P. A. Sutton, B. Tobias, J. Frye, and P. Main,/. Am. Chem. Soc., 110,1609 (1988). The Crystal Structure, Solid-State NMR Spectra, and Oxygen Reactivity of Five Crystal Forms of Prednisolone tert-Butylacetate. 

Nuclear magnetic resonance (NMR)—Unlike other structural techniques, such as powder and single-crystal x-ray and neutron diffraction, which characterize the "long-range" order, giving an average view of a structure, solid-state NMR probes the local environment of a particular nucleus and, therefore, is highly suited to study amorphous or disordered materials, such as modified LDH. An extensive review of NMR studies related to both the structure and dynamics in LDH materials was reported by Rocha [11]. Herein, we concentrate on site-specific information available from the H and Al solid-state NMR. 

Structural and Chemical Information from Solid State NMR Line Shapes... 

Solid state NMR is a relatively recent spectroscopic technique that can be used to uniquely identify and quantitate crystalline phases in bulk materials and at surfaces and interfaces. While NMR resembles X-ray diffraction in this capacity, it has the additional advantage of being element-selective and inherently quantitative. Since the signal observed is a direct reflection of the local environment of the element under smdy, NMR can also provide structural insights on a molecularlevel. Thus, information about coordination numbers, local symmetry, and internuclear bond distances is readily available. This feature is particularly usefrd in the structural analysis of highly disordered, amorphous, and compositionally complex systems, where diffraction techniques and other spectroscopies (IR, Raman, EXAFS) often fail. 

Due to these virtues, solid state NMR is finding increasing use in the structural analysis of polymers, ceramics and glasses, composites, catalysts, and surfaces. 

The followmg types of studies will not be presented individually but may have contnbuted supportmg data to coverage by compound type conformational analyses [23 24, 25, 26 27], fluoropolymers [28, 29, 30 31, 32], solid-state NMR [ii], and solvent effects [34 35, 36, 37] Many excellent articles with m-depth NMR interpretation of one specific compound or of a small, structurally related group of compounds can be found in the chemical hterature A few of these, not incorporated elsewhere in this secUon are referenced here carbonyl fluondes [JS 39 40], fluoropropanes [41 42, 43], fluorocyclopropanes [44, 45 46], fluorobutanes [47], perfluorocyclobutanone [48], fluorohexanes [49], and vinyl fluondes [50, 51 52, 53, 54]... 

As already explained in the relevant section, the use of X-ray crystallography (Section V,D,2), the possibility to determine the molecular structure from powder diffraction without the need to obtain monocrystals, and the many variants of solid-state NMR (Section VI,F) have profoundly enhanced the study of tautomerism in the solid state. 

Generation of reaction networks with RAIN resonance structures and tautomerism Solid-state NMR studies of reversible 1,5-H shifts Tautomeric equilibria (AMI, MNDO, PM3)... 

Styrene-butadiene rubber (SBR) is the most widely used synthetic rubber. It can be produced by the copolymerization of butadiene (= 75%) and styrene (=25%) using free radical initiators. A random copolymer is obtained. The micro structure of the polymer is 60-68% trans, 14-19% cis, and 17-21% 1,2-. Wet methods are normally used to characterize polybutadiene polymers and copolymers. Solid state NMR provides a more convenient way to determine the polymer micro structure. ... 

The CP/MAS NMR spectra are an important source of information regarding the structure of cellulose and its polymorphos. A number of groups have investigated these spectra 11 15) and also reviews on the subject have been published 16 17>. For an orientation in the field Table 1 shows the most important features of the solid-state NMR spectra of cellulose I, II and IV and in Fig. 3 the numeration of the carbon atoms of the cellulose basic unit is given. It is evident that the polymorphs... 

It is evident that the solid-state NMR data combined with vibration spectra call for a reasessment of earlier views of cellulose I and II. Furthermore, earlier interpretations of diffractometric data that ignore differences in molecular conformations will, according to Atalla 191 be insensitive to subtle structural variations which are central to the phenomena of polymorphy and so clearly indicated by the NMR... 

The incorporation of water in the structure of cellulose influences. Upon the hydrogen bond structure of the macromolecule. A great deal of work has been done in this area. Calorimetric methods have been invaluable in helping to solve the problem 23 It is, however evident that solid-state NMR spectroscopy may also give valuable information. 

One of the most important areas of application of the solid-state NMR technique is the investigation of the structures of cross-linked amorphous materials in cases where X-ray diffraction technqiues are not applicable. Polymeric resins are one such important class of materials. A lot of work has been done in this area by several investigators 36,37 38 since the beginning of the 80. Some solid-state NMR data of phenolic resins are presented in Fig. 10. Comparison with liquid state data for... 

Fig. 12. Tentative structure of lignin according to Adler together with typical solid state NMR signals of its carbon atoms...

Eckert H,Elbers S,Epping JD, Janssen M, Kalwei M, StrojekW, Voigt U (2005) Dipolar Solid State NMR Approaches Towards Medium-Range Structure in Oxide Glasses. 246 195-233... 

A bridged carbocation with a two-electron, three-centre bond was proposed as early as 1939 (Nevell et al., 1939) for the 2-norbornyl cation [lO ] as a reactive intermediate in the solvolysis of 2-norbornyl system (see also Winstein and Trifan, 1949). It has now been isolated as the SbFe salt and the bridged structure is accounted for using solid-state nmr studies... 

Not much needs to be said on these glasses, except that one, G-235 (Table 5.8) has been subjected to solid state NMR (Ellison Warrens, 1987). It would appear that aluminium is mainly in tetrahedral coordination with some octahedral and pentahedral coordination and that the structural units are mainly Q (lAl) and Q (2A1). 

In the 1970s the structure and dynamics of lipid bilayer membranes were extensively investigated by NMR. The principles of the NMR spectroscopy applied to the study of biomembranes are reviewed in Ref. 5, together with the fruitful achievements in the early stage. In the 1980s the NMR biomembrane research was carried out mainly by applying the solid-state NMR techniques [6-11]. Generally, the solid-state spectra are of low reso-... 

Numerous compounds of Cd with mono- and difunctional carboxylic acids have been prepared and studied. Special ll3Cd solid-state NMR studies on single crystals of some simple Cd carboxylates have been reported, with a short review of the structural chemistry of these compounds.270,271... 

No solid state NMR experiment is able to obtain spectra comparable to those routinely recorded in the liquid state. Thus multiplets become broad singlets and, if close together, overlap to give a broad signal envelope . While the differentiation of aromatic and aliphatic protons is simple, the information available is, from the point of view of structure determination, very limited. Thus we shall not provide an example. 

This is where solid state NMR starts to come into its own. Molecules which form crystals can be studied routinely by X-ray crystallography, which gives exact structural information. This information is limited in value, however,... 

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