Solid-state NMR correlation

In the case of albendazole (36) (Scheme 27) ultrafast MAS, solid-state NMR spectroscopy, together with powder X-ray diffraction, thermal analysis, and Fourier transform IR spectroscopy were performed on polycrystalline samples of two solids in order to fuUy characterize and distinguish the two forms 36a and 36b. High-resolution 2D H, and together with 2D H/ H single quantum/single quantum, H/ H single quantum/double quantum, and chemical shift correlation solid-state NMR experi-... 

G.P. Holland, M.S. Creager, J.E. Jenkins, R.V. Lewis, J.L. Yarger, Determining secondary structure in spider dragline silk by carbon-carbon correlation solid-state NMR spectroscopy,. Am. Chem. Soc. 130 (2008) 9871—9877. 

Mao, K., and Pruski, M. Directly and indirectly detected through-bond heteronu-clear correlation solid-state NMR spectroscopy under fast MAS.. /. Mam. Reson. 2009 201 165-174. 

This chapter simnnarizes the interactions that affect the spectrum, describes the type of equipment needed and the perfomiance that is required for specific experiments. As well as describing the basic experiments used in solid-state NMR, and the more advanced teclmiques used for distance measurement and correlation, some emphasis is given to nuclei with spin / > dsince the study of these is most different from liquid-state NMR. 

In addition to sample rotation, a particular solid state NMR experiment is further characterized by the pulse sequence used. As in solution NMR, a multitude of such sequences exist for solids many exploit through-space dipolar couplings for either signal enhancement, spectral assignment, interauclear distance determination or full correlation of the spectra of different nuclei. The most commonly applied solid state NMR experiments are concerned with the measurement of spectra in which intensities relate to the numbers of spins in different environments and the resonance frequencies are dominated by isotropic chemical shifts, much like NMR spectra of solutions. Even so, there is considerable room for useful elaboration the observed signal may be obtained by direct excitation, cross polarization from other nuclei or other means, and irradiation may be applied during observation or in echo periods prior to... 

The molecular structure of the amyloid fibrils formed by fragment 105-115 of transthyretin (TTR10sns, YTIAALLSPTS) has been characterized by solid-state NMR. The fibril backbone structure was first established based on the TALOS analysis of the 15N and 13C chemical shifts [89]. Using the correlation experiments of Hn(0-N(0—CV-H0 , Ha(0-Ca(0-N(i.+1)-HN(i+1), and N -Tco-N, a total of 41 constraints on 19 backbone torsion angles have been obtained in a... 

Crosslinked polymer networks formed from multifunctional acrylates are completely insoluble. Consequently, solid-state nuclear magnetic resonance (NMR) spectroscopy becomes an attractive method to determine the degree of crosslinking of such polymers (1-4). Solid-state NMR spectroscopy has been used to study the homopolymerization kinetics of various diacrylates and to distinguish between constrained and unconstrained, or unreacted double bonds in polymers (5,6). Solid-state NMR techniques can also be used to determine the domain sizes of different polymer phases and to determine the presence of microgels within a poly multiacrylate sample (7). The results of solid-state NMR experiments have also been correlated to dynamic mechanical analysis measurements of the glass transition (1,8,9) of various polydiacrylates. 

Through a combination of X-ray crystallography and solid-state NMR studies, they were able to correlate chromic transitions with motion, and an increase in disorder within the backbone of the polymer [1]. As the temperature increased, so did disorder within the polymer, resulting in a blue-shift of the UV-vis spectra (Fig. 4). 

Since the discovery of the nuclear Overhauser effect (NOE, see previous section) [4, 5] and scalar coupling constants [36, 37] decades ago, NMR-derived structure calculations of biomolecules largely depended on the measurement of these two parameters [38]. Recently it became possible to use cross-correlated relaxation (CCR) to directly measure angles between bond vectors [39] (see also Chapt 7). In addition, residual dipolar couplings of weakly aligned molecules were discovered to measure the orientation of bond vectors relative to the alignment tensor (see Sect 16.5). Measurement of cross-correlated relaxation was described experimentally earlier for homonuclear cases [40, 41] and is widely used in solid-state NMR [42 14]. 

Solid state NMR has been used to study polymers of various classes over the past several years. In particular, the technique has been used to study curing reactions in epoxies (12). polyimides (1), and acetylenic terminated sulfones (13). The ability to observe the evolution of the carbons of the reacting species has been clearly shown to provide valuable information which has been difficult or impossible to obtain with other techniques. The use of 13C solid state NMR techniques is essential for the understanding of curing reactions in high temperature polymers in order to be able to correlate the reaction chemistry with the structural and resulting physical properties. 

Monolayer coverage of vanadium oxide on tin oxide support was determined by a simple method of low temperature oxygen chemisorption and was supported by solid-state NMR and ESR techniques. These results clearly indicate the completion of a monolayer formation at about 3.2 wt.% V2O5 on tin oxide support (30 m g" surface area). The oxygen uptake capacity of the catalysts directly correlates with their catalytic activity for the partial oxidation of methanol confirming that the sites responsible for oxygen chemisorption and oxidation activity are one and the same. The monolayer catalysts are the best partial oxidation catalysts. 

Solid-state NMR Correlated ab initio and density-functional calculations... 

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