Double resonance, NMR

Figure 5.6 Steric view of sickle structure of D-Glu-8 (1) in helical fibers based upon measurements made using rotational echo double-resonance NMR experiments. The N-C3 torsion angle (>Iy) is —100°, while the C1-C4 torsion angle (>I 4) is —53°. Reprinted from Ref. 40 with permission of The Royal Society of Chemistry on behalf of PCCP Owner Societies. 

Gullion, T. and Schaefer, J. (1989) Rotabonal-echo double-resonance NMR. . Magn. Reson, 81,196-200. 

Gullion, T. (1995) Measurement of dipolar interacbons between spin-1 /2 and quadrupolar nuclei by rotabonal-echo, adiababc-passage, double-resonance NMR. Chem. Phys. Lett., 246, 325-330. 

Wooley KL, Klug CA, Tasaki K, Schaefer J. Shapes of dendrimers fi om rotational-echo double-resonance NMR. J Am Chem Soc 1997 119 53-58. 

Rotational-echo double resonance NMR Tetramethyl bisphenol A polycarbonate Tetrachlorophthalic dimethyl ester Wiliams, Landel, Ferry... 

REDOR rotational echo double resonance (NMR spectroscopy)... 

Potentially, extremely large SNR enhancements are obtainable with double resonance NMR spectrometers with H frequencies 1000 times greater than the 14N NQR frequencies in TNT are available. Of course, such equipment is completely unsuitable for... 

Double-resonance NMR techniques involve simultaneous irradiation of the sample with two oscillating magnetic fields (Bj and B2) of frequencies v, and v2. This allows us to determine the effect of irradiating one set of nuclei (at v2) while observing the NMR signal of another set of nuclei (at v,). 

Mixtures of transition metal (Mo or W) sulphides dispersed on y-alumina supports are used in hydrotreatment processes to remove sulphur, nitrogen, oxygen and metals from oil fractions. The addition of phosphorus to these catalysts enhances the solubility and stability of molybdate and improves the thermal stability of the alumina support. Solid state P double-resonance NMR experiments ( P- AI REDOR and TRAPDOR) have been used to investigate the interaction between the impregnating phosphorus and the support surface (van Eck etal. 1995). The results showed that most of the phosphorus is in close contact with the aluminium, and that the layer of AIPO4 formed on the surface is not completely amorphous, but is slightly more ordered. 

Paik, Y., Yang, C., Metaferia, B., el al. (2007) Rotational-echo double-resonance NMR distance measurements for the tubulin-bound paclitaxel conformation, J. Am. Chem. Soc., 129, 361-370. 

It proved to be possible to identify ordered Si-O-Al environments in molecular sieves by 27Al -29Si REAPDOR (i.e. rotational echo adiabatic passage double resonance) NMR techniques.350 NMR studies have been reported for the following silicoaluminophosphate molecular sieves SAPO-5 351 SAPO-11 and -31 352,353 H-SAPO-34 and -37 354 and SAPO-44.355... 

T. Gullion and J. Schaefer, Rotational-echo double-resonance NMR. J. Magn. Reson., 1989, 81, 196-200. 

Pb and Al - Pb double resonance NMR data have been reported for a series of lead-containing zeolites. It has been proposed that lead cations are strongly affected by the sorption of water, with the NMR spectra of the resulting material consistent with a chemical equilibrium between Pb " cations and PbOH" cations. Double resonance experiments on dehydrated samples have yielded Pb-Al distances consistent with reported X-ray structure. 

H/ Na double resonance NMR techniques have been employed to study the modification of surface hydroxyls on Y-AI2O3 by sodium ions. A H—> Na CP experiment has been used resolve three kinds of sodium cations that are closely associated with surface hydroxyl groups. H Na spin echo double resonance experiments reveal the surface modification in more detail. 

Template / AlSBA-15 interaction double resonance NMR study and consequences on structural properties... 

Mesoporous Al-incorporated SBA-15 have been obtained by direct synthesis. The surfactant -aluminosilicate interaction during synthesis was studied by double resonance NMR (HETCOR and TRAPDOR) and confronted with the structural properties of the materials obtained after calcination. It is concluded that the microporosity of SBA-15 originates in the partial hydrolysis of the TEOS precursor itself rather than incomplete PEO - silicate phase separation. 

Gullion T (1998) Introduction to rotational-echo, double-resonance NMR. Concepts Magn Reson 10 277-289... 

Gulion et al. [169]. The C- REAPDOR (rotational echo adiabatic passage double resonance) NMR measurement was carried out using one part of and four parts of singly labelled samples prepared as P P-sheet and P P-sheet structures. The final results are presented in Fig. 2.36. 

Heteronuclear dipolar-coupling-based double-resonance NMR techniques such as rotational-echo double-resonance [98], rotational-echo adiabatic passage double-resonance (REAPDOR) [99] and transfer of populations in double-resonance [100] are useful tools for the characterization of intermediate-range ordering phenomena involving two unhke spins in a wide variety of materials. These techniques utilize the distance-dependent heteronuclear dipole—dipole interaction to obtain information on intemuclear distance between the two spins involved under the MAS conditions. 

H.M. Kao, C.P. Grey, Characterization of the Lewis acid sites in zeohte HY with the probe molecule trimethylphosphine, and P/ A1 double resonance NMR, Chem. Phys. Lett. 259 (1996) 459-464. 

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