NMR diffusion

The Lewis acid Hg3( i-C6F4)3 also forms a pi-acid/pi-base interaction with TR(carb). In addition to the crystal structure demonstrating the ABBABB pattern observed in other stacked materials which retain the aurophilic Au-Au interactions between four of the six basic Au(I) atoms of the BB moieties, studies have shown that the oligomeric acid/base interection is retained in solution. Pulsed gradient diffusion NMR studies [70] suggesting the oligomeric sizes and coupling... 

L. M. Schwartz, R. L. Walswofhry 2001, (Tortuosity measurement and the effects of finite pulse widths on xenon gas diffusion NMR studies of porous media), Mag. Reson. Imag. 19, 345. 

For diffusion NMR, which is another approach to the separation of polymer and additive signals by application of field gradients, see Section 5.4.1.1. 

Asakura, T., Ashida, J., Yamane, T., Kameda, T., Nakazawa, Y., Ohgo, K., and Komatsu, K. (2001). A repeated beta-turn structure in poly(Ala-Gly) as a model for silk I of Bombyx mod silk fibroin studied with two-dimensional spin-diffusion NMR under off magic angle spinning and rotational echo double resonance. / Mol. Biol. 306, 291-305. 

First, second, and third generation dendrimers based on THPE (core) and bis-MPA (repeating unit) have been synthesized and characterized. SEC and NMR analyses verified that the dendrimers were monodisperse. Diffusion NMR was used to determine the dendrimers hydrodynamic radii in deuterated chloroform. First, second, and third generation dendrimers were found to be 7.8, 10.3, and 12.6 A, respectively. These were in agreement with sizes as determined from molecular models (Biichi). 

Diffusions NMR spectroscopy (e.g. PGSE = Pulsed Gradient Spin Echo STE = Stimulated Echo DOSY = Diffusion Ordered Spectroscopy) is a straightforward and accurate method for determination of the self-diffusion coefficient of a molecule. Its principal use in dendrimer chemistry is for size determination of dissolved dendrimers since the self-diffusion coefficient is directly correlated with the hydrodynamic radius of the molecule via the Stokes-Einstein equation [24]. Although one-dimensional and multidimensional diffusion NMR experiments can thus make an important contribution to structural characterisation of dendrimers, they have been used comparatively rarely until recently [25, 26]. 

Diffusion NMR experiments performed by Newkome et al. show that the diffusion coefficients - and hence the hydrodynamic radii - can yield information about the influence of external factors (e.g. pH values) on the size and shape of dissolved dendrimers [26]. Since the spatial structure of a dendrimer in solution... 

Cohen, Y., Avram, L., Evan-Salem, T., Frish, L., Diffusion NMR in supramolecular chemistry , in Analytical Methods in Supramolecular Chemistry, Schalley, C. A., ed. Wiley-VCH Weinheim, 2007, pp. 163-219. 

Contents 1. Introduction 160 2. Methods to Achieve High-Resolution NMR Spectra in the Presence of Delaying Media 161 2.1. MAS for magnetic susceptibility averaging 161 2.2. Chrom-NMR without MAS 162 3. Mobility PFG 162 3.1. Diffusion NMR and its representation 162 3.2. Diffusion in multiphasic environments 164 3.3. Specificity of diffusion PFG measurements in porous media 165 4. Examples of Chrom-NMR 166 4.1. Comparison with Liquid Chromatography (LC) 166 4.2. Non-chromatographic mobile phases 169 5. Conclusions 171 Acknowledgements 172 References 172... 

Figure 12.22 The room temperature 129Xe NMR spectrum of the iPP/EP blend investigated by Xe diffusion NMR...

Hoehn-Berlage M, Norris DG, Kohno K, Mies G, Leibfritz D, Hossmann KA. (1995) Evolution of regional changes in apparent diffusion coefficient during focal ischemia of rat brain the relationship of quantitative diffusion NMR imaging to reduction in cerebral blood flow and metabolic disturbances.) Cereb Blood Flow Metab 15 1002-1011 Hossmann K-A, Hoehn-Berlage M (1995) Diffusion and perfusion MR imaging of cerebral ischemia. Cerebrovasc Brain Metab Rev 7 187-217... 

Nicolay K, Braun KP, Graaf RA, Dijkhuizen RM, Kruiskamp MJ (2001) Diffusion NMR spectroscopy. NMR Biomed 14 94-111... 

Gounarides JS, Chen A, Shapiro MJ, Nuclear magnetic resonance chromatography applications of pulse gradient diffusion NMR to mixture analysis and ligand-receptor interactions, J. Chromatogr., B Biomed. Sci. Applic., 725 79-90, 1999. 

The product, which was readily soluble in organic solvents including acetone, tetrahydrofuran, and methylene chloride, was characterized by ES1-MS, H, and 13C NMR spectroscopy, diffusion NMR spectroscopy, SAXS measurements and elementary analysis. In the ESI-MS, multiply charged ions [51-n TFPB]n+ with n = 7—11 containing the intact coordination cage were observed exclusively... 

Cohen Y, Avram L, Frish L (2005) Diffusion NMR spectroscopy in supramolecular and combinatorial chemistry an old parameter-new insights. Angew Chem Int Ed 44 520... 

In Sections 2.2 and 2.3, it is described that the network structures of polymer gels, especially microscopic inhomogeneity, may be detected through the diffusion behaviour of probe molecules of different sizes, which can be obtained by using time-dependent diffusion NMR spectroscopy. In this section, it will be... 

Kaucher MS, Lam YF, Pieraccini S, Gotarelli G, Davis JT. Using diffusion NMR to characterize guanosine selfassociation insights into structure and mechanism. Chem. Eur. J. 2005 11 164-163... 

Buffy, J. J., Waring, A. J. and Hong, M. (2005) Determination of peptide oligomerization in lipid bilayers using F-19 spin diffusion NMR. Journal of the American Chemical Society, 127(12), 4477 1483. 

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