Diffusion-ordered NMR spectroscopy

Morris, K. F., Cutak, B. J., Dixon, A. M., and Larive, C. K. (1999). Analysis of diffusion coefficient distributions in humic and fulvic acids by means of diffusion ordered NMR spectroscopy. Anal. Chem. 71, 5315-5321. 

Structural studies on the mechanism of the THF-catalyzed vinylic lithiation of allylamine derivatives have been performed using 2D and diffusion-ordered NMR spectroscopy.10 NMR evidence has suggested that in THF the mixed aggregate has close contact between the alkene and the /S-CfG of n-BuLi, whereas in the absence of THF, the allyl chain appears to be pointed away from the nearest n-BuLi residues. 

Detection of n-n interactions has largely relied on NMR-based techniques, such as chemical shifts variations,and Nuclear Overhauser Effect Spectroscopy (NOESY) or Rotating-Erame NOE Spectroscopy (ROESY)7 Diffusion-ordered NMR spectroscopy (DOSY) has also been used to detect n-n stacked complexes. ... 

This can convieniently be achieved by applying diffusion-ordered NMR spectroscopy (DOSY) [23, 24],... 

Various new techniques suitable for estimating D are now available fluorescence correlation spectroscopy (FCS) [5], fluorescence recovery after photobleaching (FRAP) [6], pulsed field gradient nuclear magnetic resonance (PFG-NMR) [7], diffusion ordered NMR spectroscopy (DOSY) [8], and others. Among these, FCS and FRAP are popular in biological studies because they are often installed on a commercial LSM system and conveniently coupled with it. 

Diffusion—ordered NMR spectroscopy is another NMR method which is used to analyze binding properties. This method is discussed later in this book. 

Clearly, a choice had to be made as to which of the many methods available today should be included. This choice is likely biased to some extent by the editor s own preferences and a reader might arrive at the conclusion that another choice would have been better. Some chapters deal with methods of fundamental importance. For example, Chapter 2 provides a practical guide to the determination of binding constants by NMR and UV methods and thus covers an aspect imminently important to the field, which deals with noncovalent binding and weak interactions. Similar arguments hold for the next two chapters on isothermal titration calorimetry and extraction methods. The following chapters on mass spectrometry, diffusion-ordered NMR spectroscopy, photochemistry, and circular dichroism do... 

There are further classes of experiment that result in pseudo-2D NMR spectra. These do not have a second frequency axis resulting from Fourier transformation of a variable time, but the second axis is some other parameter. One example is provided by continuous-flow directly coupled HPLC-NMR spectra where the second axis in the pseudo-2D plot is the chromatographic retention time. Another example is diffusion-ordered NMR spectroscopy where the second axis plots the molecular diffusion coefficient associated with each NMR peak, this parameter being derived from the dependence of peak intensities on the square of an applied magnetic field gradient. 

W. J. Lough, Alternative Analytical Techniques for Determination or Isolation of Drug Enantiomers , in Drugs and the Pharmaceutical Sciences, eds. K. Jozwiak, W. J. Lough and I. W. Warner, Informa Healthcare, 2012, Vol. 211, Drug Stereochemistry, Analytical Methods and Pharmacology, p. 167. A. Macchioni, G. Ciancaleoni, C. Zuccacda and D. Zuccaccia, Diffusion Ordered NMR Spectroscopy (DOSY) , in Supramolecular Chemistry From Molecules to Nanomaterials, eds. P. A. Gale and J. W. Steed, John Wiley Sons Ltd., Chichester, UK, 2012, Vol. 2, p. 319. 

Voltammetric and other electrochemical techniques can be used to determine D values of redox-active species. For instance, in CV experiments the slope of a plot of peak current versus scan rate depends on (D) / according to (9). However, in the last few years the popularity of NMR methods to determine D values has increased almost exponentially. NMR spectroscopy offers some advantages for this purpose, as the determination relies on the rate of signal intensity decay as a function of applied field gradient and does not require previous knowledge of the concentration of the diffusing species (see Diffusion Ordered NMR Spectroscopy (DOSY), Techniques). Unlike with electrochemical methods, the diffusing species do not have to be... 

D. Li, I. Keresztes, R. Hopson and P. G. Wdliard, Characterization of Reactive Intermediates by Multinuclear Diffusion-Ordered NMR Spectroscopy (DOSY) , Acc. Chem. Res., 2009, 42, 270. 

Diffusion-ordered NMR spectroscopy (DOSY) is a powerful tool for structural studies of molecular aggregates in solution. Translational diffusion coefficients (D) determined by DOSY correlate directly with the sizes and dimensions of aggregates. The diffusion coefficients of 18 and a 1 1 mixture of 18 and 19 at a low concentration in chloroform-(ij are 4.09 x 10and 2.57 x 10 ° m S", respectively. The ratio of D1S.19/D19 of 0.63 was reasonably close to the theoretical range of 0.59 to 0.60 expected for a linear trimer. These results confirmed the formation of oligomeric assemblies even at low concentrations. 

M. Urbanczyk, W. Kozminski, K. Kazimierczuk, Accelerating diffusion-ordered NMR spectroscopy by j oint sparse sampling of diffusion and time dimensions, Angew. Chem. Int. Ed. 53 (2014) 6464-6467. 

Figure 26 8 Cyclic poly(oxyethylene) (as 30-crown-10) can be threaded and trapped onto linear polystyrene by polyrotaxanation. Diffusion-ordered NMR spectra of (a) poly[(styrene)-/o/flia-(30-crown-10)] (PS-roroxfl-30cl0, structure shown at top), and (b) blend of 30-crown-lO with PS-zo/oia-30c 10 (4/96, w/w) The polystyrene sports bulky ferf-butyl-containing end groups (labeled in spectra as t-Bu). The 30-crown-10 (3.7 ppm) in the polyrotaxane exhibits the same diffusion coefficient as the polystyrene (dashed horizontal line), which means it must be threaded. This is confirmed when some 30-crown-10 is added to the polyrotaxane and exhibits a separate, larger diffusion coefficient at the same chemical shift. (Reprinted with permission from T. Zhao and H.W. Beckham, Quantitative determination of threading in rotaxanated polymers by diffusion-ordered NMR spectroscopy, Macromolecules, 36, 4833 837, 2003. 2003 American Chemical Society.)...

Zhao, T., Beckham, H.W., and Gibson, H.W. (2003) Quantitative determination of threading in rotaxanated polymers by diffusion-ordered NMR spectroscopy. Macromolecules, 36,4833-4837. 

In addition to supramolecular polymers constructed from 9, bifunctional monomer 10 (Scheme 10.3), incorporating a less-flexible trimethylhexyl linker, exists in an equilibrium between cyclic and linear aggregates in solution as evidenced by viscosity studies and diffusion-ordered NMR spectroscopy (DOSY). These results are in line with the proposal of equilibrium between linear polymeric and oligomeric cyclic structures (i.e., ring-chain equilibrium). Because of its restricted conformational freedom, 10 is more prone to the formation of rings than 9. 

The active base is accessed simply through mixing Li(TMP) with the appropriate metal salt MCI2 in a 3 1 stoichiometric ratio in THF solution. However, 2-dimensional DOSY NMR studies (diffusion-ordered NMR spectroscopy, Fig. 22) suggested that the black box THF solution mixtures are actually more complicated in practice, hinting that ate formation had not taken place to any... 

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