DOSY NMR

DOSY NMR can also be used to study organic contaminants. Thus far only a few applications have been published, the best examples being Dixon et al. (1999), Simpson et al. (2002a), and Otto et al. (2003). Dixon et al. looked at the interactions between fluoro-acetonaphthone and the Suwannee River fulvic acid, Simpson et al. looked at competitive binding between a herbicide and MTBE (a petroleum additive) with NOM, and Otto et al. investigated the interactions between humic substances and surfactants. 

DOSY NMR 2-dimensional diffusion ordered spectroscopy nuclear magnetic resonance (spectroscopy) dpb bis(dibenzylideneacetone) dppe 1,2-bis(diphenylphosphino)ethane DSC differential scanning calorimetry DV differential viscometry... 

Therefore, we connected the tri-urea 27 with three tetra-ureas 28, via covalent linkers, to a building block A. In apolar solvents molecules A alone would form crosslinked polymers via dimeric substructures formed by the tri- and tetra-ureas. Together with the building block B, a tetra-tosylurea substituted by four phthalimido alkylether residues, this polyassociation is prevented by the formation of heterodimers between tetra-aryl- and tetra-tosylureas. A solution of A and B in the ratio 2 6 therefore contains exclusively the dendritic assembly shown in Figure 5.21, as proved by light scattering and DOSY NMR spectroscopy [69]. 

In this study, another asset of the DOSY NMR technique was to discriminate, within mixtures, the components displaying different diffusion coefficients [54]. For example, when studying dynablock 7A in water, the correlation between the resonance signals in the first dimension with the diffusion values in the second dimension led to the following conclusions. The imine dynablock diffuses with a rate of 28 pm2 s-1, corresponding to a micellar object of 14.2 nm in diameter which contains in its core all the remaining free aldehyde while the free amine stays outside of the micellar system with a diffusion of 250 pm2 s-1. This location of the free aldehyde within the boundary of the structure is the first requirement to access an autopoietic behavior. 

Giuseppone N, Schmitt J-L, Allouche L, Lehn J-M (2008) DOSY NMR experiments as a tool for the analysis of constitutional and motional dynamic processes implementation for the driven evolution of dynamic combinatorial libraries of helical strands. Angew Chem Int Ed 47 2235-2239... 

Analysis of the genuine formulation of Cialis using conventional and 2D DOSY NMR... 

There has also been a recent assessment of different methods for the processing of diffusion ordered spectroscopy (DOSY) NMR experiments. This included the evaluation of iterative single channel methods including single channel methods such as... 

Examples of the application of MCR to both 2D DOSY NMR data23 and 3D [jH-15N] HSQC NMR data24 can be found. In the latter case, the reaction between 15N-labelled cisplatin and the amino acid-nucleotide hybrid (Phac-met-linker p5 dG) is monitored and both analysis of the individual 2D HSQC spectra as well as the simultaneous analysis of all 2D HSQC spectra over time is performed in which case the kinetic reaction profiles can be obtained. The authors found that sub-structures involved in local unfolding as a consequence of the addition of denaturant could be identified, and that this would hardly have been possible without multivariate analysis of the data. 

PNMR = Pulse gradient-field spin echo (PGSE) NMR, DNMR = diffusion ordered spectroscopy (DOSY) NMR, Elec = Electrochemistry, ENMR = fringe field NMR. 

Figure 14 Synthesis of tritopic terpyridine ligands 52—54 using the Sonogashira coupling and their self-assembly into cage structures 55—57 under thermodynamic control with IVl = Zn". Energy minimized structures and dimensions and 2D DOSY NMR spectra of 55 (left), 56 (middle), and 57 (right). Adapted with permission from Ref. 14JA10499. Copyright 2014 American Chemical Society.

Diffusion ordered projection spectroscopy (DOPY) H/ H DOSY NMR Resolution improvement of correlated signals [123]... 

Further information is provided by diffusion-ordered spectroscopy (DOSY)-NMR. With DOSY-NMR the diffusion coefficient, Dexp, can be measured. The measured diffusion coefficients, however, are not the diffusion coefficients of the free ions. They represent some average of the fully dissociated and paired states. Nevertheless, knowledge of the measured (NMR) diffusion coefficients together with the degree of ion dissociation allows calculation of the diffusion coefficients of the free ions [21]. 

Another approach to improve the tractability of the spectra is to introduce additional dimensions complementary to the chemical shifL Two such approaches have been explored Lehn et al. have used DOSY NMR, where the differences in diffusion times of the library members are used as the second dimension [7], and Jeannerat and Prins et al. have used H- C-HSQC NMR and also introduced a temporal dimension, by adding different building blocks at different times and monitoring the evolution of the two-dimensional (2-D) NMR spectrum [6]. 

Scheme 2.3 Building blocks used to generate a small DCL of linear hydrazides that can adopt helical conformations and that was analyzed by DOSY NMR to reveal five different compounds (n = 0-4) [7],...

DOSY NMR and DLS analysis were performed to determine the hydrodynamic diameters of dendrimers 1 and 2. Interestingly, very large values of DLS were obtained, which indicates the aggregation of a number of dendrimers and the formation of supramolecular assemblies of dendrimers. This observation was attributed to interdendritical interactions of TEG-termini. 

More advanced techniques have been used effectively. Fogg has applied DOSY (diffusion-ordered spectroscopy)to separate the NMR signals for cyclic product and cyclic dimer in model RCM reactions such as that illustrated in Scheme 2.55. DOSY NMR resolves signals based on their diffusion coefficient one dimension of the resulting 2D spectra is the NMR spectrum, while the other is the diffusion coefficient (a time-bound parameter), which is related to molecular weight. Later, Sliwa showed that the same technique could be applied to discriminate between... 

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