Jump motion deuteration

Fig. 16. The rope jumping motion of the N04 crown of the functionalized calix[4]arene 10 on the coordinated Ag(I) ion. The flip-flop movement results from the fact that the N04 ring has too small an aperture to encompass the metal ion. In a CH2CI2/CH3OH solution (4 1 v/v, deuterated solvents) the oscillating motion slows down with temperature and stops at -20 °C...

Selective inversion recovery experiments i.e. only select frequencies within the powder pattern are excited, have also been performed on 2H for the purposes of studying molecular motion. Initial experiments were performed on deuterated dimethylsulfone (DMS) to demonstrate the utility of the experiment.46 Selective inversion recovery curves were fitted to a suitable motional model, a two-site jump model in the case of DMS, to yield the motional rates as a function of temperature. A significant feature of this work is that the activation energy for the motion so obtained differs markedly from that obtained from earlier 13C chemical shift anisotropy lineshape studies. 

Incoherent quasielastic neutron scattering measured as a function of hydration for powders of deuterated phycocyanin has been used to probe water motions (Middendorf et al., 1984). The simplest model accounting for the data was jump diffusion of water molecules between localized-sorption sites and the development of clusters of surface water at higher hydration (half-coverage of the surface, 0.15 h). This model is consistent with the picture developed from sorption thermodynamics. 

Deuterium NMR of polyphosphazenes substituted by perdeutero or selectively deuterated ethyls was interpreted by threefold jumps among the three conformational minima [30]. Molecular mechanics models gave support to a concerted motion of the ethyls surrounding the main chain, which is thus embedded in a "soft cylindrical environment, fitting a hexagonal lattice. 

Variable-temperature NMR experiments provide information about the dynamic processes that occur in solids. It is well known that, for a semicrystalline polymer such as polyethylene (PE), a higher rate of cooling from the melt leads to lower crystallinity C CP/MAS NMR establishes that the cooling rate also affects the structure and motion of the amorphous domain [217]. Many of the dynamic properties of PE, such as jump rates and activation energy, can be explained in terms of chain diffusion between the phases, as detected by 2-D exchange C NMR [218]. Very slow motions in the crystalline a-form of deuterated poly(vinylidene fluoride) have also been detected by exchange NMR [219]. Double-quantum transitions can occur in materials in which spin pairs are only a few bonds apart this... 

Figure 6. Analysis of molecular motions of the columnar phase of a tetrabenzocyclophane derivative by 2D exchange NMR. Top molecular structure and schematic diagram of the motion. The first sofa con-former is converted by pseudorotation into a second sofa conformer, this first step being followed by a proper rotation of the molecule. Bottom left deuter-on 2D exchange spectrum of the phenyl-ring deuter-ated compound showing the ridge pattern characteristic of 90 jumps. Bottom right stacking of the molecules in a column. For details see [97].

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