Proton spin-lattice relaxation time rotating frame

Recently, Lipton et al. [25] have used zinc-67 NMR to investigate [Zn(HB(3,5-(CH3)2pz)3)2] complexes which have been doped with traces of paramagnetic [Fe(HB(3,4,5-(CH3)3pz)3)2]. The low-temperature Boltzmann enhanced cross polarization between XH and 67Zn has shown that the paramagnetic iron(II) dopant reduces the proton spin-lattice relaxation time, Tj, of the zinc complexes without changing the proton spin-lattice relaxation time in the Tip rotating time frame. This approach and the resulting structural information has proven very useful in the study of various four-coordinate and six-coordinate zinc(II) poly(pyrazolyl)borate complexes that are useful as enzymatic models. 

The precipitates of PVPh/PDMA from methanol and acetone solutions were examined by CPMAS NMR [51], and evidence for specific interaction was obtained with a 3 ppm shift in the phenolic carbon resonance peak. The proton spin-lattice relaxation times Tj were shorter than those predicted by a linear model, though the rotating frame spin-lattice relaxation times Tjp of the com-... 

As an NMR methodology for elucidating miscibility in the PLA/PLV, PLA/PLIL, PDA/PLV and PG/PLV blends, the proton spin-lattice relaxation times in the rotating frame ) for homopolypeptides and their... 

Carbon spin-spin relaxation times, T2C, under CP-MAS conditions can provide motional information about the individual carbon site of interest, in contrast to the case of proton spin-lattice relaxation times in the rotating frame, TlpH, in which information on individual sites would be masked by the presence of a rapid spin-spin process. In general, the T2C values strongly depend on the... 

The build-up of signal during cross-polarization depends on two relaxation processes (Fig. 7), the cross-polarization transfer time, CH and the proton spin-lattice relaxation time in the rotating frame, Ti . Figure 7 shows that the signal intensity builds exponentially at a rate characteristic of CH> while at the same time the signal is being truncated by another exponential... 

Hartmann and Hahn [39] showed that CP can be achieved when two rf fields Bin and B c = 4Bih are simultaneously applied. Jn/jc = 4, so, when B c = 4Bm energy is transferred between them, or they are cross-polarized, because Tc ic = Th ih (which is called the Hartmann-Hahn match of heteronuclear rotating-frame frequencies). In the CP experiment C nuclei obtain their spin polarization from H nuclei, so, not only do the shorter proton spin-lattice relaxation times determine the repetition rate of... 

Table 24.1 Proton spin-lattice relaxation time in the rotating frame values for all resolved of SBR, SBR/T102 nanocomposite, SBR/T102 photodegraded nanocomposite.Copyright 2009. Reproduced with permission from Elsevier Ltd.

A quantitative analysis of the mixing scale in the PACMO/CA (DS = 2.18) blends was carried out through measurements of proton spin-lattice relaxation times in the rotating frame (T ). values can be obtained by practically fitting the decaying carbon resonance intensity to the following single-exponential function ... 

TipH Proton spin-lattice relaxation time in the rotating frame... 

The combining NMR techniques in the solid state permit the evaluation of the polymeric systems homogeneity. In polycarbonate-polyvinyl pyrrolidone blends, the response of proton spin-lattice relaxation time in the rotating frame was the determinant to obtain information on the transition when the quantity of polyvinyl pyrrolidone is close to 40 wt% and a better organisation of amorphous phase was detected. 13 refs. 

Fig. 28. Proton spin-lattice relaxation times in the laboratory system (Tj) and in the rotating frame (Tip) of polyisobutylene (PIB) melts as a function of the frequency (v, Lar-mor frequency in the laboratory frame Vi=yBi/(27i), rotating-frame nutation frequency) [125]. The data refer to the molecular weight independent chain-mode regimes I (high-mode-number limit) and II (low-mode-number limit) [49], The arrow indicates the crossover frequency between regions I and II...

Different solid-state NMR techniques CPMAS NMR, the second moment of the signal, the spin-lattice relaxation time in the rotating frame T p) were combined to reach the conclusion that in the case of por-phine H2P the double-proton transfer is followed by a 90° rotation within the crystal (see Scheme 2). 

Figure 1 Schematic representation of the 13C (or 15N) spin-lattice relaxation times (7"i), spin-spin relaxation (T2), and H spin-lattice relaxation time in the rotating frame (Tlp) for the liquid-like and solid-like domains, as a function of the correlation times of local motions. 13C (or 15N) NMR signals from the solid-like domains undergoing incoherent fluctuation motions with the correlation times of 10 4-10 5 s (indicated by the grey colour) could be lost due to failure of attempted peak-narrowing due to interference of frequency with proton decoupling or magic angle spinning.

Jonas et al. measured the proton rotating frame spin-lattice relaxation time (Tip) at pressures from 1 bar to 5000 bar and at temperatures of 50 to 70 °C for DPPC and at 5 to 35 °C for POPC. If intermolecular dipolar interactions modulated by translational motion contribute significantly to the proton relaxation, the rotating frame spin-lattice relaxation rate (1/Tip) is a function of the square root of the spin-locking field angular frequency... 

Another way of using JH NMR to study the dynamics of phenyl protons in BPA-PC consists in selective deuteration of the methyl groups (BPA-d6-PC) [32]. Thus, the temperature dependence of the JH spin-lattice relaxation time, Ti, and spin-lattice relaxation time in the rotating frame, T p, has been determined, and is shown in Fig. 38. 

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