Spin polarization transfer

The observed polarization is primarily associated with the former parahydrogen protons. However, other protons may also experience a drastic signal enhancement due to nuclear spin polarization transferred to these nuclei via the nuclear Overhauser effect (NOE) or similar processes, both in the final reaction products as well as in their precursor intermediates. 

Pines and coworkers70 showed the feasibility of spin polarization transfer by SPINOE from laser-polarized 129Xe to surface 13C nuclei on low surface area materials in high-resolution solid-state NMR experiments. This technique provides the basis for novel surface 13C NMR investigations, e.g. of surface coatings, supported catalysts and electrode materials. 

While the original CP experiments were designed for the proton-to-rare spin polarization transfer, cross-polarisation in the spin system which do not involve protons (i.e. 31P —> 27A1 or even 27A1 —> 31P) have also been described.22,23 These experiments have been widely applied for characterization of the structure of molecular sieves as well as the catalytic activity of their acidic sites.5,22... 

Electron Spin Polarization Transfer from Radicals of Photoinitiators to Stable Nitroxyl Polyradicals... 

Several methods of signal enhancement have been developed to help overcome the inherently low sensitivity of important nuclei such as and These experiments rely on the principle of spin polarization transfer where magnetization on the more sensitive nuclei, usually H, is transferred to the attached nuclei of interest through a specific sequence of pulses and delays. The signal enhancement achievable through... 

Spin polarization transfer via SPINOE requires effective adsorption of laser-polarized 2 Xe on the sample under study. Figure 63 shows the - Xe MAS NMR spectra of laser-polarized - Xe adsorbed on fullerenes at 150 K. The spectra exhibit narrow signals at ca 0 ppm due to gaseous xenon and broad signals centered at 100-120 ppm (50-80 ppm wide), characteristic of adsorbed xenon. The intensity of the latter signals is 4-5 times higher for C70 than for Ceo, because the specific surface of the C70 sample was approximately twice the specific surface of Ceo and the mass of the C70 sample was 2.5 times the... 

Given the above, it was of interest to establish the direction of rotation of the triptycene in 37b. Preparation of isotopically labeled rotamers of 37b should be possible, but would require extensive synthetic, rotamer-separation, and structure-determination efforts. Fortunately, the spin polarization transfer NMR technique [43] affords the same information at a small fraction of the effort. In short, if one has a system that is conformationally mobile, but that mobility is slow on the NMR time scale, then one can polarize the spin of a slowly conformationally mobile atom, wait an appropriate time, and assay where (if anywhere) that polarization has moved to. 

The spin polarization transfer results demonstrate unequivocally that rotation occurs equally in both directions. That is, 37b does not behave as a ratchet. (More subtle issues, such as how we distinguish between uni/bidirectional rotation and helicene racemization, and why it is not necessary to resolve racemic 37b are addressed in the full paper [39b].)... 

Fig. 17. Results of spin polarization transfer experiment at 160 °C (calibrated temperature). The resonances for Ha, Hb and Hc (see 46) appear at d 7.6, 7.1 and 6.9 ppm (not necessarily respectively). The spin of the proton resonating at d 7.6 was polarized, and transfer of that polarization was monitored over time...

For leading references to the spin polarization transfer method, see (a) Dahlquist FW, Longmur KJ, Du Vernet RB (1975) J Magn Reson 17 406 (b) Frim R, Zilber G,... 

S-spin zero-quantum line shape is sufficiently broadened to allow S-spin polarization transfer. The broadening of the zero-quantum line can also be caused by chemical exchange ( motionally-driven spin diffusion ) [15, 18]. In a different approach one decouples the protons and removes the chemical-... 

Ishikawa et detected the free-induction signals of xenon atoms polarized by spin-exchange optical pumping. The temperature dependence of dissolution and spin-polarization transfer of xenon atoms in ethanol is measured by simultaneous detection of both xenon and ethanol protons. 

Jockusch S, Zeika O, Jayaraj N, Ramamurthy V, Turro NJ (2010) Electron spin polarization transfer... 

Jockusch S, Zeika O, Jayaraj N, Ramamurthy V, Turro NJ (2010) Electron spin polarization transfer from a nitroxide incarcerated within a nanocapsule to a nitroxide in the bulk aqueous solution. J Phys Chem Lett 1 2628-2632... 

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