Solid-state heteronuclear correlation experiment

In order to confirm this view, we performed the solid-state heteronuclear correlation experiment, which can measure spin diffusion more accurately. With... 

Recently two-dimensional solid-state heteronuclear chemical shift correlation experiments involving magic angle sample spinning (MASS) have been described. This technique results in an increase in the resolution of solid-state proton spectra by a factor of 5-10. Solid-state NMR spectroscopy has hitherto been confined to C-NMR spectra since the residual line widths in the spectra of solid samples are around 2 ppm, so that only four or five nonequivalent protons can be distinguished in the normal proton spectral region of 10-15 ppm. The increase in resolution attained by the 2D solid-state heteronuclear COSY experiment should promote further studies of the H-NMR spectra of solid samples. 

Judeinstein et al have conducted direct measurement of through-space NMR interactions that provide definitive evidence for spatial proximity of different species. Dipole-dipole interactions can be measured in principle between any NMR active nuclei with heteronuclear correlation experiments in the liquid or solid state." The dipole-dipole interactions decay quickly with the internuclear distances (r ), and are difficult to evaluate for long-range distances and even more difficult when exchange, conformation, or motion phenomena are present. However, the measurement of the nuclear Overhauser method" based on the dipole-dipole-induced crossrelaxation, was proposed to successfully measure intermolecular interactions" and the formation of ion pairs." " In agreement with recent studies, the pulsed field gradient enhanced inverse HOESY (heteronuclear Overhauser enhancement spectroscopy) sequence is usually preferred because it is more sensitive for isotope pairs H- Li and also improves the digital resolution in the H crowded spectrum." ... 

In this section 10.2, we review the various solid-state NMR methods used to investigate interpolymer interactions, molecular motion and the spatial structure of a polymer blend. An interaction between component polymers affects the chemical shifts and lineshapes (see Section 10.2.2.1) and the molecular motions of the component polymers (see Section 10.2.2.2). In Section 10.2.3.1, microheterogeneity from 2 to 50 nm is studied by measuring spin diffusion indirectly from its effects on H spin-lattice relaxation. The spin-diffusion processes can also be monitored by several methods based on the Goldman-Shen experiment [8] (see Section 10.2.3.2). Homonuclear and heteronuclear two-dimensional correlation experiments reveal how and to what extent component polymers interact with each other (see Section... 

We present a solid-state nuclear magnetic resonance (NMR) experiment that allows the observation of a high-resolution two-dimensional heteronuclear correlation (2D HETCOR) spectrum between aluminum and phosphorous in aluminophosphate molecular sieve VPI-5. The experiment uses multiple quantum magic angle spinning (MQMAS) spectroscopy to remove the second order quadrupolar broadening in Al nuclei. The magnetization is then transferred to spin-1/2 nuclei of P via cross polarization (CP) to produce for the first time isotropic resolution in both dimensions. 

An interesting three-dimensional separated-local-field/dilute-spin-exchange solid state NMR experiment has been reported where homonuclear spin-exchange cross-peaks provide correlation in the un u>z plane. Resonances are resolved along the u> axis by their heteronuclear dipolar couplings. The experiment was demonstrated experimentally with the heteronuclear and N- N homonuclear dipole-dipole interactions in... 

Small scalar /-couplings between quadrupolar nuclei and spin-1/2 have been measured in inorganic solids using /-Resolved experiments. These were further used to acquire 2D /-HMQC heteronuclear correlation spectra, giving detailed insight into the chemical bonding scheme in the solid state. ... 

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