Solid-state nuclear magnetic resonance spectra

Solid-state nuclear magnetic resonance spectra of Phosphoria shales (37) indicate the residence of higher amounts of aliphatic carbon in the thermally immature samples from southwestern Montana compared to thermally mature samples from Idaho. Similarly, gas chromatographic analyses and the ratio of hydrocarbon to carbon (4 ) indicate thermal immaturity and the potential for hydrocarbon generation in the southwestern Montana oil shales in contrast to the depleted hydrocarbon-producing potential of kerogenic shales in other areas. 

Completely decoupled solution-phase and (2) solid-state nuclear magnetic resonance spectra obtained for benoxaprofen. The solution phase spectrum is compared with the sohd-state spectram of Form I. (The figure was adapted from data contained in Ref. 152.)... 

F. H. Larsen, Simulation of Molecular Motion of Quadrupolar Nuclei in the Solid-State Nuclear Magnetic Resonance Spectra , in Annual Reports on NMR Spectroscopy, ed. G. A. Webb, Elsevier, 2010, Vol. 71, p. 103. 

C. Filip, S. Hafiier, I. SchneU, D.E. Demco, H.W. Spiess, Solid-state nuclear magnetic resonance spectra of dipolar-coupled multi-spin systems under fast magjc angle spinning, J. Chem. Phys. 110 (1999) 423. 

H.G. Brittain, unpublished results for solid-state nuclear magnetic resonance spectra obtained at a frequency of 270 MHz, using a combination of magic-angle spinning and cross-polarization. The spectra were obtained using a contact time of 1 millisecond and a 3 second recycle time. 

Raman Spectrum C Solid-State Nuclear Magnetic Resonance Spectrometry... 

In terms of the structural features that are probed with various analytical methods, solid state nuclear magnetic resonance (SSNMR) may be looked upon as representing a middle ground between IR spectroscopy and X-ray powder diffraction methods. The former provides a measure of essentially molecular parameters, mainly the strengths of bonds as represented by characteristic frequencies, while the latter reflect the periodic nature of the structure of the solid. For polymorphs differences in molecular environment and/or molecular conformation may be reflected in changes in the IR spectrum. The differences in crystal structure that define a polymorphic system are clearly reflected in changes in the X-ray powder diffraction. Details on changes in molecular conformation or in molecular environment can only be determined from full crystal structure analyses as discussed in Section 4.4. 

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. 

Figure 9 (A) Typical line shape of an observed quadrupolar nucleus S, showing the second-order quadrupole shift AcTqs, and the relative position of the centre-of-gravity with respect to the isotropic chemical shift ajso- (B) Al solid-state MAS NMR spectrum of Sr8(AI02)i2-Se2 at 78.15 MHz (7.05 T). Asterisks denote sidebands. Reproduced with permission of Elsevier Science Publishers from Weller MT, Brenchley ME, Apperley DC and Davies NA (1994) Correlations between aI magic-angle spinning nuclear magnetic resonance spectra and the coordination geometry of framework alumlnates. Solid State Nuclear Magnetic Resonance Z 103-106.

Fig. 5. Solid-state i C nuclear magnetic resonance spectrum of corn cob xylan.

Physicists have long been aware of the power and usefulness of high-resolution solid-state NMR. Even prior to the development of cross-polarization, in the early to mid-seventies, it was clear that, by recording the nuclear magnetic resonance spectrum when the sample was spun at the magic angle (5 M1) to the magnetic field, chemical shifts could be readily identified... 

Co-crystal patents usually contain experimental examples that describe the preparation of the co-crystal and the characterization of the co-crystal. Characterization of the co-crystal describes the co-crystal itself and its various properties which include its sohd state characteristics and stoichiometry. Typically, the sohd state characteristics of a crystalline solid are shown by one or more of the foUowing analytical techniques X-ray powder diffraction pCRPD), single crystal X-ray diffraction (SCXD), Raman spectroscopy, infrared (IR) spectroscopy, sohd state nuclear magnetic resonance spectroscopy (SSNMR), and differential scanning calorimetry (DSC). The stoichiometry of a co-crystal may be estabhshed through solution techniques such as comparison of peak integrations in a solution NMR spectrum, data... 

Solid state materials have been studied by nuclear magnetic resonance methods over 30 years. In 1953 Wilson and Pake ) carried out a line shape analysis of a partially crystalline polymer. They noted a spectrum consisting of superimposed broad and narrow lines which they ascribed to rigid crystalline and amorphous material respectively. More recently several books and large articles have reviewed the tremendous developments in this field, particularly including those of McBrierty and Douglas 2) and the Faraday Symposium (1978)3) —on which this introduction is largely based. 

Solid-state C variable-amplitude cross polarization magic-angle spinning (VACP/MAS) nuclear magnetic resonance (NMR) spectra were acquired for the sorbitol samples. Proton decoupling was achieved by a two-pulse phase modulation (TPPM) sequence. Identical C spectra were measured for the y-form sorbitol samples, and a representative spectrum is shown in Figure 9. 

Figure 15.9. 13C CPMAS NMR spectrum of humin extracted from a brown chernozem soil from Western Canada. The characteristic doublet in the unsubstituted aliphatic region is characteristic of methylene carbon (28-34 ppm) and shows the presence of both amorphous (soft) domains at 29 ppm and crystalline (rigid) domains at 33 ppm in soil humin. Reprinted from Simpson, M. I, and Johnson, R C. E. (2006). Identification of mobile aliphatic sorptive domains in soil humin by solid-state 13C nuclear magnetic resonance. Environ. Toxi. Chem. 25, 52-57, with permission from the Society of Environmental Toxicology and Chemistry.

Another technique which is widely used for functional group analysis of humic materials is carbon-13 nuclear magnetic resonance specroscopy ( C-NMR). The C-NMR solid-state spectrum of an aquatic humic acid is shown in Figure 5. The band assignments for the types of carbon that can be detected by NMR are listed in Table III. Again, bands are broadened due to the presence of free radicals in the structure. More information can be obtained with C-NMR regarding the carbon skeleton of the humic... 

An illustration in PR shows, as a small icon of spectroscopic progress, the improvement in sensitivity of nuclear magnetic resonance spectrometry. In only 15 years, the solid-state 13C spectrum of adaman-tane, with only two types of carbons, CH and CH2, had turned from inaccessibility to an easy routine. Such solid-state 13C spectra became important diagnostic tools for the chemical industry in the areas of polymers, whether as elastomers, textile fibers, or plastics such as polypropylene. 

---