Solid-state nuclear magnetic resonance Raman spectroscopy

Analytical techniques commonly used to check for solid-state characteristics include melting point (including hot-stage microscopy), solid-state infrared spectroscopy, x-ray powder diffraction, thermal analysis (e.g., differential scanning calorimetry, thermogravimetric analysis, and differential thermal analysis), Raman spectroscopy, scanning electron microscopy, and solid-state nuclear magnetic resonance (NMR). 

The characterization of the physical properties of pharmaceutical compounds under development is often conducted using a variety of techniques including DSC, TGA, XRD, HSM, solid-state nuclear magnetic resonance (NMR), infrared (IR) and Raman spectroscopy, moisture uptake, particle size analysis, scanning electron microscopy (SEM), and micromeritic assays. A typical initial analysis of a pharmaceutical compound under development in a materials characterization group would include DSC, TGA, HSM, and XRD analyses. These four techniques are chosen because the data generated from them, when viewed collectively, comprise a relatively complete initial analysis of the physical properties of the compound. The DSC, TGA, and HSM assays... 

The enantiomer and the racemic compound possess different crystal structures, which correspond to different intermolecular interactions, as mentioned in Sec. 3. Therefore the enantiomer and the racemic compound exhibit different powder x-ray diffraction (PXRD) patterns, different infrared (IR) and Raman spectra, and different solid-state nuclear magnetic resonance (SSNMR) spectra. However, the opposite enantiomers give identical PXRD patterns, and identical IR, Raman, and SSNMR spectra. Consequently, the PXRD patterns and the above spectra of a conglomerate, which is a physical mixture of opposite enantiomers, are identical to that of the pure enantiomers. In contrast, the diffraction pattern and the various corresponding spectra of the racemic compound usually differ significantly from those of the pure enantiomers. Therefore the type of racemate can be easily determined by comparing the diffraction patterns or the various spectra of the racemic species with that of one of the pure enantiomers (Figs. 3 5). The enantiomeric composition in a racemic mixture may be determined by PXRD, or by IR or SSNMR spectroscopy. Quantitative PXRD has been applied to determine the relative... 

More recently, a number of new structure sensitive techniques have been developed, and they have been applied to studies of cellulose. These include Raman spectroscopy and Solid State Nuclear Magnetic Resonance, in the experimental arena, and conformational energy calculations in the theoretical domain. These are more recent contributions and are the subjects of subsequent sections in this chapter and later chapters in these proceedings. 

Several surface-sensitive techniques can provide details about bonding in amorphous materials. Such information complements structural analyses obtained by traditional bulk analytical techniques like Raman and infrared spectroscopy, solid state nuclear magnetic resonance spectroscopy, and Mossbauer spectroscopy. 

From the many available spectroscopic techniques, the most frequently employed to provide information at the microscopic level in the study of zeolites are. X-ray diffraction and Inelastic Neutron Scattering (INS), infrared (IR) or Raman absorption spectroscopy and mmltinuclear Solid State Nuclear Magnetic Resonance (NMR). 

Raman spectroscopy with variable temperature accessories has been valuable for probing phase transitions within solid-state pharmaceutical samples. In combination with other techniques [x-ray diffractometry, solid-state nuclear magnetic resonance (NMR), FTIR spectroscopy, and thermal analysis], the molecular basis for thermal transitions between dihydrates of carbamazepine prepared from different polymorphs of the drug were re-... 

Fourier transform infrared spectroscopy was applied to the study of lac resin, a complex natural resin of insect origin, and some of its derivatives. The results obtained by this method are compared with those from earlier studies that used classical methods of chemical analysis. Experiments include the preparation of hard and soft resins, dewaxed lac, ammoniated lac, lac acetal, halogenated lac, hydrolysed lac, rebuilt lac (rebulac), and the preparation of lac metal salts. It is found that FTIR has several advantages over classical methods, but that FTIR data requires supplementing by other instrumental techniques such as FT-Raman spectroscopy and solid state nuclear magnetic resonance. 21 refs. 

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... 

In this chapter, three methods for measuring the frequencies of the vibrations of chemical bonds between atoms in solids are discussed. Two of them, Fourier Transform Infrared Spectroscopy, FTIR, and Raman Spectroscopy, use infrared (IR) radiation as the probe. The third, High-Resolution Electron Enetgy-Loss Spectroscopy, HREELS, uses electron impact. The fourth technique. Nuclear Magnetic Resonance, NMR, is physically unrelated to the other three, involving transitions between different spin states of the atomic nucleus instead of bond vibrational states, but is included here because it provides somewhat similar information on the local bonding arrangement around an atom. 

Spectroscopic methods, such as FT-infrared (FTIR) and Raman spectroscopy detect changes in molecular vibrational characteristics in noncrystalline solid and supercooled liquid states. Various nuclear magnetic resonance (NMR) techniques and electron spin resonance (ESR) spectroscopy, however, are more commonly used, detecting transition-related changes in molecular rotation and diffusion (Champion et al. 2000). These methods have been used for studies of the amorphous state of a number of sugars in dehydrated and freeze-concentrated systems (Roudaut et al. 2004). 

The identification of isomers is as important as their synthesis and purification. The technique to be used for this purpose depends on the species to be analyzed and if it is in solution or in solid state. Without doubt if there are crystals of the material to be analyzed the best way to do it is by X-ray diffraction, but there are other techniques that can be used, such as infrared and Raman spectroscopy, electronic paramagnetic spectroscopy, nuclear magnetic resonance, and electronic spectroscopy. The choice of which technique to use depends on the intrinsic property of the material to be analyzed, and whether it presents paramagnetic or magnetic properties. 

Framework and Surfaces Since compositions and structures are very diverse, surface and framework properties are also extremely varied. In terms of compositions, coordination, and chemical environments, several methods are particularly informative for the characterization of nanoporous solids, such as nuclear magnetic resonance methods (NMR), UV-visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, x-ray absorption spectroscopies, x-ray photoelectron emission spectroscopy (XPS), and electron paramagnetic resonance (EPR) (4, 6). Among them, sohd state NMR techniques arc largely employed and will be briefly described in the following. 

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