Structure Analysis of Solids

Structure Analysis of Solids 15.2.1. Diffraction by Crystal Lattices 

With a few exceptions, this article deals with the crystalline solid state other aggregations such as liquid crystals are not covered. 

Naturally occurring crystals differ from ideal crystals in two main aspects  

The crystals available in practice thus lie somewhere between amorphous and ideally crystalline. but nearer the ideal end of the scale ( ideal imperfect crystals ). A crystalline specimen may be a single crystal (smallest dimension ca. 0.05 - 0.5 mm) or a polycrystalline material with crystallite size ca. 0.04 mm. 

High-polymer plastics occupy an intermediate position. According to the two-phase model [56] the amorphous phase is present along with the crystalline phase. The unit cells in the crystalline portion may be oriented in some preferred direc- 

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Structural analysis of solids under extreme pressure and temperature conditions... 

Furthermore, it is often possible to extract from the structural analysis of solid solvates a significant information on solvation patterns and their relation to induced structural polymorphism. An interesting illustration has been provided by crystal structure determinations of solvated 2,4-dichloro-5-carboxy-benzsulfonimide (5)35). This compound contains a large number of polar functions and potential donors and acceptors of hydrogen bonds and appears to have only a few conformational degrees of freedom associated with soft modes of torsional isomerism. It co-crystallizes with a variety of solvents in different structural forms. The observed modes of crystallization and molecular conformation of the host compound were found to be primarily dependent on the nature of the solvent environment. Thus, from protic media such as water and wet acetic acid layered structures were formed which resemble intercalation type compounds. 

This strengthens the case for treating structure analysis as a particular field of analytical chemistry despite the fact that, from the philosophical point of view, structure analysis can be considered as distribution analysis (topochemical analysis) of species in atomic dimensions. Structure analysis of solids follows a similar scheme like that given above. The characteristics of molecules are then linked with those of crystals and elementary cells. 

One of the most powerful methods of direct structural analysis of solids is provided by HRTEM, whereby two or more Bragg reflections are used for imaging. Following Menter s first images of crystal lattice periodicity (26) and... 

In spite of the large success of XRD in routine structural analysis of solids, this technique does present some limitations when applied to catalysis [1,9]. First, it can only detect crystalline phases, and fails to provide useful information on the amorphous or highly dispersed solid phases so common in catalysts [22], Second, due to its low sensitivity, the concentration of the crystalline phase in the sample needs to be reasonably high in order to be detected. Third, XRD probes bulk phases,... 

The FEM, which was originally developed for structural analysis of solids, has been very successfully applied in the past decades to viscous fluid flow as well. In fact, with the exponentially growing computer power, it has become a practical and indispensable tool for solving complex viscous and viscoelastic flows in polymer processing (20) and it is the core of the quickly developing discipline of computational fluid mechanics (cf. Section 7.5). 

The molecular structure of homocyclic S7 is of special interest insofar as it is not possible to construct a puckered ring in which the bond lengths, bond angles, and especially the dihedral angles typical for even membered rings such as S, Sg, and S12 are preserved [70]. A first X-ray structural analysis of solid 7 was attempted by Kawada and Hellner in 1970 who only derived a two-dimensional projection of the molecule. However, it was evident that the molecule must have a chair conformation and that the various dihedral angles of the molecule must differ significantly. 

Shoji et al.57 have studied the relation between l5N chemical shift and structural parameters such as primary and secondary structures of various natural abundance homopolypeptides in the solid state. In order to test systematically the power of l5N CP/MAS NMR for the structural analysis of solid polypeptides, they have prepared various kinds of model homopolypeptides ... 

A structural analysis of solid methane and [ H4]methane has been attempted on the basis of an interpretation of extensive i.r. absorption measurements of CH4, CD4, and mixed isotopic crystals containing CH4, CD4, CHD3, and CHgD at low concentration in matrices of light and heavy methane in crystalline phases I and II. The spectra indicate that solid CH4 and CD4 have the same crystal structures in phase I as in phase II. In phase I, there is apparently considerable motion in phase II there exist two types of molecular sites some molecules undergo quantized rotation similar to that found in noble-gas matrices while others order with a local symmetry that is slightly distorted from to... 

M. Nakagawa, M. Senga and Y. Seino, Structural Analysis of Solid Elec-trol5des for Lithium Secondary Battery. Structural Analysis of Lithium Sullide/Diphosphorus Pentasullide-Based Glass and Glass Ceramics by Solid P-NMR Method , Idemitsu Giho, 2008, 51, 197. 

Pyridazine-3(2//)-thiones exist in the thione form (14), as is evident from an X-ray structure analysis of pyridazine-3(2//)-thione. 6-Mercaptopyridazine-3(2//)-thione is predominantly in the monothiolmonothione form (15) in aqueous solution and in the solid state, 6-hydroxypyridazine-3(2//)-thiones are in the hydroxythione form (16) and 6-aminopyridazine-3(2//)-thiones exist in the aminothione form (17) for further details see (73HC(28)755). Cinnoline-4(l//)-thiones and phthalazine-l(2//)-thione have been shown on the basis of UV data and ionization constants to exist in the thione forms. 

Atomic structure and Microstructural analysis of solid materials, providing high lateral resolution... 

Solid state NMR is a relatively recent spectroscopic technique that can be used to uniquely identify and quantitate crystalline phases in bulk materials and at surfaces and interfaces. While NMR resembles X-ray diffraction in this capacity, it has the additional advantage of being element-selective and inherently quantitative. Since the signal observed is a direct reflection of the local environment of the element under smdy, NMR can also provide structural insights on a molecularlevel. Thus, information about coordination numbers, local symmetry, and internuclear bond distances is readily available. This feature is particularly usefrd in the structural analysis of highly disordered, amorphous, and compositionally complex systems, where diffraction techniques and other spectroscopies (IR, Raman, EXAFS) often fail. 

Due to these virtues, solid state NMR is finding increasing use in the structural analysis of polymers, ceramics and glasses, composites, catalysts, and surfaces. 

The most common ions observed as a result of electron-stimulated desorption are atomic (e. g., H, 0, E ), but molecular ions such as OH", CO", H20, and 02" can also be found in significant quantities after adsorption of H2O, CO, CO2, etc. Substrate metallic ions have never been observed, which means that ESD is not applicable to surface compositional analysis of solid materials. The most important application of ESD in the angularly resolved form ESDIAD is in determining the structure and mode of adsorption of adsorbed species. This is because the ejection of positive ions in ESD is not isotropic. Instead the ions are desorbed along specific directions only, characterized by the orientation of the molecular bonds that are broken by electron excitation. 

The crystal structure analysis of the parent 1,2,3-triazole in the solid state unambiguously demonstrated that it crystallizes as a 1 1 molecular complex of both possible tautomers 24a and 24b, linked by a N-H - N hydrogen bond [97AX(C)1846]. 

Attempts to prepare related hpp complexes of tantalum were only partially successful. Reaction of 2 equivalents of either (hpplSiMes or in situ generated Li[hpp] with Tads afforded a solid that analyzed correctly for the compound (hpp)2TaCl3. X-ray structural analysis of the crystallized product identified the coordination isomer [Ta(hpp)4][TaCl6], with a distorted dodecahedral cation and a regular octahedral anion (Figure 28). °... 

Reaction of Ph2PLi with Pr N = C = NPr in THF proceeds via insertion of the carbodiimide into the Li-P bond, affording the lithium phosphaguanidinate salt Li[Ph2PC(NPr )2] in 72% yield. The preparation and reactivity of this new ligand are summarized in Scheme 217. An X-ray crystal structure analysis of the product obtained after removal of the solvent from the reaction mixture revealed the presence of a mono-solvated, centrosymmetric dimer in the solid state (Figure... 

Tris(ferf-butoxy)siloxide molecular precursors of V(IV) and V(V) can be prepared via simple silanolysis reactions. For example, OV[OSi(O Bu)3]3 was obtained in 85% yield by reaction of OVCI3 with excess HOSi(O Bu)3 in the presence of pyridine [79]. Although crystals of sufficient quality for an X-ray structural analysis of 0V[0Si(0 Bu)3]3 were not obtained, its identity was confirmed by various spectroscopic and analytical techniques. Additionally, ( BuO)3VOSi(O Bu)3 and ( BuO)2V[OSi(O Bu)3]2 were obtained via reaction of V(0 Bu)4 with 1 and 2 equiv of HOSi(O Bu)3, respectively, in toluene at 80 °C [80] (Eq. 5). Both (fBu0)3V0Si(0 Bu)3 and CBu0)2V[0Si(0 Bu)3]2 are monomeric in the solid state, and possess only monodentate siloxide ligands... 

Applications The general applications of XRD comprise routine phase identification, quantitative analysis, compositional studies of crystalline solid compounds, texture and residual stress analysis, high-and low-temperature studies, low-angle analysis, films, etc. Single-crystal X-ray diffraction has been used for detailed structural analysis of many pure polymer additives (antioxidants, flame retardants, plasticisers, fillers, pigments and dyes, etc.) and for conformational analysis. A variety of analytical techniques are used to identify and classify different crystal polymorphs, notably XRD, microscopy, DSC, FTIR and NIRS. A comprehensive review of the analytical techniques employed for the analysis of polymorphs has been compiled [324]. The Rietveld method has been used to model a mineral-filled PPS compound [325]. 

We also performed a single-crystal X-ray structure analysis of this lead compound. The solid state structure of this compound depicted in Fig. 3-15 shows a half-boat-like ( sofa ) conformation with the 9-phenanthryl group in a quasi-axial or r/Mf/.v/-flagpole position, and the a, 3-unsaturated exocyclic ester in a s-cis conformation. This cleft-like conformation is advantageous for the creation of centers with a high recognition ability, since one enantiomer fits in better than the other thus leading to selectivity. 

For the orientation-based structure analysis of MAPs, uniformly oriented lipid bilayers are typically prepared on solid supports as illustrated in Fig. 2 [23, 47, 55]. These mechanically oriented membranes are advantageous for static ssNMR experiments, as they provide a robust way to orient a sample with any desired lipid composition, peptide concentration, and at any desired temperature. The lipids... 

Wadhwani P, Strandherg E (2009) Structure analysis of membrane-active peptides using 19F-labeled amino acids and solid-state NMR. In Ojima I (ed) Fluorine in medicinal chemistry and chemical biology. Wiley, Chichester, pp 463-493... 

Wadhwani P, Tremouilhac P, Strandberg E, Afonin S, Grage S, Ieronimo M, Berditsch M, Ulrich AS (2007) Using fluorinated amino acids for structure analysis of membrane-active peptides by solid-state 19F-NMR. In Soloshonok V, Mikami K, Yamazaki T, Welch JT, Honek J (eds) Current fluoroorganic chemistry (ACS symposium series). American Chemical Society, Washington, pp 431 146... 

Afonin S, Mikhailiuk PK, Komarov IV, Ulrich AS (2007) Evaluating the amino acid CF3-bicyclopentylglycine as a new label for solid-state F-19-NMR structure analysis of membrane-bound peptides. J Pept Sci 13 614-623... 

Afonin S, Durr UHN, Wadhwani P, Salgado J, Ulrich AS (2008) Solid state NMR structure analysis of the antimicrobial peptide gramicidin S in lipid membranes concentration-depen-dent re-alignment and self-assembly as a beta-barrel. Top Curr Chem 273 139-154... 

Hydroxy-7-phenylindeno[l,2-A]-l,2,5-oxadiazolo[3,4- /]pyridine can have four polymorphic forms in the solid state, of which two are yellow and two are red. Two of them are interconvertible (yellow/red) upon exposure to different solvents. X-ray crystal structure analysis of one of the red forms shows the phenyl ring and the indenoox-adiazolopyridine ring to be coplanar <1999H(50)895>. 

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