Yield single crystal

For many molecular materials, crystallization from solution does not yield single crystals of suitable size and quality for single-crystal XRD, and instead produces only microcrystalline powders. In such cases, structure determination from powder XRD data provides a viable route for establishing structural understanding of the resultant materials. 

The first example of using x-ray diffraction techniques to record the structure of partially reacted crystals was reported by Nakanishi et al. in 1980. They monitored the dimerization of 2-benzyl-5-benzylidenecyclopentanone (28) and 2-benzyl-5-p-bromobenzylidenecyclopentanone (29) [112,113]. Both compounds were photolyzed to yield single crystals of product which were isostructural with recrystallized dimer [114]. Compound 29 (Scheme 20), which has a particularly... 

Scheme 4 1 Crystallization of the hydrated zwitterion [CoIII(r 5-C5H4COOH)(r 5-C5H4 COO)] 3H20(ZW 3H20) from its aqueous solution. 2 The dehydration process yields crystalline powder of the anhydrous form [CoIII(r 5-C5H4COOH)(r 5-C5H4COO)] (ZW). 3 Seeding of the original solution with powder of ZW. 4 The seeding process yields single crystals of ZW [39],...

Hydrofluoric acid (bp, 19.5°C Tc, 188°C Pc, 64 atm), nitrogen dioxide (bp, 21°C Tc, 158.2°C Pc, 100 atm in equilibrium with N2O4), sulfuric acid (decomposition at 280°C), and polyphosphoric acid are candidates for solvents in solvothermal reactions, and the reactions of these solvents will produce a variety of products that cannot be prepared by any other methods. For example, Bialowons et al. reported that solvothermal treatment of (02)2Ti7F3o in anhydrous HF at 300°C yielded single crystals of TiF4. Solvothermal reactions in these solvents may produce fruitful results and a new field seems to be awaiting many researchers. 

Optical activity was first studied in compounds of carbon. In 1874 van t Hoff showed how optical activity could arise if the four bonds from a carbon atom were arranged tetrahedrally. Le Bel independently, and almost simultaneously, put forward somewhat similar views. A molecule Cubed in which a C atom is attached to four different atoms or groups should exist in two forms related as object and mirror image. The central C atom was described as an asymmetric C atom. A simple molecule of this sort is that of lactic acid, CH(CH3XOH)COOH, which exists in d- and /-forms. There is a third form of such a compound, the racemic form. A true racemate has a characteristic structure different from that of the active forms, there being equal numbers of d- and /-molecules in the unit cell of the crystal, which is optically inactive. We may note that inactive crystalline forms of optically active compounds are not necessarily racemates. For example, the inactive 3-phenylglyceric acid (m.p. 141°C) is not a racemate but the crystals are built of submicroscopic lamellae which are alternately d- and /-rotatory. Slow recrystallization yields single crystals of the d- and /-forms (m.p. 164°C).( ... 

Aluminum nitride was synthesized from ammonia using the gas-transport reaction method. This yielded single-crystal "whiskers" about 1-2 mm long and a few tenths of a millimeter in diameter. The x-ray diffraction study was carried out on transparent single crystals (whiskers)... 

When phenyltri(methoxy)silane was reacted with water in the presence of sodium hydroxide (Si Na H20= 1.0 1.0 1.0) in /-propanol or /-butanol, all-cis-Ph-T4-tetrol was formed. Meanwhile, when phenyltrimethoxysilane (0.24 mol) was treated with sodium hydroxide in the molar ratio of Si sodium= 2 1 at the refluxing temperature of /-propanol (240 mL) for 4h under nitrogen, a crystalline compound was formed." " After 40 h of stirring, a product with 1379.47m/z (calculated 1379.24) and two Si signals at —76.12 and —78.94 (Os /Ph) was obtained after trimethylsilyl (TMS) capping, which was determined as tetrakis (TMS)-Ph-Tg-tetrol (68.2% yield). Single crystal XRD analysis of the compound after neutralization conhrmed the double-decker structure. The XRD structure is shown in Figure 4.18. 

For many polymers, crystal growth can take place either from the melt or from dilute solution to yield single crystals. Crystal formations in polymers were studied intensively almost from the time of recognition of their existence in macromolecules. As a result, certain basic principles were established (1) The melt crystallization process is a first-order phase transition (see Section 1.4.5). (2) Crystallization from a molten polymer follows the general mathematical formulation for the kinetics of a phase change.Equilibrium conditions, however, are seldom if ever attained and complete crystallinity is not reached. 

Metal particle catalyzed chemical vapor deposition is the most versatile VLS process (Table II) yielding a wide range of single crystal whiskers and nanowhiskers [1-2] [5-6], short amorphous or polycrystalline fibers [1] [7], and nanotubes [8]. Laser ablation of selected metal alloys is a recent VLS process used for the synthesis of semiconductor nanowire [74]. Metal particle catalyzed carbothermal reduction, another VLS process, yields single crystal whiskers [9-10]. Metal catalyzed arc discharge [11], metal particle catalyzed laser ablation [12], and metal particle catalyzed plasma arc discharge [13] yield nanotubes by a VLS mechanism. 

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