Crystal structure determination by X-ray

FACE-CENTERED CUBIC STRUCTURE. An internal crystal structure. determined by X -rays, in which the equivalent points are ai the corners of the unit cell and at the centers of the six faces of a cube. 

Kinematical diffraction Diffraction theory in which it is assumed that the incident beam only undergoes simple diffraction on its passage through the crystal. No further diffraction occurs that would change the beam direction after the first diffraction event. This type of diffraction is assumed in most crystal structure determinations by X-ray diffraction. Kinematical theory is well applicable to highly imperfect crystals made up of small mosaic blocks. 

Very recently, these methods have resulted in the first crystal structure determination by X-ray diffraction of an integral membrane protein, the photosynthetic reaction centre of Rps. viridis [265]. 

The cluster (NiCp)3CCOOCH3 9 should also be included in the class (cyclo-pentadienyl)(alkylidyne)trinickel clusters. It was prepared in the reaction of Co3(CO)9CR with the known metal exchange reagent (CpNiCO)2. Its crystal structure determined by X-ray measurements is shown in Fig. 3. 

The development of the structural study of CyDs in the last century has been summarized in several reviews [1-7]. In 1942, the crystallographic method was first applied to CyDs to determine molecular weight [8j. James et al. proposed a packing structure [9] for several crystalline complexes of a-CyD with small guest molecules in 1959. Preliminary crystallographic data of y -CyD complexes with benzene derivatives were reported in 1968 [10]. The crystal structure first solved by X-ray analysis in 1965 was that of the a-CyD complex with potassium acetate [11]. Structures of two other well-known CyDs, fi-CyD [12] and y-CyD [13, 14], were determined in 1976 and 1980, respectively. An up-to-date list of crystal structures determined by X-ray and/or neutron diffraction is collected in the Cambridge Crystallographic Database (http //www.ccdc.cam.ac.uk/). 

Metal-phosphorus coordination complexes provide many elegant illustrations of the varied stereochemical requirements of the different metallic elements. Known compounds number many thousands, and a considerable number of these have had their detailed crystal structures determined by x-ray diffraction methods. In addition there is a vast literature of infra-red and NMR data on these complexes. 

Receptor 142 is capable of self-organizing in the presence of NaX (where X is a halide) into dimeric structure held together by Lewis acid interactions between two crown ether moieties and the Na. This allows a binding cleft to be formed between the urea groups, which is able to bind anions, for example, chloride as shown in the crystal structure determined by X-ray crystallography (Figure 37). ... 

Although in this section we have focused on problems that can be encountered in single-crystal structure determination by X-ray diffraction, and it is important to be aware of such problems, in the majority of cases the method is straightforward and problems are fortunately exceptions rather than the rule. Of all the... 

The first chemical compound to have its crystal structure determined by X-ray diffraction was NaCl (rock salt). The author of the study, which was published in 1913, was a young man of 23 years, William L. Bragg [7]. Two years later, he and his father, W. H. Bragg, shared the Nobel Prize in physics. 

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