Complexation X-ray diffraction

Very recently a new method was developed that opens the possibility to polymerize even hydrophobic monomers in aqueous solution. This method is based on the finding that hydrophobic monomers can be made water-soluble by incorporation in the cavities of cyclodextrins. It has to be mentioned that no covalent bonds are formed by the interaction of the cyclodextrin host and the water-insoluble guest molecule. Obviously only hydrogen bonds or hydrophobic interactions are responsible for the spontaneous formation and the stability of these host-guest complexes. X-ray diffraction pattern support this hypothesis. Radical polymerization then occurs via these host-guest complexes using water-soluble initiators. Only after a few percent conversion the homogeneous solution becomes turbid and the polymer precipitates. 

Organometalhc complexes of technetium-99 can be studied by the traditional physical tools used in chemistry. Techniques hke infrared, multinuclear magnetic resonance, and mass spectroscopies, as well as magnetic susceptibility (to determine the number of unpaired electrons and thus the oxidation state) and X-ray crystallography are the main methods to study these complexes. X-ray diffraction methods are particularly important since only one small crystal is needed to determine the complete structure of the compound. 

Many other amylose complexes are water-insoluble, and the complexes with methanol, 1-propanol, acetone, and butanone may be precipitated from solutions of amylose in methyl sulfoxide, as well as from aqueous solution. As amylose frequently forms crystalline complexes. X-ray diffraction patterns have been obtained for a number of them. Amylose-methyl sulfoxide complexes have a structure almost identical to those of amylose-ethylenediamine complexes, in which the complexing ratio is one ethylenediamine molecule per two n-glucose residues. The helix packing-diameter of the complexes, at least for complexes with linear aliphatic ketones, is dependent upon the chain-length of the molecule complexed, although other factors are also involved. ... 

Fig. 29. Regions of homogeneity of the NaCl-type vacant yttrium oxy-carbide Y-(0, C, ) showing the redistribution of the initial composition of the pellets among the phases formed after thermal treatment at 900-1200°C (Brozek et al. 1985). A, initial elemental composition of the pellet 9, elemental composition of the Y-(0, C, ) phase x, additional phase exhibiting rather complex X-ray diffraction patterns.

Hydration of lanthanide complexes. X-ray diffraction studies of the solid complexes of KLn(EDTA)(H20),c showed the number of water molecules in the coordination sphere to be three for the lighter lanthanides and two for the heavier ones for total coordination numbers of nine and eight, respectively, since EDTA is hexadentate (Hoard et al. 1967). Ots (1973) measured a maximum at europium for the heat capacity change AC° for the formation of lanthanide-EDTA complexes. This maximum was taken as a strong evidence for hydration equilibrium between the complexed species,... 

Polyion complex technique is a unique method of supramolecular polymerization of bilayer membranes without conventional polymerization procedures [14,50], Water-insoluble polyion complexes are precipitated when the aqueous solution of the charged bilayer membrane is mixed with a water solution of the countercharged polyelectrolyte. The polyion complexes can be formed as thin films by usual casting from organic solutions. The fundamental bilayer structure and characteristics are essentially maintained in the immobilized cast films of the polyion complexes. X-ray diffraction of the solvent cast polyion complex films reveals the layered structure with repeating spacing corresponding to the bilayer thickness [50-52]. 

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