Search results for "Crystal"
showing 10 items of 22886 documents
Single-Crystal Structures of Model Compounds for Poly(2,5-dialkoxy-1,4-phenylenevinylene)
1999
Die kristallstruktur von oligo[(2-hydroxy-1,3-phenylen)methylen]en
1984
The crystal structure of three tetranuclear phenolic compounds – 6,6′-bis (2-hydroxy-5-methylbenzyl)-4,4′-dimethyl-2,2′-methylenediphenol (1), 6-(2-hydroxy-3,5-dimethylbenzyl)-6′-(2-hydroxy-5-methylbenzyl)-4,4′-dimethyl-2,2′-methylendiphenol (2), and 6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-6′-(2-hydroxy-5-methylbenzyl)-4,4′-dimethyl-2,2′-methylene-diphenol (3) –, was determined by single crystal X-ray analysis. Intramolecular hydrogen bonds between all hydroxyl groups of adjacent phenolic units are found for all molecules. They are directed to the opposite end of the molecule by the ortho-methyl or ortho-tert-butyl group in compounds 2 and 3, while no special orientation is found in 1. Th…
N-(3H-Thiazol-2-ylidene)nitramine and N-methyl-N-(thiazol-2-yl)nitramine
2003
The geometries of the thiazole ring and the nitramino groups in N-(3H-thiazol-2-ylidene)nitramine, C 3 H 3 N 3 O 2 S, (I), and N-methyl-N-(thiazol-2-yl)nitramine, C 4 H 5 N 3 O 2 S, (II), are very similar. The nitramine group in (II) is planar and twisted along the C-N bond with respect to the thiazole ring. In both structures, the asymmetric unit includes two practically equal molecules. In (I), the molecules are arranged in layers connected to each other by N-H...N and much weaker C-H...O hydrogen bonds. In the crystal structure of (II), the molecules are arranged in layers bound to each other by both weak C-H...O hydrogen bonds and S...O dipolar interactions.
Approaches to the preparation of carborane-containing carbosilane compounds.
2005
[Structure: see text] A novel type of carborane cluster assembly has been successfully prepared using carbosilane derivatives as a scaffold. Two synthetic routes have been used: One involves the reaction of a carbosilane containing terminal Si-Cl functions with the lithium salt of the phenyl-o-carborane, and the second one consists of a highly efficient hydrosilylation of tetravinylsilane with the corresponding carboranylsilane. The crystal structure of this carborane-containing carbosilane compound has been determined by X-ray diffraction.
Special Calixarenes by Directed Syntheses
1997
The synthesis of special calixarenes and calixarene-like macrocyclic compounds via stepwise procedures and fragment condensation is reviewed. Among the compounds available are exo- and endo-calixarenes consisting of different phenolic units, having bridges other than methylene or showing inherent chirality (Cn-symmetry). Macrobi- and -tricyclic molecules such as bridged calixarenes, double calixarenes, bicyclocalixarenes and annelated calixarenes are also described. Single crystal X-ray structures are reported for several compounds. Some properties like conformational barriers, pKa values or the ability to complex metal ions are discussed, showing the potential of these compounds which may …
Racemattrennung, Kristallstruktur und histaminartige Wirkung von 4-[1-(2-Aminoethylthio)ethyl]-5-methylimidazol
1983
Es wird die Racemattrennung von 4-[1-(2-Aminoethylthio)ethyl]-5-methylimidazol (1) mittels optisch aktiver Di-O-(p-toluoyl)weinsaure sowie die histaminartige Wirksamkeit der Enantiomeren beschrieben. Von (+)-1 · 2HCl · H2O wurde die Kristallstruktur bestimmt und bis zu einem R-Wert von 0.0483 verfeinert. Danach ist (+)-1R-konfiguriert. Von den beiden Enantiomeren besitzt nur (S)-(−)-1 H1-agonistische Aktivitat. Resolution, Crystal Structure, and Histamine-like Activity of 4-[1-(2-Aminoethylthio)ethyl]-5-methylimidazole The resolution of racemic 4-[1-(2-aminoethylthio)ethyl]-5-methylimidazole (1) using optically active Di-O-(P-toluoyl)tartaric acid as well as the histamine-like activity of t…
Indoloquinolines, Indolobenzoxazines and Quinazolophthalazines Prepared from Norbornane/eneamino Acids and Hydrazides
2005
The reactions of di-endo- and di-exo-aminonorbornane/enecarboxylic acids 1–4 with ethyl 2-(2-oxocyclohexyl)acetate afforded methanoindoloquinolines 5, 6, 8, and 9, the oxo ester participating as a two-membered sp2 building block. In the cases of di-exo- and di-endo-aminonorbornenecarboxylic acids 2 and 4, methanoindolobenzoxazinediones 7 and 10 were also formed; compound 7 was also isolated from the mother liquor of 10. The reactions of ethyl 2-(2-oxocyclohexyl)acetate with aminonorbornane/enecarbohydrazides 11–14 result in the methanoquinazolophthalazines 15–18. The structures of the compounds were elucidated by NMR spectroscopy, and for 6, 7, 8, and 10 also by X-ray crystallography. (© Wi…
Mechanism of redox transformation of titanocene dichloride centers immobilized inside a polypyrrole matrix—EQCM and XPS evidences
2005
Abstract We report electrochemical quartz crystal microbalance (EQCM) results for electrodeposition of titanocene derivatized polypyrrole p(Tc3Py) films and redox transformation of polypyrrole matrix and titanocene centers immobilized in the film. Films of p(Tc3Py), Tc3Py = Tc(CH 2 ) 3 NC 4 H 4 (Tc = Cl 2 TiCpCp′, Cp = C 5 H 5 , Cp′ = C 5 H 4 ) were obtained from acetonitrile solutions of monomer on a Pt disc or thin Au layer evaporated on 10 MHz quartz crystals. Polymerization efficiency, derived from the slope of the change of resonant frequency as a function of the deposition charge ranged from 54% to 75%. A gradual loss of redox activity of Tc centers during consecutive redox cycles of …
The Photocatalytic Activity of Novel, Substituted Porphyrin/TiO2-Based Composites
2010
Four novel porphyrins, 5-[3-(3-phenoxy)-propoxy]phenyl porphyrin, 5,15-di-[3-(3-phenoxy)-propoxy] phenyl porphyrin, 5,10,15-tri-[3-(3-phenoxy)-propoxy]phenyl porphyrin, 5,10,15,20-tetra-[3-(3-phenoxy)- propoxy]phenyl porphyrin, and their corresponding Cu(II) porphyrins, were synthesized and characterized spectroscopically. The photodegradation of 4-nitrophenol in aq. suspension was used to determine the photocatalytic activity of polycrystalline TiO2 samples which had been impregnated with the Cu(II) porphyrins, as sensitizers. The photocatalytic activity of the composite depends mainly on the amount of sensitizer on the TiO2 surface rather than the nature of the substituted porphyrins.
2,2′-Dimethyl-2,2′-(m-phenylenedimethylene)propanedinitrile
2009
The title compound, C16H14N4, features an aromatic ring with two 2,2´-dicyanopropyl residues in positions 1 and 3, which are located above and below the ring plane. The two residues differ in their conformation with respect to the aromatic ring: whereas one of the Cmethyl-C-Cmethylene-Caromatic torsion angles is gauche [68.93 (12)°], the other one is fully staggered [177.63 (9)°]. The crystal structure is stabilized by C-H...N hydrogen-bonding interactions. Key indicators: single-crystal X-ray study; T = 173 K; mean σ(C–C) = 0.002 Å; R factor = 0.037; wR factor = 0.101; data-to-parameter ratio = 15.0.