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Yellow Crystals (yellow + crystal)
Selected AbstractsRole of oxygen vacancies in the coloration of 0.65Pb(Mg1/3Nb2/3)O3 -0.35PbTiO3 single crystalsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 5 2007Zhiguo Xia Abstract The coloration and oxygen vacancies in 0.65Pb(Mg1/3Nb2/3)O3 -0.35PbTiO3 (PMN-PT(65/35)) (starting composition) single crystals grown by a so-called modified Bridgman technique were investigated in this paper. Light yellow and dark brown colored crystals were generally observed for the typical as-grown PMN-PT(65/35) single crystals. X-ray diffraction results demonstrated that they were both of pure perovskite structure, but good electric properties were only obtained for the light yellow crystal. X-ray photoelectron spectroscopy (XPS) was used to investigate the electronic structure of its components. The O 1s photoelectron spectra of the dark brown colored crystals located at the higher binding energy side, which meant the existence of the more oxygen vacancies. It accordingly led to the formation of the low valence cations associated with the coloration of the crystals, which is also testified by the obtained X-ray photoelectron spectra of Ti and Nb. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Ba6Si6N10O2(CN2) , A Nitridosilicate with a NPO-Zeolite Structure Type Containing Carbodiimide IonsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2009Sandro Pagano Abstract A new precursor approach leading to NPO-zeolite analogous nitridosilicates with cavities containing carbodiimide ions is presented. The reaction of amorphous "Si(CN2)2" and barium in liquid sodium afforded Ba6Si6N10O2(CN2) as yellow crystals. The structure is a rare example of the NPO-zeolite framework type and the first nitridosilicate incorporating carbodiimide ions. The partially ordered integration of carbodiimide moieties in the channels leads to the formation of a superstructure (P, no. 174, a = 16.255(2), c = 5.4690(11) Å, Z = 3, R1 = 0.0299, 2139 data, 100 parameters) and merohedral twinning. A comprehensive structure solution is presented, taking all possible ordering variants and twin laws into account.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Organotin(IV) complexes with various donor ligands and their cytotoxicity against tumour cell lines.APPLIED ORGANOMETALLIC CHEMISTRY, Issue 12 2003Part(I): R2SnCl2 with Schiff bases; unusual CN bond cleavage of the bases, X-ray structures of the ionic products formed Abstract Several Schiff bases derived from salicylaldehyde and aminopyridines were found to coordinate with Me2SnCl2 in 1:1 or 1:2 (tin:base) molar ratio in diethylether, depending on the nature of the Schiff base used, to form complexes of the general formula Me2SnCl2·L or Me2SnCl2·2L respectively. These Schiff bases coordinate with Ph2SnCl2 in a similar manner, but if the reaction is carried out in chloroform or if the product formed in ether is dissolved in chloroform then colourless to pale yellow crystals precipitated. The latter were analysed and found to be due to the ionic compounds [H2NpyN,H+]2 [Ph2SnCl4]2, which were formed as a result of an unusual cleavage of the CN bond of the Schiff bases. The Schiff bases, their Me2SnCl2 complexes and the ionic compounds were analyzed physicochemically and spectroscopically. The crystal structures of two of the ionic compounds showed that the cation [H2NpyN,H+] binds with the anion [Ph2SnCl4]2, via hydrogen bonds. The Schiff bases, their Me2SnCl2 complexes and the ionic compounds were screened against the three tumour cell lines, L929, K562 and HeLa, and the results were compared with those of the anticancer drugs, cisplatin, carboplatin and oxaliplatin. Copyright © 2003 John Wiley & Sons, Ltd. [source] Red, orange and yellow crystals of 4,5-bis(4-methoxyphenyl)-2-(3-nitrophenyl)-1H -imidazoleACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2000Yoshinobu Inouye Red non-solvate crystals of the title compound from ethanol, C23H19N3O4, orange solvate crystals from tert -butanol, C23H19N3O4·C4H10O, yellow solvate crystals from dioxane,water, C23H19N3O4·0.5C4H8O2, and intense yellow solvate crystals from benzene,N,N,-dimethylformamide, C23H19N3O4·C6H6, differ from each other in their molecular conformation and hydrogen-bonding scheme. The bathochromic shifts of the crystal color are explained by the molecular planarity and charge-transfer effect among the imidazole molecules. [source] Polymorphism Versus Thermochromism: Interrelation of Color and Conformation in Overcrowded Bistricyclic Aromatic EnesCHEMISTRY - A EUROPEAN JOURNAL, Issue 12 2006P. Ulrich Biedermann Dr. Abstract The nature of the thermochromic form of overcrowded bistricyclic aromatic enes (BAEs) has been controversial for a century. We report the single-crystal X-ray structure analysis of the deep-purple and yellow polymorphs of 9-(2,7-dimethyl-9H -fluoren-9-ylidene)-9H -xanthene (11), which revealed the molecules in a twisted and a folded conformation, respectively. Therefore, the deeply colored thermochromic form B of BAEs is identified as having a twisted conformation and the ambient-temperature form A as having a folded conformation. This relationship between the color and the conformation is further supported by the X-ray structures of the deep-purple crystals of the twisted 9-(9H -fluoren-9-ylidene)-9H -xanthene (10), and of the yellow crystals of the folded 9-(11H -benzo[b]fluoren-11-ylidene)-9H -xanthene (12). Based on this conclusive crystallographic evidence, eleven previously proposed rationales of thermochromism in BAEs are refuted. In the twisted structures, the tricyclic moieties are nearly planar and the central double bond is elongated to 1.40 Å and twisted by 42°. In the folded structures, the xanthylidene moieties are folded by 45° and the fluorenylidene moieties by 18,20°. Factors stabilizing the twisted and folded conformations are discussed, including twisting of formal single or double bonds, intramolecular overcrowding, and the significance of a dipolar aromatic "xanthenylium-fluorenide" push,pull structure. [source] | ||||||||||