ChemInform Abstract: SODIUM PHOSPHATE: EXPERIMENTS ON PURIFICATION AND CRYSTAL STRUCTURE OF THE HIGH-TEMPERATURE FORM

1980 ◽  
Vol 11 (25) ◽  
Author(s):  
D. M. WIENCH ◽  
M. JANSEN
1987 ◽  
Vol 13 (5) ◽  
pp. 260-270 ◽  
Author(s):  
A. KAWAHARA ◽  
Y. ANDOU ◽  
F. MARUMO ◽  
M. OKUNO

Author(s):  
Christoph Krebs ◽  
Inke Jess ◽  
Christian Näther

Single crystals of the high-temperature form I of [Co(NCS)2(DMAP)2] (DMAP = 4-dimethylaminopyridine, C7H10N2) were obtained accidentally by the reaction of Co(NCS)2 with DMAP at slightly elevated temperatures under kinetic control. This modification crystallizes in the monoclinic space group P21/m and is isotypic with the corresponding Zn compound. The asymmetric unit consists of one crystallographically independent Co cation and two crystallographically independent thiocyanate anions that are located on a crystallographic mirror plane and one DMAP ligand (general position). In its crystal structure the discrete complexes are linked by C—H...S hydrogen bonds into a three-dimensional network. For comparison, the crystal structure of the known low-temperature form II, which is already thermodynamically stable at room temperature, was redetermined at the same temperature. In this polymorph the complexes are connected by C—H...S and C—H...N hydrogen bonds into a three-dimensional network. At 100 K the density of the high-temperature form I (ρ = 1.457 g cm−3) is lower than that of the low-temperature form II (ρ = 1.462 g cm−3), which is in contrast to the values determined by XRPD at room temperature. Therefore, these two forms represent an exception to the Kitaigorodskii density rule, for which extensive intermolecular hydrogen bonding in form II might be responsible.


2009 ◽  
Vol 65 (4) ◽  
pp. 416-425 ◽  
Author(s):  
Pascal Roussel ◽  
Olfa Labidi ◽  
Marielle Huve ◽  
Michel Drache ◽  
Jean-Pierre Wignacourt ◽  
...  

A new polymorph of Pb2BiVO6 was prepared under ambient conditions and its crystal structure was determined by single-crystal X-ray diffraction. The phase transitions α → β and β → δ were identified in the mother phase; the high-temperature form δ-Pb2BiVO6 eventually decomposes at 753 K to a mixture of Pb4BiVO8 and the high-temperature form of PbBiVO5 before showing recombination at 923 K. β-Pb2BiVO6 has an incommensurate monoclinic modulated structure. This crystal structure is twinned and complementary structural investigations of a powder sample of β-Pb2BiVO6 by TEM diffraction studies confirmed the lattice and incommensurate modulation character. Log σ = f(T −1) dependences for Pb2BiVO6-related materials (6% M-for-V-substituted compositions; M = Cr, Mn, P) are reported, which allow the characterization (E a and isothermal σ values) of the β- as well as the δ- and α-Pb2BiVO6 varieties.


1970 ◽  
Vol 24 ◽  
pp. 1477-1479 ◽  
Author(s):  
K. O. Strømme ◽  
Jean Galy ◽  
Karl-Axel Wilhelmi ◽  
A. Nørlund Christensen ◽  
S. E. Rasmussen ◽  
...  

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