TY  - JOUR
A1  - Franco, Olga
A1  - Orgzall, Ingo
A1  - Reck, Günter
A1  - Stockhause, Sabine
A1  - Schulz, Burkhard
T1  - Structure and high-pressure behavior of 2,5-di-(4-aminophenyl)-1,3,4-oxadiazole
N2  - The crystalline structures of two modifications of a compound containing the oxadiazole ring, 2,5-di-(4- aminophenyl)-1,3,4-oxadiazole (DAPO) were determined. One of these modifications contains water molecules in the crystal structure, which is observed for the first time for an oxadiazole crystal. Both crystals show an orthorhombic structure. The water free modification, DAPO L belongs to the space group Pbca (61) and has the lattice parameters: a = 13.461(5), b = 7.937(3) and c = 22.816(8) angstrom (CCDC 246608). The water containing pseudo-polymorph, DAPO 11, has the space group Cmcm (63) and the lattice parameters: a = 16.330(5), b = 12.307(2) and c = 6.9978(14) angstrom (CCDC 246609). To gain information on the inter molecular interactions within the crystals, X-ray experiments under compression at ambient temperature and under heating at vacuum conditions were performed. Neither DAPO I nor DAPO II undergo phase transitions in the ressure range up to 5 GPa, as could be concluded from X-ray and Raman experiments. X-ray and calorimetric studies indicate that DAPO II dehydrates into DAPO I under increasing temperature. Structural considerations suggest a two-stage process. The compression behavior of both substances is well described by the Murnaghan equation of state (MEOS) and the values of the bulk modulus and its pressure derivative are determined for these crystals. Additionally, in the case of DAPO I, also the thermal expansion coefficient an was measured. (c) 2005 Elsevier Ltd. All rights reserved
Y1  - 2005
SN  - 0022-3697
ER  - 
TY  - JOUR
A1  - Emmerling, Franziska
A1  - Orgzall, Ingo
A1  - Reck, Günter
A1  - Schulz, Burkhard W.
A1  - Stockhause, Sabine
A1  - Schulz, Burkhard
T1  - Structures of substituted di-aryl-1, 3,4-oxadiazole derivatives: 2,5-bis(pyridyl)- and 2,5-bis(aminophenyl)-substitution
JF  - Journal of molecular structure
N2  - Crystal structures of four different di-aryl-1,3,4-oxadiazole compounds (aryl = 2-pyridyl-, 3-pyridyl-, 2-aminophenyl-, 3-aminophenyl-) are determined. Crystallization of di(2-pyridyl)-1,3,4-oxadiazole yielded monoclinic and triclinic polymorphs. The structures are characterized by the occurrence of pi-pi interactions. Additionally, in case of the aminophenyl compounds intra- as well as intermolecular hydrogen bonds are found that influence the packing motif as well. Since these molecules are often used as ligands in metal-organic complexes similarities and differences of the molecular conformation between the molecules in the pure crystals and that of the ligands in the complexes are discussed. (c) 2006 Elsevier B.V. All rights reserved.
KW  - crystal structure
KW  - 1,3,4-oxadiazole
KW  - molecular conformation
KW  - hydrogen bonds
Y1  - 2006
U6  - https://doi.org/10.1016/j.molstruc.2006.03.076
SN  - 0022-2860
VL  - 800
IS  - 1-3
SP  - 74
EP  - 84
PB  - Elsevier
CY  - Amsterdam
ER  -