TY - JOUR A1 - Franco, O. A1 - Reck, Günter A1 - Orgzall, I. A1 - Schulz, Burkhard A1 - Schulz, B. T1 - Characterization of a new non-centrosymmetric polymorph of diphenyl-1,3,4-oxadiazole N2 - Diphenyl-1,3,4-oxadiazole (DPO) crystallization experiments from solutions clearly reveal the polymorphism of the substance. Besides the formerly known centrosymmetric monoclinic structure with space group P21/c (DPO I) a new monoclinic structure with the non-centrosymmetric space group Cc is found (DPO II): a=2.4134(4) nm, b=2.4099(3) nm, c=1.2879(2) nm,?=110.048(3)°, and V=7.0363(17) nm3. The asymmetric unit contains six independent molecules in a complex packing motif. A re-determination of the crystal structure of DPO I at room temperature gives lattice parameters a=0.51885(6) nm, b=1.8078(2) nm, c=1.21435(14) nm, ?=93.193(3)°, and V=1.1373(2) nm3. X-ray measurements at 363 K show a significant increase of the unit cell volume by 1.6%. Differences between both structures concerning morphology and characteristic Raman bands are outlined in detail. DSC investigations show an irreversible transition from DPO I to DPO II at 97 °C. DPO II does not show any transition in the temperature range up to the melting point at 141 °C. The non-centrosymmetric DPO II structure shows triboluminescence. KW - Diphenyl-1,3,4-oxadiazole KW - X-ray structure KW - Polymorphism KW - Non-centrosymmetric structure PY - 2003 U6 - https://doi.org/10.1016/S0022-2860(02)00569-0 SN - 0022-2860 SN - 1872-8014 SN - 0377-046X VL - 649 SP - 219 EP - 230 PB - Elsevier CY - Amsterdam AN - OPUS4-2465 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Orgzall, I. A1 - Emmerling, Franziska A1 - Schulz, B. A1 - Franco, O. T1 - High-pressure studies on molecular crystals - relations between structure and high-pressure behavior N2 - This paper summarizes attempts to understand structure–property relationships for a large class of aromatic diphenyl-1,3,4-oxadiazole molecules. Starting from the investigation of the crystal structure several common packing motifs as well as characteristic differences are derived. Many different molecules show a rather planar conformation in the solid state. A stronger intermolecular twist is only observed for compounds with substituents occupying the ortho-positions of the phenyl rings. Most crystal structures are characterized by the formation of stacks leading to intense π–π acceptor–donor interactions between oxadiazole and phenyl rings. High-pressure investigations result in a soft compression behavior typical for organic molecular crystals. The bulk behavior may be described by the Murnaghan equation of state with similar coefficients (bulk modulus and its pressure derivative) for nearly all investigated compounds but also for related substances. The compression shows a strong anisotropy resulting from the specific features and packing motifs of the crystal structure. This is clearly indicated by a corresponding strain analysis. Additionally to the crystal structure the Raman spectrum was also investigated under increasing pressure. The different pressure behavior of external and internal modes reflects the difference between intra- and intermolecular interactions. KW - Diphenyl-1,3,4-oxadiazole KW - Crystal structure KW - High pressure investigations KW - Equation of state KW - Strain analysis KW - Raman investigations PY - 2008 U6 - https://doi.org/10.1088/0953-8984/20/29/295206 SN - 0953-8984 SN - 1361-648X VL - 20 SP - 295206-1 - 295206-15 PB - IOP Publ. Ltd. CY - Bristol AN - OPUS4-17784 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Emmerling, Franziska A1 - Orgzall, I. A1 - Dietzel, B. A1 - Schulz, B. A1 - Larrucea, J. T1 - Ordering the amorphous - Structures in PBD LED materials N2 - The class of 2,5 disubstituted-1,3,4-oxadiazoles containing a biphenyl unit on one side is intensively used as electron transport materials to enhance the performance of organic light emitting diodes (OLEDs). In contrast to the ongoing research on these materials insights in their structure-property relationships are still incomplete. To overcome the structural tentativeness and ambiguities the crystal structures of 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole, that of the related compound 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole and of 2-(4-biphenylyl)-5-(2,6-dimethylphenyl)-1,3,4-oxadiazole are determined. A comparison with the results of GAUSSIAN03 calculations and similar compounds in the Cambridge Structural Database leads to a profound characterization. KW - OLED KW - PBD KW - Diphenyl-1,3,4-oxadiazole KW - Crystallization PY - 2012 U6 - https://doi.org/10.1016/j.molstruc.2012.04.040 SN - 0022-2860 SN - 1872-8014 SN - 0377-046X VL - 1030 SP - 209 EP - 215 PB - Elsevier CY - Amsterdam AN - OPUS4-27264 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -