TY - JOUR A1 - Emmerling, Franziska A1 - Orgzall, Ingo A1 - Dietzel, Birgit A1 - Schulz, Burkhard A1 - Larrucea, Julen T1 - Ordering the amorphous - Structures in PBD LED materials JF - Journal of molecular structure 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 Y1 - 2012 U6 - https://doi.org/10.1016/j.molstruc.2012.04.040 SN - 0022-2860 VL - 1030 IS - 23 SP - 209 EP - 215 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Hoffmann, Katrin A1 - Dietzel, Birgit A1 - Schulz, Burkhard A1 - Reck, Guenter A1 - Hoffmann, Angelika A1 - Orgzall, Ingo A1 - Resch-Genger, Ute A1 - Emmerling, Franziska T1 - Combined structural and fluorescence studies of methyl-substituted 2,5-diphenyl-1,3,4-oxadiazoles - Relation between electronic properties and packing motifs JF - Journal of molecular structure N2 - Prerequisite for the rational design of functional organic materials with tailor-made electronic properties is the knowledge of the structure-property relationship for the specific class of molecules under consideration. This encouraged us to systematically study the influence of the molecular structure and substitution pattern of aromatically substituted 1,3,4-oxadiazoles on the electronic properties and packing motifs of these molecules and on the interplay of these factors. For this purpose, seven diphenyl-oxadiazoles equipped with methyl substituents in the ortho- and meta-position(s) were synthesized and characterized. Absorption and fluorescence spectra in solution served here as tools to monitor substitution-induced changes in the electronic properties of the individual molecules whereas X-ray and optical measurements in the solid state provided information on the interplay of electronic and packing effects. In solution, the spectral position of the absorption maximum, the size of Stokes shift, and the fluorescence quantum yield are considerably affected by ortho-substitution in three or four ortho-positions. This results in blue shifted absorption bands, increased Stokes shifts, and reduced fluorescence quantum yields whereas the spectral position and vibrational structure of the emission bands remain more or less unaffected. In the crystalline state, however, the spectral position and shape of the emission bands display a strong dependence on the molecular structure and/or packing motifs that seem to control the amount of dye-dye-interactions. These observations reveal the limited value of commonly reported absorption and fluorescence measurements in solution for a straightforward comparison of spectroscopic results with single X-ray crystallography. This underlines the importance of solid state spectroscopic studies for a better understanding of the interplay of electronic effects and molecular order. KW - Diphenyl-oxadiazoles KW - X-ray structure KW - Packing motif KW - Optical properties KW - Fluorescence quantum yield Y1 - 2011 U6 - https://doi.org/10.1016/j.molstruc.2010.11.071 SN - 0022-2860 VL - 988 IS - 1-3 SP - 35 EP - 46 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Schulz, Burkhard A1 - Orgzall, Ingo A1 - Diez, Isabel A1 - Dietzel, Birgit A1 - Tauer, Klaus T1 - Template mediated formation of shaped polypyrrole particles N2 - The formation of different micro- and nanostructures during the chemical synthesis of polypyrrole is reviewed shortly based on the conceptions of hard- and soft-templating models. Contrary to other models that emphasize the role of micelles it is found here that during the oxidative polymerization of pyrole using sulfonic acid dopants a crystalline hard template is found in the first steps of the reaction before the addition of the oxidant. This template is formed by a complex consisting of 2,5-bis(pyrrole-2-yl)pyrrolidine and the sulfonic acid anion. The acid catalyzed formation of this specific tripyrrole is discussed. (C) 2009 Elsevier B.V. All rights reserved. Y1 - 2010 U6 - https://doi.org/10.1016/j.colsurfa.2009.11.034 SN - 0927-7757 ER - TY - JOUR A1 - Schulz, Burkhard A1 - Dietzel, Birgit A1 - Orgzall, Ingo A1 - Diez, Isabel A1 - Xu, Chenggang T1 - Aspects of morphology control during the oxidative synthesis of electrically conducting polymers N2 - The formation of micro- and nanostructures during the oxidative polymerization of polypyrrole and polyaniline is investigated using different sulfonic acid dopants. Rod- or tube-like structures are found in polypyrrole as well as in polyaniline without addition of further compounds to the initial reaction mixture of monomer, dopant and oxidant. In these cases, always a crystalline precursor complex composed of a dopand molecule and the pure monomer (aniline) or a trimeric moiety (pyrrole) serves as in-situ template. In most cases the surface of the growing polymer is covered by secondary structures with much smaller sizes so that a hierarchical order of structures at different length scales results. Corresponding model considerations for the polymerization process are outlined. Additionally, unusual structures like platelets, frames, rings, or ribbons are observed in the polypyrrole synthesis in the presence of fluorosurfactants. Y1 - 2009 UR - http://hip.sagepub.com/ U6 - https://doi.org/10.1177/0954008309339933 SN - 0954-0083 ER - TY - JOUR A1 - Karageorgiev, Peter A1 - Stiller, Burkhard A1 - Prescher, Dietrich A1 - Dietzel, Birgit A1 - Schulz, Burkhard A1 - Brehmer, Ludwig T1 - Modification of the surface potential of azobenzene-containing langmuir-blodgett films in the near field of a scanning kelvin microscope tip by irradiation Y1 - 2000 ER - TY - JOUR A1 - Stiller, Burkhard A1 - Karageorgiev, Peter A1 - Perez, E. A1 - Valez, M. A1 - Reiche, Jürgen A1 - Prescher, Dietrich A1 - Dietzel, Birgit A1 - Brehmer, Ludwig T1 - Scanning kelvin microscopy as a tool for visualisation of optically induced molecular switching in azobenzene self assembling films Y1 - 2000 SN - 0142-2421 ER - TY - JOUR A1 - Schrader, Sigurd A1 - Vismants, Z. A1 - Dietzel, Birgit A1 - Flueraru, C. A1 - Prescher, Dietrich A1 - Reiche, Jürgen A1 - Motschmann, H. A1 - Brehmer, Ludwig T1 - Linear and nonlinear optical properties of Langmuir-Blodgett multilayers from chromophore-containing maleic acid anhydride polymers Y1 - 1999 ER - TY - JOUR A1 - Janietz, Dietmar A1 - Katholy, Stefan A1 - Dietzel, Birgit A1 - Brehmer, Ludwig T1 - Monolayer behaviour of two-fold hydroxy terminated sheet-like Tetrakis(phenylethynyl) benzene derivatives Y1 - 1997 ER - TY - JOUR A1 - Reiche, Jürgen A1 - Schulz, Burkhard A1 - Knochenhauer, Gerald A1 - Dietzel, Birgit A1 - Freydank, Anke-Christine A1 - Zetzsche, Thomas A1 - Brehmer, Ludwig T1 - Supramolecular structures formed from heterocyclic aromatic molecules N2 - This paper describes the formation and structure investigation of Langmuir monolayers and Langmuir-Blodgett multilayers formed from amphiphilic derivatives of 2,5-diphenyl-1,3,4-oxadiazole. The 2,5-diphenyl-1,3,4-oxadiazole group as a functional unit with interesting physical and chemical properties is maintained, while the head group, the length of the alkyl chain and the structure of the coupling unit between aromatic and aliphatic part of these linear short-chain amphiphiles is systematically varied in order to explore the influence of this change on the film forming properties and the stability of Langmuir and Langmuir-Blodgett films. Molecular mechanics simulations are shown by these systematic variations to be suitable for the prediction of optimal chemical structures allowing for a stable stratified molecular packing. The combination of a detailed structure investigation of the multilayers based on scanning force microscopy and X-ray data with molecular mechanics simulations yields an insight into the packing of the molecules and the intermolecular interactions. Y1 - 1997 ER - TY - JOUR A1 - Reiche, Jürgen A1 - Freydank, A. A1 - Dietzel, Birgit A1 - Katholy, Stefan A1 - Knochenhauer, Gerald A1 - Zetzsche, Thomas A1 - Schulz, Burkhard A1 - Brehmer, Ludwig T1 - Komplexe Strukturanalytik von Oxadiazol-Mono- und Multischichten Y1 - 1995 ER -