Supramolecular structures of aromatic 1,3,4-oxadiazole solids

Aromatic 1,3,4-oxadiazoles offer the possibility to construct new microelectronic devices due to their thermostability and their optical and electronic properties. In this paper a summary is presented of our previous results in determination of the supramolecular structure of thin poly(p-phenylene-1,3,4-oxadiazole)s (POD) films as well as of the crystal structures of low molecular weight aromatic 1,3,4-oxadiazoles. The use of a nitroalkane/Lewis acid mixture as a new solvent system for POD allows for the first time the preparation of thin POD films with a high degree of molecular order. It was also shown that these films can be electrochemically doped to obtain an electrically conducting polymer. The crystal structures of 2,5-di(tolyl)-1,3,4-oxadiazole (DTO) and 2,5-di(p-methoxycarbonyl-phenylene)-1,3, (DMPO) were determined by X-ray scattering, polarized FTIR spectroscopy and AFM. Whereas in DMPO the interactions of carbonyl groups are important for the crystallization process, the crystal growth in DTO is determined predominantly by the interactions between the aromatic rings.