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 π–π interactions. Additionally, in case of the aminophenyl compounds intra-as well as intermolecular hydrogen bonds are found that ...