Crystal engineering with 1,3,4-oxadiazole derivatives: on the importance of CH?N and CH? interactions

Three new 1,3,4-oxadiazoles (1-3) have been synthesized. The crystal structure of two of them were solved by single crystal X-ray diffraction analysis and a detailed quantitative analysis of the weak noncovalent interactions have been performed by using DFT calculations. In both compounds, the formation of recurrent H-bonded motifs involving the 1,3,4-oxadiazole is observed. In addition, a variety of CHMIDLINE HORIZONTAL ELLIPSIS pi interactions are established, involving both aliphatic and aromatic C-H bonds and the pi-system of the electron rich tert-butylphenyl ring. QTAIM analysis and NCI plots were used to study the nature and the extent of different intermolecular interactions observed in these structures, which were rationalized using MEP surface plots. A detailed quantitative analysis of the weak noncovalent interactions in the X-ray structures of 1,3,4-oxadiazoles has been performed by using the DFT calculations.