Role of lone pair- π interaction and halogen bonding in the crystal packing of 1,2,4-oxadiazole derivatives

Abstract

A comprehensive inspection of crystal packing of a series of four (5-chloro-2-((3-phenyl-1,2,4-oxadiazol-5-yl)methoxy)phenyl)methanone derivatives, containing biologically active 1,2,4-oxadiazol moiety, have been performed to investigate the functional role of non-covalent interactions in their supramolecular architectures. The compounds of interest are (5-chloro-2-((3-(4-iodophenyl)-1,2,4-oxadiazol-5-yl)methoxy)phenyl)(phenyl)methanone, C22H15O3N2ICl, OX-1, (5-chloro-2-((3-(3-chloro-4-fluorophenyl)-1,2,4-oxadiazol-5-yl)methoxy)phenyl)(phenyl)methanone, C22H14O3N2Cl2F, OX-2, (5-chloro-2-((3-(4-isopropylphenyl)-1,2,4-oxadiazol-5-yl)methoxy)phenyl)(phenyl)methanone, C25H21O3N2Cl, OX-3, (5-chloro-2-((3-(4-ethoxyphenyl)-1,2,4-oxadiazol-5-yl)methoxy)phenyl)(phenyl)methanone, C24H20O4N2Cl, OX-4. Title compounds were synthesized and subsequently characterised using the single crystal X-ray diffraction technique. In the crystal environment, the molecular conformations of all the four derivatives have been found to be stabilized via O⋯C [lone pair (lp)-π interaction] contacts. Detailed supramolecular structural analysis depicts an important role of lp-π interactions and halogen bonds in the crystal packing of all four derivatives in addition to the presence of favourable C-H⋯O, C-H⋯N, C-H⋯F and C-H⋯Cl hydrogen bonds. Furthermore, the electrostatic potential map provides a deeper insight to the nature of lp-π and halogen bonding interaction. The fingerprints plots associated with Hirshfeld surface were also analysed to evaluate the quantitative contribution of atom-atom contacts toward the formation of solid-state architectures. The quantitative analysis of the interaction energies associated with the molecular pairs involving lp-π and halogen bonding interactions has also been performed to get a deeper insight into the role of such interactions towards the overall stabilization of the crystal lattice.