Role Of Lone Pair- Pi Interaction And Halogen Bonding In The Crystal Packing Of 1,2,4-Oxadiazole Derivatives

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, C22H15O3N2ICI, OX-1, (5-chloro-2-(3-(3-chloro-4-fluorophenyl)-1,2,4-oxadiazol-5-yl)methoxy)phenyl)(phenyl)methanone, C22H15O3N2Cl2F, OX-2, (5-chloro-24(3-(4-isopropylphenyl)-1,2,4-oxadiazol-5-yl)methoxy)phenyl)(phenyl)methanone, C25H21O3N2Cl, OX-3, (5-chlo ro-24(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 center dot center dot center dot C [lone pair (lp)-pi interaction] contacts. Detailed supramolecular structural analysis depicts an important role of lp-pi interactions and halogen bonds in the crystal packing of all four derivatives in addition to the presence of favourable C-H center dot center dot center dot O, C-H center dot center dot center dot N, C-H center dot center dot center dot F and C-H center dot center dot center dot Cl hydrogen bonds. Furthermore, the electrostatic potential map provides a deeper insight to the nature of lp-pi 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-pi 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. (C) 2019 Elsevier B.V. All rights reserved.