(Pyrazinecarbonyl)hydrazone halobenzaldehydes: supramolecular arrays generated by face to face stacking of ribbons, formed from C–H–O interactions

Abstract

The crystal structures of seven (pyrazinecarbonyl)hydrazone mono-halo-benzaldehyde derivatives, N2C4H3CONHN=CHC6H4X (X = F, Cl or Br) are reported. In all cases, hydrogen-bonds link the planar molecules edge to edge to form ribbons which are themselves essentially planar. These ribbons are then packed face to face in a variety of ways dependent upon the position and nature of the halogen substituent. In all of the structures the molecules are found in layers one molecule thick. For the chloro- and bromo-substituted compounds three distinct forms of two-dimensional connectivity in the layers is achieved by combination of π · · · π interactions with the ribbon hydrogen-bonds. For the fluoro- derivatives the ribbon hydrogen-bonds connect layers in which the two-dimensional connectivity is provided by the π · · · π interactions, in one case augmented by C–H · · · F and C–H · · · π bonds, resulting in complete three-dimensional connectivity.