Systematic structural analysis of a series of anion receptor complexes

A crystallographic systematic study of a series of 6 anion receptor complexes has been performed, with the accurate atomic positions and displacement parameters of the hydrogen atoms for two complexes determined by neutron diffraction studies. The N-H center dot center dot center dot anion hydrogen bonding interaction is shown to be central to the geometry of the urea unit. Contributions of the intermolecular interactions to the packing of the molecule are highlighted by correlation to the Hirshfeld surfaces and their fingerprint plots, with alterations to the position and amount of nitro substitution on the receptor shown to affect the pi center dot center dot center dot pi stacking motifs observed across the structures.