A series of novel, acyclic pyrrole-based anion receptors is described that bind nitrite and carboxylate anions with good selectivity in dichloroethane solution. These systems, which are based on pyridine 2,6-dicarboxamides, also bind cyanide anions weakly. Control systems, incorporating a benzene-1,3-dicarboxamide spacer or wherein the connectivity of the amide linkage is ``reversed'', either failed to act as effective anion receptors or displayed very different selectivities.
Sessler, J. L., Barkey, N. M., Pantos, G. D., & Lynch, V. M. (2007). Acyclic pyrrole-based anion receptors: design, synthesis, and anion-binding properties. New Journal of Chemistry, 31(5), 646-654. https://doi.org/10.1039/b615673h