Two easy-to-synthesize polypyrrolic 2,5-diamidothiophene Schiff base macrocycles are reported, along with their anion binding properties as determined via UV-vis spectroscopic titrations carried out in dichloroethane. There is a striking difference between the interactions with anions of the two macrocycles, a finding ascribed to differences in their rigidity. For example, the more flexible dipyrromethane-derived macrocycle displays a 1.2:1 hydrogen sulfate versus nitrate selectivity, while its more rigid bipyrrole-derived congener shows a 7.4:1 selectivity in favor to hydrogen sulfate.
Sessler, J. L., Roznyatovskiy, V., Pantos, G. D., Borisova, NE., Reshetova, MD., Lynch, V. M., Khrustalev, V. N., & Ustynyuk, Y. A. (2005). Synthesis and anion binding properties of 2,5-diamidothiophene polypyrrole Schiff base macrocycles. Organic Letters, 7(23), 5277-5280. https://doi.org/10.1021/ol052162b