Synthesis and Anion Binding Properties of 2,5-Diamidothiophene Polypyrrole Schiff Base Macrocycles

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.