Fine tuning the anion binding properties of 2,6-diamidopyridine dipyrromethane hybrid macrocycles

The synthesis, characterization, and anion-binding properties of a series of 2,6-diamidopyridine dipyrromethane hybrid macrocycles is presented. As part of this work, a new method for effecting the oxidation of dipyrromethane-based macrocycles in organic solvents has been developed. The macrocyclic frameworks presented here stand out because of their ease of synthesis and tunable anion-binding properties. Evidence for anion binding was obtained from UV-vis spectroscopic titrations carried out in acetonitrile. The results clearly indicate that by changing the flexibility, cavity size, and directionality of anion-binding moieties in the macrocyclic framework the anion selectivity may be changed dramatically. These results are in accord with density functional theory molecular modeling calculations performed on one member of the series.