Conjunction of Pyrrole and Amide Moieties: Highly Anion-Responsive π-Electronic Molecules Forming Ion-Free and Ion-Pairing Assemblies.

Dipyrrolyldiketone BF2 complexes with amide units at pyrrole α-positions were synthesized in modest yields and showed extremely high anion-binding affinities because of multiple hydrogen-bonding interactions. The phenyl-amide-substituted derivative formed solid-state chiral helical structures, wherein π planes were oriented parallel to the helical directions. Examination of anion-binding behavior using 1 H NMR spectroscopy combined with theoretical studies suggested fast pyrrole inversions, particularly for the phenyl-amide-substituted derivative. The anion complexes behaved as building units of ion-pairing assemblies in combination with planar and bulky cations.