Charged porphyrins: χ-electronic systems that form ion-pairing assembled structures

Abstract

Noncovalent interactions are important for determining the assembling modes of materials. Electronically neutral π-systems form stacking structures based on ππ interactions, which are mainly derived from dispersion forces. Introducing charges into π-systems would affect the interaction, owing to the increased contribution from electrostatic forces. This unique interaction, which we have proposed as iπiπ interaction, can provide ion pairs that form assembled structures. The number of possible combinations of ion pairs can be obtained as the product of the number of components being paired. As π-electronic ions, especially anions, are more reactive than electronically neutral π-systems, their stabilization is required. We have recently focused on porphyrins as platforms to stabilize π-electronic ions by charge delocalization over their large π-systems. In addition, the facile structural modifications of porphyrins enable tuning of the assembly modes and functionalization of the ion-pairing assemblies. In this account, progress of charged porphyrin derivatives and their ion-pairing assembly behaviors is summarized.