π-Electronic systems responsive to metal ions and anions are very fascinating because they can form a variety of ion complexes as building subunits, providing supramolecular assemblies that exhibit attractive electronic and electrooptical properties.^[1]  In fact, anion complexes of pyrrole-based π-systems, such as dipyrrolyldiketone boron complexes and related molecules, have been found to construct ion-pairing assembled structures as solution-state aggregates, crystals, supramolecular gels, and thermotropic liquid crystals by combination with cationic species.  Derived from favorable overlap of charged π-planes, ion-pairing assemblies with the contribution of charge-segregated arrangements provided charge carrier mobilities, which are often larger than corresponding charge-by-charge-based assemblies, showing superior semi-conductive properties.  Recent achievements in arylethynyl-substituted derivatives include the formation of a variety of highly ordered structures, such as totally charge-segregated assemblies, based on [2+1]-type interlocked and [1+1]-type planar anion complexes.^[2]

1. A review: Maeda, H. Bull. Chem. Soc. Jpn. 2013, 86, 1359–1399.

2. Yamakado, R.; Sakurai, T.; Matsuda, W.; Seki, S.; Yasuda, N.; Akine, S.; Maeda, H. Chem. Eur. J. in press (DOI: 10.1002/chem.201503654).