Dimension-controlled ion-pairing assemblies based on π-electronic charged species

This feature article summarizes the recent progress in the study of ion-pairing assemblies based on π-electronic ion pairs, including anion complexes of π-electronic molecules. Recently, ionic self-assembly (or ion-pairing assembly) has been widely investigated and utilized in the fabrication of various functional materials including soft materials, surface morphologies and organic-inorganic hybrid materials. It is significantly important to precisely design and synthesize charged π-electronic systems for obtaining highly organized assemblies, but the development of π-electronic ion pairs with an aim to fabricate soft materials has hardly been examined. This is because in many cases it is difficult to arrange the desired charged species due to their synthetic difficulties. In view of this scenario, tailor-made π-electronic ion pairs consisting of ion complexes of π-electronic molecules and their counterions can be used as the building blocks for ion-pairing assemblies. In particular, dimension-controlled ion-pairing assemblies can be formed based on π-electronic charged species, which have potential for use as functional nanostructured materials. In this feature article, we overview the basic synthetic strategies and recent examples of ion-pairing assemblies comprising π-electronic systems.