When two or more cationic units can be stacked, they can show novel properties and functions, which can be switched by an external stimulus, such as an electric potential. However, under dispersed conditions, such as in solution, cation units cannot be stacked effectively to interact with each other, due to Coulombic repulsion and/or entropical disadvantage. Therefore, there are very few successful examples of realizing the proximity of cationic species, when compared to the results with neutral molecules. Moreover, the redox behavior of stacked cations has not yet been well studied, and thus there is still room to explore novel properties of stacked multi-cationic species.