In this work, we illustrated a novel design strategy that allows systematically tunable interior properties (effective cavity size, steric crowdedness, and hydrophobicity) contained within a novel class of shape-persistent aromatic pentamers to take place on a scale below 3 A. Such finely tunable structural features are complimented by experimentally observable functional variations in ion-binding potential. Results of the selective, differential binding affinities of three circular pentamers for Li(+), Na(+), K(+), Rb(+), and Cs(+), substantiated by metal-containing crystal structures and computational modeling, are detailed.