Modular supramolecular dimerization of optically tunable extended aryl viologens.

Abstract

Cucurbit[8]uril (CB[8]) mediated assembly of extended aryl viologens (EVs) into optically-tunable dimers is reported for the first time. We show that modular design and synthesis of a new class of -conjugated viologen derivatives with rigid aromatic or heteroaromatic bridging units as well as electron donating molecular recognition motifs enables their self-assembly into 2:2 complexes with CB[8]. The quantitative dimerization process involving these two molecular components in an aqueous solution enables excimer-like interactions between closely packed charged guests giving rise to distinct spectroscopic behavior. The nature of these dimers (CB[8]2 · (EV[X]R)2) in the ground and excited states were characterized by NMR, isothermal titration calorimetry, and steady-state spectroscopic measurements.