Emergent Self-Assembly of a Multicomponent Capsule via Iodine Capture

Described here is a three-component self-assembly system that displays emergent behavior that differs from that of its constituents. The system comprises an all-hydrocarbon octaaryl macrocycle cyclo[8](1,3-(4,6-dimethyl)benzene ( D 4d -CDMB-8 ), corannulene ( Cora ), and I 2 . No appreciable interaction is seen between any pair of these three-components, either in cyclohexane or under various crystallization conditions. On the other hand, when all three-components are mixed in cyclohexane and allowed to undergo crystallization, a supramolecular iodine-containing capsule, (( D 4d -CDMB-8 ) 3 ⊃ ( Cora ) 2 )⊃I 2, is obtained. This all-hydrocarbon capsule consists of three D 4d -CDMB-8 and two Cora subunits and contains a centrally bound I 2 molecule as inferred from single-crystal and powder X-ray diffraction studies as well as solid-state 13 C NMR and Raman spectroscopy. These analyses were complemented by solution-phase 1 H NMR and UV–vis spectroscopic studies. No evidence of I 2 escape from the capsule is seen, even at high temperatures (e.g., up to 418 K). The bound I 2 is likewise protected from reaction with alkali or standard reductants in aqueous solution (e.g., saturated NaOH(aq) or aqueous Na 2 S 2 O 3 ). It was also found that a mixed powder containing D 4d -CDMB-8 and Cora in a 3:2 molar ratio could capture saturated I 2 vapor or iodine from aqueous sources (e.g., 1.0 mM I 2 in NaCl (35 wt %) or I 2 + NaI(aq) (1.0 mM each)). The present system displays structural and functional features that go beyond what would be expected on the basis of a simple sum-of-the-components analysis. As such, it illustrates a new approach to creating self-assembled ensembles with emergent features.