Helical Aggregates of Building Blocks Formed In Situ from Five Components

Reported here is the induced helical aggregation of an achiral cationic perylene-3,4-dicarboximide (1) that contains a phenylboronic acid group, together with UMP that bears a cis-diol moiety able to interact with boronic acid and an imide group known to coordinate with Hg2+. In selected solvents, 1 exists in monomer form, even in the presence of either UMP or Hg2+. Helical aggregation only takes place if 1 is mixed with both UMP and Hg2+, which is shown to result from the formation of a building block consisting of five components in the form 1-U- Hg2+-U-1. Strong exciton-coupled circular dichroism signals were observed in the absorption window of the achiral dye chromophore, demonstrating the transfer of the chirality of UMP to the supramolecular aggregates of P-helicity. Synergism was shown to occur upon aggregation of the 1-U-Hg2+-U-1 building block, as substantially enhanced affinity and binding selectivity were observed for UMP and Hg2+, despite the otherwise weak and less selective interactions of 1-UMP and UMP-Hg2+. In support of this synergism, the g-factor of the aggregates was found to be 1.4 V 10(-2), which represents a high value. We thus show a strategy of in situ construction of a building block from multiple components, among which the interactions can be weak and less selective. Therefore, the design and syntheses of the constituent components are substantially simplified, yet diverse functions can be expected from their supramolecular aggregates.