Designed Self-Assembly of Molecular Necklaces Using Host-Stabilized Charge-Transfer Interactions

A novel approach to the noncovalent synthesis of molecular necklaces successfully led to the first quantitative self-assembly of a molecular necklace 6MN, in which five small rings are threaded on a large ring, from 10 components. Our strategy involves the host-guest complex formation between the molecular host cucurbit8uril (CB8) and a guest molecule in which an electron donor and an electron acceptor unit are connected by a rigid linker with a proper angle, to form a cyclic oligomer through the host-stabilized intermolecular charge-transfer (CT) complex formation. In the structure of the molecular necklace 6MN, five molecules of the guest form a cyclic framework by the intermolecular CT interactions, on which five CB8 molecules are threaded with an arrangement reminiscent of a five-fold propeller. The molecular necklace measures approximately 3.7 nm in diameter and approximately 1.8 nm in thickness.