A Molecular Lock

摘要

We introduce here the concept of a "molecular lock" exploiting the dual character of a platinum(Ⅱ)—pyridine (Pt-(Ⅱ)—Py) coordinate bond. This bond can be likened to a lock since it is irreversible ("locked") under ordinary conditions but becomes reversible ("released") in highly polar media at elevated temperature (Figure la). Incorporation of the molecular lock into a macrocyclic backbone made it possible to irreversibly interlock two molecular rings. Thus, molecular ring 1a involving the Pt(Ⅱ)—Py bond is on the lock in water and is not in equilibrium with other structures. However, once the lock is "released" by adding NaNO_3 and heating at 100℃, an equilibrium between 1a and its catenated dimer 2a arises, and the equilibrium is strongly pushed by polar media toward the catenane. After self-assembling in a high yield, catenane 2a is again locked up by cooling to room temperature and removing NaNO_3 (Scheme 1). This procedure completes molecular manipulation in which an organic architecture is built up molecule-by-molecule.