Stimuli-Responsive Folding and Unfolding of a Polymer Bearing Multiple Cerium(IV) Bis(porphyrinate) Joints: Mechano-imitation of the Action of a Folding Ruler

摘要

The design of molecular machines, in which the properties and functions are controlled by photo-, redox-, and host-guest-type interactions, has attracted growing attention.'1 Interest has been focused on synthetic actuating molecules that exhibit contraction/expansion motion, because a typical biological molecular machine, myosin, can directly convert chemical energy derived from ATP hydrolysis into mechanical motion with extremely high efficiency. In a synthetic system, it has been recently demonstrated that a sliding motion, a spring-like motion, and a conformational change of synthetic molecules induce the contraction/ expansion of their structures triggered by external stimuli. Challenges still remain in the design and synthesis of a new molecule toward organic mechano-responsive materials that deliberately undergo structural changes in length. It occurred to us that the rational combination of a pivoting motion, like a "folding ruler", and a stimuli responsive moiety enables us to construct a new class of actuating molecules.