Interplay of Photoisomerization and Phase Transition Events Provide a Working Supramolecular Motor

Abstract

Autonomous molecular-based microrobots have not been created despite progress in our understanding of the chemistry of molecular motors and machines. In the field of chemistry, the design and synthesis of molecular structures remain an ongoing and diverse challenge. The creation of a system in which molecular structures interact represents an additional challenge. In order to functionalize a molecule for a motor, it must be exposed to a specific reaction field. Synchronization of the molecules involved is also required. In this chapter, we discuss our research results on self-oscillatory flipping motions of azobenzene-containing assemblies. Briefly, reversible photoisomerization of an azobenzene derivative occurs under steady light irradiation. In coordination with phase transition events, a cycle modulated by the components involved leads to repetitive structural changes. When this azobenzenebased assembly is placed in water, the assembly exhibits autonomous swimming. This macroscopic light-powered motion is the result of the self-organization of a large number of nanometer-scale molecules and it provides an example of the potential for mechanical work to be performed by molecular assemblies.We subsequently describe the driving concept of far-from-equilibrium dynamics, namely a dissipative structure by which a spatial pattern maintains dynamic behavior to drive the mechanical motion observed.