Stimuli-responsive dynamic pseudorotaxane crystals

Abstract

This review summarizes recent advances in stimuli-responsive dynamic molecular crystals. For the construction of dynamic molecular crystals with response to external stimuli, such as light and/or heat, a number of strategies are available, which are based on (i) metal–organic frameworks, (ii) molecular rotors, (iii) photochromic molecules including azobenzenes and diarylethenes, (iv) cycloaddition reactions, and (v) rotaxanes and pseudorotaxanes. In particular, this review focuses on our recent results on dynamic pseudorotaxane crystals. Pseudorotaxane molecules comprising a crown ether as a ring and an ammonium cation as an axle respond to light and/or heat changing their molecular structures in the single-crystal state. Such structural changes at a molecular level influence the macroscopic properties of pseudorotaxanes, including mechanical motions of the crystals. Consequently, they are potential candidates for application as light-sensing and harvesting materials in microdevices for photomechanical conversion.