Precise control over molecular movement is of fundamental and practical importance in physics, biology, and chemistry. At nanoscale, the peculiar functioning principles and the synthesis of individual molecular actuators and machines has been the subject of intense investigations and debates over the past 60 years.
In this Chemical Review, Prof. Giuseppone and co-workers focus on the design of collective motions that are achieved by integrating, in space and time, several or many of these individual mechanical units together. In particular, they provide an in-depth look at the intermolecular couplings used to physically connect a number of artificial mechanically active molecular units such as photochromic molecular switches, nanomachines based on mechanical bonds, molecular rotors, and light-powered rotary motors. They highlight the various functioning principles that can lead to their collective motion at various length scales. They also emphasize how their synchronized, or desynchronized, mechanical behavior can lead to emerging functional properties and to their implementation into new active devices and materials.