Synthesis, Structure, and Dynamic Behavior of Discrete Metallacyclic Rotors

Molecular rotors are a type of molecular machine that can rotate with respect to its surrounding environment or in which one part rotates with respect to another part. Various approaches to preparing rotary molecular motors with variable radii and functional groups have been attempted because rotating units are ubiquitous in natural systems. The motion of these rotors in solution or on a solid surface can be monitored either by NMR or STM techniques. Previous findings indicate that the motion of a molecular rotor can be manipulated in a more controlled fashion by changing the molecular structure or applying external stimuli such as heat, photons, electricity, chemical reactions, or applying external field STM tunneling current. Molecular dynamics simulations have also been performed in attempts to understand the molecular rotations of rotors, and the theoretical calculations agree well with experimental observations. In this highlight review, we describe synthetic approaches, structural characterization, and dynamic behavior of discrete metallacyclic rotors in solution and on solid surfaces.