Growing community of artificial molecular machinists

Abstract

Over the past decades, chemists have been pursuing the creation of man-made molecular machines with either designed engineering-like operations or with higher performances compared with biological machines. The promise of creating an artificial molecular world traces its origins in the well-known lecture of Richard Feynman, There’s plenty of room at the bottom (1). Feynman’s insights into the immense possibilities of such small artificial machines, assembled in a straightforward manner, were deeply inspiring for the scientific community. The design of machines on the molecular scale is not an easy task to accomplish. Instead of gravity and inertia, which are omnipresent in the macroscopic world, random thermal fluctuations are prevalent and dominate movements on the molecular scale. Two main approaches are being considered for the construction of artificial molecular machines (AMMs): namely, bio-inspiration and miniaturization. The former consists of integrating concepts from naturally occurring machines and unnatural building blocks into AMMs, while the latter involves engineering nano-devices based on the mechanical actions of macroscopic machines. Perhaps a better way to design AMMs with unprecedented functions would be to follow neither of these routes, but rather to construct molecularly precise architectures based on recent advances in supramolecular chemistry: explore what has not been built by Nature. This unnatural route would only share with the biological world its fundamental laws at small scales, but differentiates it from its working processes. It is clear that the design of AMMs is a critical step in the process. It requires novel chemical building blocks to assemble and produce functioning systems. In this regard, mechanically interlocked molecules (MIMs) have paved the way for the synthesis of AMMs. MIMs, introduced by Jean-Pierre Sauvage (2) more than 30 years ago, signaled a breakthrough in introducing a new type of bond—the mechanical bond (3)—into chemistry. Examples of rotaxanes, catenanes, and other … [↵][1]1To whom correspondence should be addressed. Email: stoddart{at}northwestern.edu. [1]: #xref-corresp-1-1