Making and Operating Molecular Machines: A Multidisciplinary Challenge

Abstract

Movement is one of the central attributes of life, and a key feature in many technological processes. While artificial motion is typically provided by macroscopic engines powered by internal combustion or electrical energy, movement in living organisms is produced by machines and motors of molecular size that typically exploit the energy of chemical fuels at ambient temperature to generate forces and ultimately execute functions. The progress in several areas of chemistry, together with an improved understanding of biomolecular machines, has led to the development of a large variety of wholly synthetic molecular machines. These systems have the potential to bring about radical innovations in several areas of technology and medicine. In this Minireview, we discuss, with the help of a few examples, the multidisciplinary aspects of research on artificial molecular machines and highlight its translational character.

Photoactivated Artificial Molecular Machines that Can Perform Tasks

“…For the sake of the discussion and for space reasons, we limit our examination to systems that are instrumental for describing the examples reported in the next sections. In‐depth discussions on the mechanisms that enable controlled motion in molecular systems by exploiting an external energy source, and comprehensive reviews of photochemically driven synthetic molecular machines are available in the literature.…”

“…Molecular shuttles are rotaxanes in which the ring component can move in a linear fashion along a molecular axle endowed with terminal bulky groups to prevent dethreading . Systems of this kind, that are reminiscent of an abacus, are probably the most popular implementation of the molecular machine concept with artificial chemical species . The minimal design of a molecular shuttle in which the position of the ring along the axle can be controlled involves the incorporation of two different recognition sites (stations) on the axle.…”

“…During the past three decades, chemists have designed, synthesized, and investigated a large variety of molecular machines and motors based on the stimulation of appropriately designed molecular or supramolecular systems with chemical, electrical, or photonic inputs . Surely, the marriage of synthetic, physical, and analytical chemistry with an engineering mentality has led to ingenious achievements . More importantly, significant progress has been made in understanding controlled motion at the nanoscale, that is, how molecular‐sized objects can exploit an energy source to move directionally in an environment dominated by the incessant and random thermal agitation .…”

Light‐Responsive (Supra)Molecular Architectures: Recent Advances

“…The possibility of modulating the threading–dethreading kinetics of an interlocked ring–axle system by switching the corresponding energy barriers through an external stimulus has interesting implications in terms of controlling the architecture of a supramolecular system and modulating its physico‐chemical properties. Moreover, it is a starting point for the construction of rotaxane‐like species exhibiting relative unidirectional movements of the components, an important step forward in the development of artificial molecular motors …”

“…To enable the transition of artificial molecular devices from simple laboratory curiosities to key components of novel disruptive technologies, besides comprehending the fundamental principles and the processes by which molecular devices operate, a most daunting challenge has to be confronted: interfacing nanometer‐sized molecular objects with the macroscopic world, principally in relation to energy supply and information exchange. Indeed, molecular devices, similarly to their macroscopic analogues, require an energy source to operate and signaling pathways to communicate with the environment . Light is an ideal tool to fulfill both these requirements: light is able to “read” the state of a system, enabling the monitoring of its operations, because the photophysical properties of a system are usually strongly affected by the interactions between its components.…”