Collection
2016 Nobel Prize in Chemistry
The 2016 Nobel Prize in Chemistry has been won by Jean-Pierre Sauvage, Fraser Stoddart and Ben Feringa, for their work on the design and synthesis of tiny molecular machines. This Collection, drawn from Nature Research journals, highlights some of the important contributions to this field.
Image credit: Nik Spencer / Nature
Review, news and comment
Thither supramolecular chemistry?
The way forward for a field in its infancy is to focus on complexity and integrated systems that may lead to emergent phenomena, suggests J. Fraser Stoddart at Northwestern University.
Microscopic reversibility as the organizing principle of molecular machines
Biological motors and pumps are equilibrium devices that couple chemical, electrical and mechanical processes in an environment that is far from equilibrium. Recognition of the key role played by microscopic reversibility in their operation is a first step towards rational design of artificial molecular devices.
The tiniest Lego: a tale of nanoscale motors, rotors, switches and pumps
Inspired by biology, chemists have created a cornucopia of molecular parts that act as switches, motors and ratchets. Now it is time to do something useful with them.
Molecular robot mimics life's protein-builder
Ribosome-inspired nanomachine links amino acids in pre-determined sequence.
Muscular molecules
Making muscle is easy, Philip Ball reports. All it takes is a molecular needle and thread.
No turning back for motorized molecules
A molecular motor has first to generate movements that are not swamped by Brownian motion, a dominant force at that scale, and cannot exploit angular momentum as a means of directional control. Despite these constraints, David Leigh and colleagues have developed a system that consumes a single chemical fuel to power a molecular machine that achieves continuous rotary motion as long as the fuel is present, and does not require any further chemical input or external stimulus. The motor consists of two interlocked molecular rings, the smaller of which (the macrocycle) is continuously transported directionally around the larger (the cyclic molecular track) when powered by irreversible reactions of a chemical fuel. Directionality is achieved via asymmetry in reaction rates of the chemical fuel added to the track, forcing the macrocycle to continue travelling in the same direction, rather than reversing towards the previous reactive point.
Running on information
An autonomous chemically driven artificial molecular machine uses information acquired by allosteric interactions combined with an exergonic reaction to know which way to go.
Two steps uphill
An axle-shaped molecule pumps charged rings from solution into an alkyl collection unit, a mechanism that, in two repetitive cycles, takes the system increasingly further from equilibrium.
A molecular production line
A small molecule that mimics the sequence-specific peptide synthesis of nature's ribosomes paves the way for more elaborate artificial molecular synthesizers.
Molecular machines muscle up
A supramolecular polymer made of thousands of bistable [c2]daisy chains amplifies individual nanometric displacements up to the micrometre-length scale, in a concerted process reminiscent of muscular cells.
Macromolecules flex their muscles
It will take a concerted effort for nanomachines to express themselves on a macroscopic scale. Could self-organizing helical polymers help?
Research
A 160-kilobit molecular electronic memory patterned at 1011 bits per square centimetre
The miniaturization of integrated circuits could stall in 20 years or so, when current technologies will scale down no further. Miniaturization beyond that point might be possible with DRAMs (dynamic random access memories, a concept derived from molecular electronics), the use of nanowires, and defect-tolerant architectures. Small, error-tolerant memory circuits combining these features have already been demonstrated, but this approach moves to another level with the development of a 160,000-bit molecular electronic memory, roughly analogous to a projected 'year 2020' DRAM circuit. The circuit still has large numbers of non-working memory bits, but they are readily identified and isolated; the working bits can then be configured as a fully functional random access memory. In a News Feature, Philip Ball looks at the computer architectures needed to exploit hyper-dense molecular memories.
Radically enhanced molecular recognition
The construction and operation of interlocked molecular machines often rely on the mutual recognition of different building blocks through a range of non-covalent interactions. Researchers have now shown that the versatility of bipyridinium systems can be increased by taking advantage of the complexes formed between their radical cations; with this approach they have been able to make electrochemically switchable bi- and tristable rotaxanes.
Reversing the direction in a light-driven rotary molecular motor
Biological rotary motors can alter their mechanical function by changing the direction of rotary motion. Now, researchers have designed a synthetic light-driven rotary motor in which the direction of rotation can be reversed on command by changing the chirality of the molecular motor through base-induced epimerization.
Electrically driven directional motion of a four-wheeled molecule on a metal surface
Any future artificial transporters and robots operating at the nanoscale are likely to require molecules capable of directional translational movement over a surface. Even the design of such molecules is a daunting task, however, as they need to be able to use light, chemical or electrical energy to modulate their interaction with the surface in a way that generates directional motion. Kudernac et al. now unveil just such a molecule, made by attaching four rotary motor units to a central axis. Inelastic electron tunnelling induces conformational changes in the rotors and propels the molecule across a copper surface. By changing the direction of the rotary motion of individual motor units, the self-propelling molecular 'four-wheeler' structure can follow random or preferentially linear trajectories. This design provides a starting point for the exploration of more sophisticated molecular mechanical systems, perhaps with complete control over their direction of motion.
Macroscopic contraction of a gel induced by the integrated motion of light-driven molecular motors
The coordinated motion of molecular rotors embedded in a gel network causes the material to contract on constant irradiation.
A molecular shuttle that operates inside a metal–organic framework
The piston-like, translational motion of a molecular shuttle — a process that is fundamental to many mechanically interlocked molecular switches and machines — has now been demonstrated to occur inside the highly organized and dense structure (containing approximately 1021 shuttles per cm3) of a metal–organic framework material.
Unidirectional rotary motion in achiral molecular motors
Avoiding equal probability for clockwise and anticlockwise rotation is essential for the function of molecular motors, and both biological and synthetic systems take advantage of chirality to control the rotary direction. Now it has been shown, by integrating two rotor moieties in a symmetric meso motor design, that light-driven unidirectional rotary motion can be achieved in an achiral system.
Tunable solid-state fluorescent materials for supramolecular encryption
Solid-state fluorescent materials show promise for potential applications in security and anti-counterfeiting technologies. Here, the authors report a heterorotaxane which has found application in security inks with highly tunable solid-state fluorescence through supramolecular encapsulation.
An artificial molecular pump
When supplied with redox energy, a dumbbell-shaped molecule can take small charged molecules from solution and thread them around an oligomethylene chain.
An autonomous chemically fuelled small-molecule motor
A molecular motor has first to generate movements that are not swamped by Brownian motion, a dominant force at that scale, and cannot exploit angular momentum as a means of directional control. Despite these constraints, David Leigh and colleagues have developed a system that consumes a single chemical fuel to power a molecular machine that achieves continuous rotary motion as long as the fuel is present, and does not require any further chemical input or external stimulus. The motor consists of two interlocked molecular rings, the smaller of which (the macrocycle) is continuously transported directionally around the larger (the cyclic molecular track) when powered by irreversible reactions of a chemical fuel. Directionality is achieved via asymmetry in reaction rates of the chemical fuel added to the track, forcing the macrocycle to continue travelling in the same direction, rather than reversing towards the previous reactive point.
A chemically powered unidirectional rotary molecular motor based on a palladium redox cycle
Control of motion at the molecular level is an integral requirement for the development of future nanoscale machinery. Now, governed by the fundamental reactivity principles of organometallic chemistry, a biaryl rotor is shown to exhibit 360° unidirectional rotary motion driven by the conversion of two simple fuels.
