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Issue 18, 2017
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Mastering the non-equilibrium assembly and operation of molecular machines

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Abstract

In mechanically interlocked compounds, such as rotaxanes and catenanes, the molecules are held together by mechanical rather than chemical bonds. These compounds can be engineered to have several well-defined mechanical states by incorporating recognition sites between the different components. The rates of the transitions between the recognition sites can be controlled by introducing steric “speed bumps” or electrostatically switchable gates. A mechanism for the absorption of energy can also be included by adding photoactive, catalytically active, or redox-active recognition sites, or even charges and dipoles. At equilibrium, these Mechanically Interlocked Molecules (MIMs) undergo thermally activated transitions continuously between their different mechanical states where every transition is as likely as its microscopic reverse. External energy, for example, light, external modulation of the chemical and/or physical environment or catalysis of an exergonic reaction, drives the system away from equilibrium. The absorption of energy from these processes can be used to favour some, and suppress other, transitions so that completion of a mechanical cycle in a direction in which work is done on the environment – the requisite of a molecular machine – is more likely than completion in a direction in which work is absorbed from the environment. In this Tutorial Review, we discuss the different design principles by which molecular machines can be engineered to use different sources of energy to carry out self-organization and the performance of work in their environments.

Graphical abstract: Mastering the non-equilibrium assembly and operation of molecular machines

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Publication details

The article was received on 27 Jan 2017 and first published on 24 Mar 2017


Article type: Tutorial Review
DOI: 10.1039/C7CS00068E
Citation: Chem. Soc. Rev., 2017,46, 5491-5507
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    Mastering the non-equilibrium assembly and operation of molecular machines

    C. Pezzato, C. Cheng, J. F. Stoddart and R. D. Astumian, Chem. Soc. Rev., 2017, 46, 5491
    DOI: 10.1039/C7CS00068E

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