molecular switch (rus. молекулярный переключатель) — a molecule that may exist in two or more stable states. The molecule may be reversibly shifted between the states in response to external effects, such as heat, light, change in pH, exposure to chemicals, magnetic or electrical fields.

Description

A shift between the states of a molecular switch implies an abrupt change in its properties, including geometric, electronic, optical, electric and other properties. The best example of a molecular switch is a pH indicator that reversibly changes colour in response to changing the pH of a medium. Photochromic indicators involve a reversible photochemical reaction, such as cis-trans isomerisation or cycle opening/closure (Fig. 1). Many of these reactions may occur in response to heating: for example, molecules containing azobenzene as one of their fragments may rapidly change shape when heated (Fig. 2). Any change in the properties of a molecular switch under the influence of external effects is marked by an optical, electric, biological, etc. signal. Due to this effect, molecular switches may be used as components of nanoelectronics devices.

Illustrations

Fig. 1. Reversible opening and closing of cycle in a photochromic molecular switch [3].
Fig. 1. Reversible opening and closing of cycle in a photochromic molecular switch [3].
Fig. 2. Cis-trans isomerization of azobenzene exposed to heating and light.
Fig. 2. Cis-trans isomerization of azobenzene exposed to heating and light.

Author

  • Eremin Vadim V.

Sources

  1. J-M Lehn. Supramolecular Chemistry. Concepts and Perspectives . — Wiley-VCH, 1995. - 271 p.
  2. J. W. Steed and J. L. Atwood, "Supramolecular Chemistry", 2nd Ed, J. Wiley & Sons: Chichester, 2009. - 990 p.
  3. Fraysse S., Coudret C., Launay J.-P. // Eur. J. Inorg. Chem. 2001. V. 7. P. 1581–1590.

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