Question

1. What are two examples of ‘molecular switches’ from our current material? What acts as the ‘switch’ in each case?

Answer 1

Molecular Switches are the molecular devices that consist of a single molecule which can shift controllably between two stable states. The trigger that helps in the switch between the states are electrical current, temperature or chemical or light.

Examples -

1. Acidochromic molecular switches
2. Photochromic Switches
3. Spiropyrans
4. Nanoparticles.

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A. Acidochromic molecular switches

They are found in plants like roses, cornflowers, primroses and violets. These compound are used as pH indicators. After the addition of acid or a base, the equilibrium between the two forms will be displaced.

2. Photochromic Switches

They are the molecule that can optically be switched between two isomers and has a difference in optical properties.

Example - Tuned laser light
It acts as a switch which selectively transforms the molecule from one isomer to the other leading to changes its absorption wavelength, luminescence and optical rotation.

3. Nanoparticle Switches

Example - bistable gallium nanoparticles.

4. Spiropyrans
Spiropyrans act as isomerization between a closed spiropyran and open merocyanine that can be induced by light,

Whilst there is a large range of photochromic compounds available, their properties must be selected carefully to ensure good performance as switches.