Photoisomerization of Azobenzene

trans-Azobenzene → cis-Azobenzene

Overview

UV light (340 nm) converts the thermodynamically stable trans isomer of azobenzene to the cis form through rotation around the N=N bond. Visible light (450 nm) or thermal relaxation converts it back. The large geometric change (9 Å to 5.5 Å end-to-end distance) makes azobenzene a versatile molecular switch.

Everyday Example

Azobenzene-based molecular motors can move objects millions of times their own mass when triggered by light.

Industrial Importance

Azobenzene photoswitches are used in molecular machines, drug delivery systems, liquid crystal displays, and data storage research.

Properties

Type: Photochemical
Reversible: Yes
Energy: Endothermic
ΔH: 50.0 kJ/mol

Related Reactions

Chlorophyll Fluorescence Cis-Trans Isomerization of Retinal Dye-Sensitized Solar Cell (Grätzel Cell) Firefly Bioluminescence (Luciferin Oxidation) Luminol Chemiluminescence Ozone Decomposition by UV Ozone Formation by UV Light Photocatalytic NOx Removal Photocatalytic Water Splitting (TiO₂) Photochemical Cycloaddition ([2+2])

Frequently Asked Questions

What is the equation for Photoisomerization of Azobenzene?

The balanced equation is: trans-Azobenzene → cis-Azobenzene.

What type of reaction is Photoisomerization of Azobenzene?

Photoisomerization of Azobenzene is a photochemical reaction. It is reversible under certain conditions.

Is Photoisomerization of Azobenzene exothermic or endothermic?

Photoisomerization of Azobenzene is endothermic (absorbs energy). The enthalpy change (ΔH) is 50.0 kJ/mol.