Azobenzene is a remarkable molecule.

In the dark, at equilibrium, azobenzene is >99% trans. Irradiation at 340 nm leads to the production of up to ~90% of the cis isomer. Irradiation at longer wavelengths and/or thermal relaxation returns the trans isomer. Cis and trans isomers of azobenzene differ significantly in structure and dipole moment. We have used each of these differences to control biomolecular structure and activity.


The trans (top) and cis (bottom) forms of azobenzene.

Current work

New azobenzene-based photoswitches.

We recently found that substituton of all four ortho positions with methoxy groups (synthetic scheme below) leads to a separation of the n-pi* transition wavelengths for cis and trans isomers (see J. Am. Chem. Soc, 2011, 133 (49), pp 19684–19687). This permits effective photoswicthing without using UV light - a big plus for biological applications.

Current work is aimed at designing derivatives with even longer switching wavelengths and derivatives that work together with different colours of light.

We are also trying to maximize the conformational effect on attached peptides and proteins by making longer, rigid derivatives.