Specially designed sulphonium salt labels can be used as electron acceptors for radical formation in photoactive electron donor-acceptor complexes, where you do not need metal catalysts, write British researchers in Nature Chemistry.

Radicals in organic chemistry are reactive compounds that can engage in unusual reactions. But to form a radical compound, you need to separate the electrons of a bond, and that’s the tricky part. An up-and-coming option is the photoactivation of electron donor-acceptor (EDA) complexes. As the name suggests, this works with an electron donor and an electron acceptor forming a complex. If you then shine (visible) light on the complex, a single-electron transfer (SET) takes place, which results in two radicals.

It works with aromatic compounds (also called arenes), but only if you attach the right functional groups. As such, you have little creative freedom and are limited by the electronic properties of the aromatic precursors. British researchers at the University of Manchester led by David Procter thought that was too inefficient. So they designed a