Photoswitchable Thioureas for the External Manipulation of Catalytic Activity

A series
of azobenzene-based thiourea catalysts have been developed
with the aim of achieving control over the catalytic activity by the
use of light. The conceptual design of these systems relies on the
inactivation by means of intramolecular hydrogen bonding, only likely
to take place in one of their isomeric forms. After fine structure
modulation of the catalyst a substantial difference in activity has
been observed between the irradiated and the nonirradiated reaction.
Furthermore, the system allowed in situ manipulation of the catalyst
activity during the course of a given experiment.