A light-gated regulation of the reaction site by a cucurbit[7]uril macrocycle.

Competitive inhibition can be overcome by increasing the amount of catalyst in the reaction mixture. Here we present a pseudorotaxane system that circumvents this rule. A merocyanine inhibitor linked with the substrate obstructs the binding of the macrocyclic catalyst at the electrophilic reaction site preventing catalysis. Under UV light merocyanine is converted to the spiropyran form, losing its inhibition properties, thereby allowing the catalyst to bind the reaction center and promote the reaction. Moreover, when more than one nucleophile is present in the reaction mixture, the pseudorotaxane can scavenge a selected nucleophile and change the final product ratio. This work is a step forward in the development of new types of regulation in catalytic systems with remote control.