Electron-catalysed molecular recognition.

Molecular recognition 1-4 and supramolecular assembly 5-8 cover a broad spectrum 9-11 of non-covalently orchestrated phenomena between molecules. Catalysis 12 of such processes, however, unlike that for the formation of covalent bonds, is limited to approaches 13-16 that rely on sophisticated catalyst design. Here we establish a simple and versatile strategy to facilitate molecular recognition by extending electron catalysis 17 , which is widely applied 18-21 in synthetic covalent chemistry, into the realm of supramolecular non-covalent chemistry. As a proof of principle, we show that the formation of a trisradical complex 22 between a macrocyclic host and a dumbbell-shaped guest-a molecular recognition process that is kinetically forbidden under ambient conditions-can be accelerated substantially on the addition of catalytic amounts of a chemical electron source. It is, therefore, electrochemically possible to control 23 the molecular recognition temporally and produce a nearly arbitrary molar ratio between the substrates and complexes ranging between zero and the equilibrium value. Such kinetically stable supramolecular systems 24 are difficult to obtain precisely by other means. The use of the electron as a catalyst in molecular recognition will inspire chemists and biologists to explore strategies that can be used to fine-tune non-covalent events, control assembly at different length scales 25-27 and ultimately create new forms of complex matter 28-30 .