Merging Nanoparticle and Capsule Single Electron Transfer Catalysis

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Nature frequently uses radical processes in biosynthesis. While various co-factors are employed to initiate single electron transfer (SET), the protein framework plays a quite different role to conventional ionic enzyme mechanisms - controlling inherently reactive species rather than activating normally stable entities. Recently, the Lusby group uncovered a novel approach to host-guest chemistry wherein an inherently polarised Pd2L4 cage structure encapsulates guests using multiple weak H-bonds. We have also found that binding "activates" weakly-oxidising quinones, such as chloranil, so that they catalyse various SET-based reactions ([4+2], [2+2] cycloadditions etc.) not observed for the unbound quinones.This project presents several challenges and opportunities. Metal nanoparticles have not previously been functionalised with coordination assemblies, therefore issues such as controlling surface coverage of multitopic ligands will likely be key to success. However, the surface modification methodology developed by Kay will facilitate this ambitious exploratory science.4 We also anticipate that the capsule microenvironment can be tuned to affect both forward and reverse SET and hence reactivity, while the confines will also play a key role in controlling regio and/or diastreoselectivity.