How to Control the Rate of Heterogeneous Electron Transfer Across the Rim of M6L12 and M12L24 Nanospheres.

Catalysis in confined spaces, such as provided by supramolecular cages, is quickly gaining momentum. It al-lows for second coordination sphere strategies to control the selectivity and activity of transition metal cata-lysts, beyond the classical methods like fine-tuning the steric and electronic properties of the coordinating ligands. Only a few electrocatalytic reactions within cages have been reported, and there is no information regarding the electron transfer kinetics and thermodynamics of redox-active species encapsulated into supra-molecular assemblies. This contribution revolves around the preparation of M6L12 and larger M12L24 (M= Pd or Pt) nanospheres functionalized with different numbers of redox-active probes encapsulated within their cavi-ty, either in a covalent fashion via different types of linkers (flexible, rigid and conjugated or rigid and non-conjugated) or by supramolecular hydrogen bonding interactions. The redox-probes can be addressed by elec-trochemical electron transfer across the rim of nanospheres and the thermodynamics and kinetics of this pro-cess are described. Our study identifies that the linker type and the number of redox probes within the cage are useful handles to fine-tune the electron transfer rates, paving the way for the encapsulation of electro-active catalysts and electrocatalytic applications of such supramolecular assemblies.