Anionic Supramolecular Cluster with [Cu₄Br₇O]^2- Core: Self-Assembly and Photocatalysis for Organic Transformations

The design and development of photoactive cuprous halide cluster catalysts have attracted considerable attention in photocatalysis. Herein, we report the rational design of a cationic tripodal ligand (L¹·3PF₆^-)-bearing luminescent organic groups. The reaction of ligand L¹ with cuprous bromide directs the assembly of a highly stable polynuclear supramolecular cluster centered on a tetrahedral [Cu₄Br₇O]^2- core. The coordination geometry of Cu(I) and Br^- is precisely controlled through synergistic metal coordination and electrostatic interactions, while C-H···Br hydrogen bonds and π-π stacking further stabilize the architecture. The tripodal ligands self-assemble into hydrogen-bonded dimeric capsules that encapsulate the anionic clusters and organize them into a two-dimensional framework through a synergistic electrostatic stabilization. The resulting anionic copper-based supramolecular cluster shows strong photoexcitation and oxidative activity, enabling efficient photocatalysis for organic transformations. Under 455 nm irradiation, the cluster exhibits dual photocatalytic activity, achieving near-quantitative yields for both arylboronic acid hydroxylation and benzylamine oxidative coupling with excellent stability over three cycles. Mechanistic studies identified the key reactive oxygen species and clarified distinct photocatalytic pathways. This work advances the synthesis of polynuclear [Cu₄Br₇O]^2- assemblies and demonstrates their utility as copper bromide photocatalysts for diverse organic transformations.