Construction of Multiply Bridged Coordination Framework via a Cluster-Ligand Strategy.

Abstract

In the context of reticular chemistry, linking secondary building units (SBUs) through multiple bridging modes could enhance structural robustness and facilitate the development of versatile frameworks. However, the deliberate synthesis of coordination frameworks by these multiply bridged SBUs remains challenging, as the component SBUs are typically generated in situ during framework assembly. Here, we report facile synthesis of a multiply bridged coordination framework via a cluster-ligand strategy, where pre-functionalized metal nanoclusters (NCs) with high-density coordination sites are used as multi-bridging linkers to transition metal cluster nodes. Specifically, a predesigned [Au₂₅(p-MBA)₁₈]^-1 (p-MBA = p-mercaptobenzoic acid) NC, featuring peripherally decorated 18 carboxyl groups in a self-adjustable and environmentally adaptive configuration, functions as both SBUs and highly coordinated linkers. This highly coordinated [Au₂₅(p-MBA)₁₈]^-1 assembles into a (4,8)-connected rhombic dodecahedral framework (Au₂₅-Zn₅) through doubly and triply bridging to Zn₅ clusters. The ordered co-assembly enhances the near-infrared (NIR) emission of [Au₂₅(p-MBA)₁₈]^-1 and yields supercrystals suitable for x-ray crystallography analysis, providing a good means to resolve the structural and luminescence enhancement mechanism of water-soluble metal NCs. Leveraging the enhanced NIR emission and improved structural stability assured by the multiple bridging modes, Au₂₅-Zn₅ could serve as a versatile and leak-free NIR-emissive coating for real-time image-guided tumor surgery.