From “Dual-Cluster Coexistence” to One-Dimensional Chains: Anion-Regulated Assembly of Copper(I)-Iodide Supramolecular Clusters for Enhanced Photocatalysis

Abstract

The self-assembly of ionic copper(I) iodide clusters is hard to control due to the diverse Cu–I coordination modes. We propose an electrostatically driven strategy to direct distinct architectures within the same ligand system by simply varying the counteranion. A cavitand-like ligand based on a triphenylamine pyridinium salt was designed. Solvothermal assembly with Br– and PF6– anions afforded two anionic supramolecular clusters:Br– induced the formation of an anionic cluster (denoted HUBU-4, [(L1)3+2·(Cu6Br1.47I7.53)3–]·(Cu5Br0.66I7.34)3–) featuring a “dual cluster coexistence” motif, whereas PF6– directed the formation of a one-dimensional cluster chain (HUBU-5, [(L1·PF6–)2+·(Cu5I7)2–]∞). DFT calculations and photophysical/electrochemical measurements show that HUBU-5 has a narrower optical band gap, a smaller HOMO–LUMO gap, and stronger electronic transition capability than HUBU-4. (optical band gaps: 1.49 eV for HUBU-5 vs 1.62 eV for HUBU-4). Photocatalytic evaluation indicated that both clusters possess high activity for the copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) reaction under mild conditions, with a modest performance enhancement observed for the one-dimensional chain architecture. By simply changing the counteranion, this study achieves topological regulation of anionic copper(I) iodide clusters from 0D to 1D, revealing the structure-directing role of anions and offering an alternative design strategy for ionic supramolecular clusters.