A Single Alkyne‐Induced Core Isomerism in AuCu Clusters and Its Impact on Electronic Structure and Photothermal Response

Ligands play a critical role in determining the geometric/electronic structures, and functional properties of metal clusters. While ligand exchange has emerged as a strategy for inducing structural and property modifications, the impact of exchanging a single ligand on the architecture and properties of metal clusters remains severely underestimated. In this study, we leverage Hard-Soft-Acid-Base (HSAB) principles to rationally govern controlled synthesis and directed transformation of bimetallic clusters. By employing a mixed-ligand system comprising bis(diphenylphosphino) methane (DPPM) and halogen (X), we first obtain a novel atomically precise cluster Au₁₆Cu₃X₅(DPPM)₆ (denoted as Au₁₆Cu₃-1). Subsequent partial substitution of a relative hard base (bromine) by a softer base (alkyne) yields another new cluster, Au₁₆Cu₃X₄(DPPM)₆(C≡CR)₁ (denoted as Au₁₆Cu₃-2. C≡CR represents deprotonated alkynes). Despite the minimal ligand exchange, comprehensive analyses reveal significant changes in the core structure and their electronic configuration. This subtle yet impactful modification leads to markedly altered excited-state dynamics and enhanced photothermal performance. By deciphering the interplay between ligand properties and core rearrangement, this study establishes a strategic framework for the rational design and transformation of bimetallic clusters, demonstrating how structural modulation directs their emergent optical and photothermal properties at atomic level.