Shifting the Paradigm: Acetylene Ligand in Unlocking Unique Cluster Nodes in Silver Cluster Assembled Materials and Its Photophysical Properties

Two-dimensional (2D) cluster-assembled materials are unique due to their exceptional optoelectronic and photoluminescence properties. The design and synthesis of 2D materials, where clusters serve as nodes interconnected by conjugated linkers, could significantly enhance the coupling between the nodes, thereby facilitating efficient charge transfer. We have synthesized a novel 2D alkynyl-ligand protected cluster assembled material (CAM) consisting of two distinct types of Ag₁₄ nodes, which are interconnected by pyrazine molecules to form the overall architecture. The presence of two different geometries within the same CAM structure is a rare observation. The formation of this structure could be attributed to the specific bonding interaction between the acetylene ligand and the silver ions. Combined experimental and theoretical calculations revealed that electronic excitation is primarily driven by mixed transition characters. These include π → π* transitions, where electron transfer occurs from occupied C-p orbitals to the vacant π* orbitals of the alkynyl carbon or pyridyl nitrogen atoms, as well as LMCT (Ligand-to-Metal Charge Transfer) transitions mixed with cluster-centred states.