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.