Stoichiometry-Driven Polymorphism of (Au3Pz3)2Ag Sandwich Clusters Enables Packing-Controlled Photoluminescence

Area of Science:

• Materials Science
• Inorganic Chemistry
• Photophysics

Background:

• Controlling photophysical properties of metal clusters is challenging due to coupled structure and packing.
• Altering intrinsic metal cores often changes desired properties.

Purpose of the Study:

• To demonstrate packing-controlled photoluminescence in metal clusters without altering the core.
• To utilize a gold (I) complex (Au3) as a precursor for hierarchical assembly.

Main Methods:

• Synthesized two polymorphs (Au6Ag-α and Au6Ag-β) by varying feed ratios of Au3 and AgBF4.
• Characterized structures using single-crystal X-ray diffraction.
• Performed theoretical calculations to understand electronic properties and packing effects.

Main Results:

• Obtained two polymorphs with identical composition but distinct photoluminescence (yellow vs. red-shifted orange).
• Au6Ag-β exhibited higher quantum yield due to tighter packing and intersandwich interactions.
• Identified ligand-to-metal-metal charge transfer (LMMCT) as key to emission differences.

Conclusions:

• A structurally defined cluster precursor enables spatial packing control over compositionally identical clusters.
• This approach allows tuning of photophysical properties without modifying the intrinsic metal core.
• Offers a viable strategy for designing advanced luminescent materials.