Ag₄₄(EBT)₂₆(TPP)₄ Nanoclusters With Tailored Molecular and Electronic Structure

Although atomically precise metalloid nanoclusters (NCs) of identical size with distinctly different molecular structures are highly desirable to understand the structural effects on the optical and photophysical properties, their synthesis remains highly challenging. Herein, we employed phosphine and thiol capping ligands featuring appropriate steric effects and synthesized a charge-neutral Ag NC with the formula Ag₄₄(EBT)₂₆(TPP)₄ (EBT: 2-ethylbenzenethiolate; TPP: triphenylphosphine). The single-crystal X-ray structure reveals that this NC has a hollow metal core of Ag₁₂@Ag₂₀ and a metal–ligand shell of Ag₁₂(EBT)₂₆(TPP)₄. The presence of mixed ligands and long V-shaped metal–ligand motifs on this NC has resulted in an enhancement of the NIR-II photoluminescence quantum yield by >25-fold compared to an all-thiolate-stabilized anionic [Ag₄₄(SR)₃₀]⁴⁻ NC (SR: thiolate). Time-dependent density-functional calculations show that our Ag₄₄ NC is an 18-electron superatom with a modulated electronic structure as compared to the [Ag₄₄(SR)₃₀]⁴⁻ anion, significantly influencing its optical properties.