Assembly of anionic silver nanoclusters with controlled packing structures through site-specific ionic bridges

Abstract

The assembly of metal nanoclusters (NCs) into crystalline lattice structures is of interest in the development of NC-based functional materials. Here we demonstrate that the assembled structures of tri-anionic tetrahedral symmetric [Ag₂₉(BDT)₁₂]³⁻ (Ag₂₉ NC, BDT: 1,3-benzenedithiol) NCs are controlled into a polyethylene-like zigzag chain and a “poly-ring-fused-cyclohexane”-like honeycomb arrangement through ionic interactions with alkali metal cations such as K⁺ and Cs⁺. The site-specific binding of alkali metal ions on the tetrahedrally arranged binding sites of Ag₂₉ NCs successfully connects the adjacent NCs into various packing modes. The number and type of bridges between NCs determine the Ag₂₉ NC packing structures, which are affected by the solvent species, enabling the transformation of packing modes in the single-crystalline state. The photoluminescence (PL) properties of the crystals responded to the packing modes of the NCs in terms of anisotropy and bridge linkage style inducing a varied degree of relaxation of the excited state depending on the relocation mobility of alkali metal ions in the crystals.