Programmed Assembly of IrAu₁₂ Nanoclusters into Dimers and Trimers: Electron Microscopy Observation and Spectroscopic Characterization.

Abstract

Ligand-protected gold nanoclusters have attracted attention as building blocks for functional materials. In this study, we have demonstrated the programmed assembly of the icosahedral Ir@Au₁₂ nanoclusters into a dimer, a linear trimer, linear oligomers, or a triangular trimer via the reaction between IrAu₁₂ with predefined binding sites and bi- or tridentate isocyanide linkers. The formation of the intended structures was confirmed by high-angle annular dark-field scanning transmission electron microscopy using a newly developed sampling protocol. Statistical analysis of the interparticle distances provided quantitative structure models consistent with the theoretically predicted structures. The linear oligomers exhibited a new absorption peak at ∼480 nm. Theoretical calculations indicated that the electron transfers from the IrAu₁₂ moiety to the linker ligand or another IrAu₁₂ moiety involve the absorption. This study demonstrates that programmed assemblies of Au nanoclusters will provide an opportunity to elucidate how novel collective properties arise through assembly.