Understanding and designing one-dimensional assemblies of ligand-protected metal nanoclusters†
If we wish to use metal clusters as magnetic materials and dipole materials, it is necessary to assemble the clusters to attain a certain material size. However, the types of building-block clusters suitable for assembly are currently very limited, and thereby we have little information on the factors required to assemble metal clusters and the physical properties and functions of such assembled structures. In this research, we found the following four points about thiolate (SR)-protected gold–platinum alloy (Au4Pt2) clusters ([Au4Pt2(SR)8]0); (1) [Au4Pt2(SR)8]0 is a metal cluster that can be used as a building block to form one-dimensional (1D) connected structures (1D-CS) via inter-cluster Au–Au bonds (aurophilic bond); (2) although all [Au4Pt2(SR)8]0 clusters have similar structures, the intra-cluster ligand interactions vary depending on the ligand structure. As a result, the distribution of the ligands in [Au4Pt2(SR)8]0 changes depending on the ligand structure; (3) the differences in the distributions of the ligands influence the inter-cluster ligand interactions, which in turn affects the formation of 1D-CS and changes the connected structure; and (4) the formation of 1D-CS decreases the band gap of the clusters. These results demonstrate that we need to design intra-cluster ligand interactions to produce 1D-CS with desired connecting structures.