Quantum-sized gold nanoclusters: bridging the gap between organometallics and nanocrystals.

This Concept article provides an elementary discussion of a special class of large-sized gold compounds, so-called Au nanoclusters, which lies in between traditional organogold compounds (e.g., few-atom complexes, <1 nm) and face-centered cubic (fcc) crystalline Au nanoparticles (typically >2 nm). The discussion is focused on the relationship between them, including the evolution from the Au⋅⋅⋅Au aurophilic interaction in Au(I) complexes to the direct Au-Au bond in clusters, and the structural transformation from the fcc structure in nanocrystals to non-fcc structures in nanoclusters. Thiolate-protected Au(n)(SR)(m) nanoclusters are used as a paradigm system. Research on such nanoclusters has achieved considerable advances in recent years and is expected to flourish in the near future, which will bring about exciting progress in both fundamental scientific research and technological applications of nanoclusters of gold and other metals.