Thiolate-protected gold clusters are of continuously growing fundamental and applied interests. These molecular systems can be defined as soft-hardmolecules, i.e., molecules in which a hard gold core is protected by a soft interface of flexible ligands that form a quite unique nanoenvironment. A typical example is provided by Au25(SR)18, which is the most studied of the nanoclusters displaying molecular properties. In applications, assessing the dynamic behavior of the thiolate monolayer is crucial as it determines, e.g., the cluster's effective size and electron-transfer (ET) properties. Topics addressed in this talk will include: (i) The effect of the monolayer thickness and its dynamics on the ET between molecular nanoclusters in films and solution; (ii) In redox catalysis, the monolayer can be penetrated by molecular species: what kind of environment do they experience during the activation processes? (iii) Understanding the fine interactions between the cluster metal core and the thiolate monolayer is especially important because the latter interfaces the former to the surrounding medium: nuclear and electron magnetic methods can be used to understand orbital distribution outside the metal core; (iv) Ligand exchange in clusters and interactions between the ligands of two clusters are instrumental to modify the cluster monolayer, cause polymerization in the solid state, and make two clusters fuse to form different clusters; (v) Techniques such as nuclear magnetic resonance and electrochemistry are especially valuable to assess the thiolate-protected cluster structure in solution.
