Practical Stability of Au25(SR)18-1/0/+1.

Superatom electron shell and/or geometric shell filling underlies the thermodynamic stability of coinage and alkali metal clusters in both theoretical and experimental results. Factors beyond simple shell filling contribute substantially to the lifetime of ligated clusters in solution. Such factors include the nature of the solvent, the atmosphere and the steric size of the ligand shell. Here we systematically lay out a 'practical' stability model for ligated metal clusters, which includes both shell-closing aspects and colloidal stability aspects. Cluster decomposition may follow either fusion or fission pathways. Solvent polarity can be determinative of the decomposition pathway.