On the Size Evolution of Monolayer-Protected Gold Clusters during Ligand Place-Exchange Reactions: The Effect of Solvents

Ligand place‐exchange (LPE) reactions are extensively applied for the post‐functionalization of monolayer‐protected gold clusters (MPCs) by using excessive incoming ligands to displace initial ones. However, the modified MPCs are often enlarged or degraded; this results in ill‐defined size‐dependent properties. The growth of MPCs essentially involves an unprotected surface that is subsequently has gold atoms added or is fused with other gold cores owing to collision. Reported herein is a guideline for the selection of solvents to suppress unwanted MPC growth. Favorable solvents are those with significant affinity to gold or with low solubility for desorbed ligands because these properties retard LPE reactions and minimize the time available for unprotected gold cores. This finding provides a general and convenient approach to regulate the size of functionalized MPCs. Do not grow up, please! The size of gold clusters is important in their photophysical and electrical properties. To increase processability and applications, the displacement of initial ligands by those desired is a common approach; however, this generally accompanies a growth in the clusters. A facile method that allows modification, while maintaining the cluster sizes, is described (see picture).