Reversible isomerization of metal nanoclusters induced by intermolecular interaction

Summary Most inorganic nanoparticles are directly surface terminated (and stabilized) by protecting ligands, which could greatly affect the atomic packing and physical/chemical properties of their inorganic cores. Here, we show that the intermolecular interactions between the adsorbed molecules and surface ligands can also affect the core structure of inorganic nanoparticles. Through the coupling/decoupling of cationic surfactants (cetyltrimethylammonium cations, CTA+) and anionic surface ligands (para-mercaptobenzoic acid, p-MBA) in the aqueous phase, we have achieved a reversible transformation between two isomers of [Au25(p-MBA)18]− nanoclusters. The interconversion process between the two isomers shows the characteristics of a reversible nanocluster isomerization process. The two isomers are topologically connected via a simple rotation of the gold core without breaking any Au-S bonds at the metal-ligand interface. The adsorbed CTA+ cations would interact with the p-MBA layer through the CH∙∙∙π interaction and stabilize the more open ligand shell of the new isomer in the forward isomerization process.