Gas-phase fragmentation of single atom incorporated Co5MS8(PEt3)6+ (M=Mn, Fe, Co, Ni) nanoclusters

Abstract

Functionalization of metal-chalcogenide clusters by either replacing one or more of the core metal atoms or by choosing the ligand is a powerful technique to tailor their properties and synthesize cluster assembled materials. Central to this approach is to understand the competition between the strength of the metal-ligand and metal-metal interactions within the cluster. We use collision-induced dissociation (CID) of two series of atomically precise metal sulfide nanoclusters including Co5MS8L6+ (L=PEt3, M= Mn, Fe, Co, Ni) and Co5-xFexS8L6+ (x=1-3) to understand the effect of a heteroatom incorporation on the core-ligand interactions and relative stability towards fragmentation. We observe sequential ligand loss as the dominant dissociation pathway for all the clusters, which occurs in competition with the loss of ligand sulfide (LS). Because all the ligands are attached to metal atoms in the precursor cluster cations, LS loss is an unusual dissociation pathway, indicative of a rearrangement of the cluster prior to fragmentation. Collision energy-resolved CID combined with theoretical calculations reveals the reduced stability of Co5MnS8L6+ and Co5FeS8L6+ cations towards the loss of the first ligand in comparison with their Co6S8L6+ and Co5NiS8L6+ counterparts. Moreover, we observe that the relative stability of clusters towards ligand loss as well as the competition between ligand and LS losses are strongly dependent on the composition of the clusters. Theoretical studies also confirm that the first ligand always prefers to detach from the doped-metal atom site to form Co5MS8L5+ cations. This study provides new insight into modulation of the core-ligand interaction of the atomically precise metal chalcogenide clusters suggesting paths to generate reactive species to promote inter-cluster reactions.