Oxometalate and phosphine ligand co-protected silver nanoclusters: Ag28(dppb)6(MO4)4 and Ag32(dppb)12(MO4)4(NO3)4

Thiols, alkynyls and phosphines are the most widely used organic ligands to attain atomically precise metal nanoclusters, while oxometalates as inorganic ligands have almost been neglected in this field. Here, we used oxometalates (e.g., MoO42- and WO42-) as protecting ligands along with phosphines, such as 1,4-bis(diphenylphosphino)butane (dppb), to design and synthesize a new class of silver nanoclusters including Ag-28(dppb)(6)(MoO4)(4), Ag-28(dppb)(6)(WO4)(4) and Ag-32(dppb)(12)(MoO4)(4)(NO3)(4). Each cluster consists of a two-shell Ag-4@Ag-24 core protected by 4 oxometalates. These clusters exhibit similar optical absorption and photoluminescence properties that are not dependent on surface ligands. Furthermore, the electronic structure analysis shows that the clusters are 20-electron superatoms. This work demonstrates that oxometalates can play a key role in the formation of silver nanoclusters, and the effect of oxometalates should be considered in the design and synthesis of metal nanoclusters.