Interfacial magnetism in a fused superatomic cluster [Co6Se8(PEt3)5]2

Abstract

An isolated Co₆Se₈(PEt₃)₆ cluster is non-magnetic; however, we find that a magnetic unit can be formed by fusing two Co₆Se₈(PEt₃)₅ superatoms into a [Co₆Se₈(PEt₃)₅]₂ dimer. Theoretical studies indicate that the dumbbell-shaped [Co₆Se₈(PEt₃)₅]₂ dimer has a spin moment of 2μ_B, and the spin density is primarily localized at the interfacial Co-sites where two clusters are fused into a dimer. The dimer has a low ionization energy of 4.17 eV, allowing the dimer to donate charge to C₇₀ during the formation of a cluster assembled material, as seen in recent experiments by Nuckolls and co-workers. The donation of charge causes the dimer's magnetic moment to drop from 2μ_B to 1μ_B. We hypothesize that adding electrons to the dimer, such as doping impurities to the crystal lattice, may enhance the magnetic moment by neutralizing the charged cluster. This reveals a strategy for stabilizing magnetic moments in ligated cluster assemblies.