A dodecanethiolate-protected Pd₁Au₂₄(SC₁₂H₂₅)₁₈ cluster, which is a mono-Pd-doped cluster of the well understood magic gold cluster Au₂₅(SR)₁₈ , was isolated in high purity using solvent fractionation and high-performance liquid chromatography (HPLC) after the preparation of dodecanethiolate-protected palladium–gold bimetal clusters. The cluster thus isolated was identified as the neutral [Pd₁Au₂₄(SC₁₂H₂₅)₁₈]⁰ from the retention time in reverse phase columns and by elemental analyses. The LDI mass spectrum of [Pd₁Au₂₄(SC₁₂H₂₅)₁₈]⁰ indicates that [Pd₁Au₂₄(SC₁₂H₂₅)₁₈]⁰ adopts a similar framework structure to Au₂₅(SR)₁₈ , in which an icosahedral Au₁₃ core is protected by six [–S–Au–S–Au–S–] oligomers. The optical absorption spectrum of [Pd₁Au₂₄(SC₁₂H₂₅)₁₈]⁰ exhibits peaks at ∼690 and ∼620 nm, which is consistent with calculated results on [Pd₁@Au₂₄(SC₁H₃)₁₈]⁰ in which the central gold atom of Au₂₅(SC₁H₃)₁₈ is replaced with Pd. These results strongly indicate that the isolated [Pd₁Au₂₄(SC₁₂H₂₅)₁₈]⁰ has a core–shell [Pd₁@Au₂₄(SC₁₂H₂₅)₁₈]⁰ structure in which the central Pd atom is surrounded by a frame of Au₂₄(SC₁₂H₂₅)₁₈. Experiments on the stability of the cluster showed that Pd₁@Au₂₄(SC₁₂H₂₅)₁₈ is more stable against degradation in solution and laser dissociation than Au₂₅(SC₁₂H₂₅)₁₈. These results indicate that the doping of a central atom is a powerful method to increase the stability beyond the Au₂₅(SR)₁₈ cluster.

A series of doped gold superatoms [email protected]₁₂ (M = Ru, Rh, Ir) was synthesized by capping with the bidentate ligand (Ph₂)PCH₂P(Ph₂). A single-crystal X-ray diffraction analysis showed that all the [email protected]₁₂ superatoms had icosahedral motifs with a significantly higher symmetry than that of the pure Au₁₃ counterpart due to different coordination geometries. The [email protected]₁₂ superatom exhibited a room-temperature phosphorescence with the highest quantum yield of 0.37 in deaerated dichloromethane. Density functional theory calculations suggested that the efficient phosphorescence is ascribed to a rapid intersystem crossing due to the similarity between the singlet and triplet excited states in terms of structure and energy.