Photoluminescence of Doped Superatoms M@Au₁₂ (M = Ru, Rh, Ir) Homoleptically Capped by (Ph₂)PCH₂P(Ph₂): Efficient Room-Temperature Phosphorescence from Ru@Au₁₂

A series of doped gold superatoms M@Au₁₂ (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 M@Au₁₂ superatoms had icosahedral motifs with a significantly higher symmetry than that of the pure Au₁₃ counterpart due to different coordination geometries. The Ru@Au₁₂ 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.