Controllable Synthesis and Luminescence Behavior of Tetrahedral Au@Cu 4 and Au@Ag 4 Clusters Supported by tris(2-Pyridyl)phosphine.

We report herein a family of polynuclear complexes, [Au@Ag 4 (Py 3 P) 4 ]X 5 and [Au@Cu 4 (Py 3 P) 4 ]X 5 [X = NO 3 , ClO 4 , OTf, BF 4 , SbF 6 ], containing unprecedented Au-centered Ag 4 and Cu 4 tetrahedral cores supported by tris(2-pyridyl)phosphine (Py 3 P) ligands. The [Au@Ag 4 ] 5+ clusters are synthesized via controlled substitution of the central Ag(I) ion in all-silver [Ag@Ag 4 ] 5+ precursors by the reaction with Au( tht )Cl, while the [Au@Cu 4 ] 5+ cluster is assembled through the treatment of a pre-organized [Au(Py 3 P) 4 ] + metallo-ligand with 4 equiv of a Cu(I) source. The structure of the Au@M 4 clusters has been experimentally and theoretically investigated to reveal very weak intermolecular Au-M metallophilic interactions. At ambient temperature, the designed compounds emit a modest turquoise-to-yellow luminescence with microsecond lifetimes. Based on the temperature-dependent photophysical experiments and DFT/TD-DFT computations, the emission observed has been assigned to an MLCT or LLCT type depending on composition of the cluster core.