A substituted pyridazine acts as a sensitizer in mononuclear heteroleptic Ln(iii) complexes.

We report herein a family of polynuclear complexes, [Au@Ag4(Py3P)4]­X5 and [Au@Cu4(Py3P)4]­X5 [X = NO3, ClO4, OTf, BF4, SbF6], containing unprecedented Au-centered Ag4 and Cu4 tetrahedral cores supported by tris­(2-pyridyl)­phosphine (Py3P) ligands. The [Au@Ag4]5+ clusters are synthesized via controlled substitution of the central Ag­(I) ion in all-silver [Ag@Ag4]5+ precursors by the reaction with Au­(tht)­Cl, while the [Au@Cu4]5+ cluster is assembled through the treatment of a pre-organized [Au­(Py3P)4]+ metallo-ligand with 4 equiv of a Cu­(I) source. The structure of the Au@M4 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.

Chromophore-containing phosphines produce highly solvatochromic gold(i) fluorophores. Their combination with red-emitting Eu centers offers a facile approach to dual emissive complexes with widely tunable luminescence characteristics.