Design of Luminescent Heteronuclear Au(I)‐Ag(I) Systems from Aromatic Diazines

By reaction of the polymers [Au 2 Ag 2 (C 6 X 5 ) 4 (OEt 2 ) 2 ] n (X = F, Cl) with the aromatic N‐donor ligands pyrimidine and pyrazine, the new heterometallic complexes [Au 2 Ag 2 (C 6 X 5 ) 4 (pym)] n (X = F ( 1 ), Cl ( 2 )) and [Au 2 Ag 2 (C 6 X 5 ) 4 (pyr)(CH 3 CN) 2 ] n (X = F ( 3 ), Cl ( 4 )) are obtained. The crystal structures of complexes 1 and 3 show the polymerization of the Au 2 Ag 2 tetranuclear units via diazine bridging ligand between two silver centers, and also, in case of complex 1 via aurophilic interactions, leading to a two‐dimensional polymer. In all cases, the optical properties have been studied in solid state at room temperature and 77 K, showing lifetimes in the microseconds range. Finally, this study has been completed with time–dependent density functional theory calculations in the case of complexes 1 and 3 (which present two different emissions) to ascribe the origin of their emissive properties. The molecular orbitals involved in the electronic transitions responsible for the phosphorescence in the case of complex 1 are related to a ligand (C 6 F 5 ) to ligand (pyrimidine) charge transfer ( 3 LL’CT) and to a cluster metal‐centered transition ( 3 MM’). For complex 3 , these molecular orbitals consist of a mixture of a ligand–metal to ligand charge transfer ([Au(C 6 F 5 ) 2 ]–pyrazine) ( 3 LML’CT) and an intraligand transition (within the pyrazine ligand) ( 3 IL).