Very Short MetallophilicInteractions Induced by Three-Center–Two-ElectronPerhalophenyl Ligands in Phosphorescent Au–Cu Complexes.

The synthesis, structural characterization, and studyof the photoluminescentproperties of the complexes [Au3Cu(C6F5)4(NCCHCHPh)3]n(1) and [Au2Cu(C6Cl5)3(NCCHCHPh)2] (2) have been carried out. The crystal structuresof complexes 1and 2display a common [Au2Cu(C6X5)2(μ-C6X5)(NCCHCHPh)2] fragment built up through atrinuclear Au2Cu unit with a perhalophenyl group actingas a three-center–two-electron bridging ligand. In the caseof 1an additional [Au(C6F5)(NCCHCHPh)]unit is also present in the asymmetric unit. Both complexes are brightlyluminescent in the solid state at room temperature and at 77 K withlifetimes in the nanosecond range for 1and in the microsecondrange for 2. The presence of very short metallophilicinteractions seems to be responsible for the low-energy luminescenceobserved. DFT and time-dependent DFT calculations agree with the experimentalresults and support the idea of that the origin of the emissions arisesfrom metal-based orbitals and arrive at ligand-based orbitals as chargetransfer transitions. [ABSTRACT FROM AUTHOR]