A new series of isostructural, brilliantly luminescent gold-silver complexes having the formula [Au3(mu3-E)Ag(PPh2py)3](BF4)2 where E = O, S, Se and Ph2Ppy = 2-diphenylphosphinopyridine has been synthesized and characterized. The structural core of these complexes is a Au3Ag metallophilically linked tetrahedron with a group-16 atom functioning as a mu3-ligand capping the three gold atoms. In the solid state, pairs of clusters are joined by two unsupported aurophilic interactions. The emission energy changes strikingly in going from O (blue) to S (yellow) and Se (orange). The luminescence from the E = O system is the first to be reported for a gold(I) oxo system. Additionally, the luminescent 4-methylpyridyl analogue with E = S has been prepared and structurally characterized. For E = S, Se, the change in emission energy with mu3-bridging atom provides a sound basis for an LMMCT assignment of the excited state while lifetime measurements support its spin-forbidden nature. Frozen glass measurements indicate the presence of a higher-energy emitting state for these systems, and for the E = O system, either LMMCT or metal-centered cluster-based emission can be proposed.

Metalloligands of stoichiometry [AuCl(P−N)] have been obtained by the reaction of the heterofunctional phosphines P−N = PPh2py, PPh2CH2CH2py, or PPhpy2 with [AuCl(tht)] (tht = tetrahydrothiophene). Reactions of these metalloligands with several metal compounds have afforded heteropolynuclear species which exhibit luminescent properties. The stoichiometries depend on the molar ratio and the heterometal. Thus, the reaction with [Cu(NCMe)4]+ in a molar ratio 2:1 gives the trinuclear compounds [Au2CuCl2(P−N)2]+, in which the structure and Au···Cu interactions depend on the phosphine ligand. With rhodium and iridium derivatives the reactivity is different leading to complexes of the type [AuMCl2(cod)(P−N)] for P−N = PPh2py, PPhpy2, and [Au2M2Cl(cod)2(P−N)2]Cl with PPh2CH2CH2py. Using [MCl2(NCPh)2] (M = Pd, Pt) in a 2:1 molar ratio yields [Au2MCl4(P−N)2] and in a 1:1 molar ratio [AuPdCl3(μ3-PPhpy2)]. Several compounds have been characterized by X-ray diffraction showing in many cases short Au···M distances. The luminescence of these derivatives has been studied. The metalloligands display bands assigned to intraligand (IL) transitions. For the bimetallic (Au/M) systems the luminescence depends on the heterometal present and on the metallophilic interactions. The most important excitations in the relevant energy range were assigned essentially a MMLCT character (from Rh/Ir and Au to ligands) based on density functional theory (DFT) calculations in selected complexes. The luminescence behavior in Rh/Ir [AuMCl2(cod)(PPh2py)] complexes was interpreted on the basis of the different nature of the half occupied orbitals in the triplet state.