Heteropolynuclear gold complexes with metallophilic interactions: modulation of the luminescent properties

Metalloligands of stoichiometry [AuCl(P-N)] have been obtained by the reaction of the heterofunctional phosphines P-N = PPh(2)py, PPh(2)CH(2)CH(2)py, or PPhpy(2) 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 [Au(2)CuCl(2)(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 [AuMCl(2)(cod)(P-N)] for P-N = PPh(2)py, PPhpy(2), and [Au(2)M(2)Cl(cod)(2)(P-N)(2)]Cl with PPh(2)CH(2)CH(2)py. Using [MCl(2)(NCPh)(2)] (M = Pd, Pt) in a 2:1 molar ratio yields [Au(2)MCl(4)(P-N)(2)] and in a 1:1 molar ratio [AuPdCl(3)(μ(3)-PPhpy(2))]. 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 [AuMCl(2)(cod)(PPh(2)py)] complexes was interpreted on the basis of the different nature of the half occupied orbitals in the triplet state.