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.