Anionic Polymers Formed by Dinuclear Rhodium Units and Dicyanide Silver/Gold Moieties

The synthesis, characterization and structural determination of four complexes with formula (PPh4)n[Rh2(µ–O2CPh)4Au(CN)2]n (1) and Kn[Rh2(µ–O2CR)4M(CN)2]n (M = Au, R = OEt (2), OMe (3); M = Ag, R = OMe (4)) are described. In all cases, the [CN-M-CN]– (M = Au, Ag) group is bridging the axial positions of the dirhodium units giving one-dimensional chains. The packing of the chains in the solid state depends on the nature of the carboxylate group of the dimetallic unit, the counterion present in the complex and the metal itself. The most striking change is observed in the Kn[Rh2(μ-O2CCH2OMe)4Au(CN)2]n complex (3) where the chains are positioned perpendicular to each other with an Au···Au interchain distance of 2.963 Å. The emission studies of this complex upon excitation at 350 nm show a clear broad emission band centered at 430 nm, while no luminescence is observed for the other compounds. The appearance of emission properties only in the case of complex 3 can be explained by its short aurophilic inter-actions.