Synthesis, structure and luminescence of 1,8-diaurionaphthalenes

Reaction of 1,8-dilithionaphthalene with [AuCl(Et(3)P)] or [Au(2)Cl(2)(mu-dppm)] (dppm = bis(diphenylphosphinomethane)) in Et(2)O/THF leads to formation of bis(triethylphosphine)-1,8-diaurionaphthalene (1) and dppm-1,8-diaurionaphthalene (2), respectively. The dppm ligand present in complex 2 bridges the two gold centers leading to formation of short intramolecular Au-Au distances of av. 2.85 angstrom. Complex 2 reacts with AgPF(6) in THF/CH(2)Cl(2) to afford a dicationic Au(4)Ag(2) complex which has been isolated as the bis(hexafluorophosphate) salt (3). In this cluster, two molecules of 2 sandwich two Ag cations resulting in the formation of a Au(2)AgAu(2)Ag six-membered ring in which the metal centers are connected by Au-Au (av. 2.84 angstrom) and Au-Ag (av. 2.75 angstrom) metallophilic interactions. This cluster is further stabilized by short Ag-C interactions involving some of the naphthalene carbon atoms. The luminescence spectra of 2 and 3 have been recorded. Both complexes display relatively broad emission bands centered at 540 nm which result, at least in part, from the heavy atom induced phosphorescence of the naphthalene chromophore.