Synthesis, structure and luminescence of 1,8-diaurionaphthalenes

Abstract

Reaction of 1,8-dilithionaphthalene with [AuCl(Et₃P)] or [Au₂Cl₂(μ-dppm)] (dppm = bis(diphenylphosphinomethane)) in Et₂O/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 Å. Complex 2 reacts with AgPF₆ in THF/CH₂Cl₂ to afford a dicationic Au₄Ag₂ 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 Au₂AgAu₂Ag six-membered ring in which the metal centers are connected by Au–Au (av. 2.84 Å) and Au–Ag (av. 2.75 Å) 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.