Luminescent coordination polymers with extended Au(I)–Ag(I) interactions supported by a pyridyl-substituted NHC ligand

Reaction of [Ag(CH3impy)2]PF6, 1, with Au(tht)Cl produces the monometallic Au(I)-species [Au(CH3impy)2]PF6, 2. Treatment of 2 with excess AgBF4 in acetonitrile, benzonitrile or benzylnitrile produces the polymeric species {[AuAg(CH3impy)2(L)](BF4)2}n, (L = CH3CN,3; L = C6H5CN, 4; L = C6H5CH2CN, 5) where the Au(I) centers remain bound to two carbene moieties while the Ag(I) centers are coordinated to two alternating pyridyl groups and a solvent molecule (L). Reaction of 2 with AgNO3 in acetonitrile produces the zig-zag mixed-metal polymer {[AuAg(CH3impy)2(NO3)]NO3}n, 6, that contains a coordinated nitrate ion in place of the coordinated solvent species. All of these polymeric materials are dynamic in solution and dissociate into their respective monometallic components. Compounds 2–6 are intensely luminescent in the solid-state and in frozen solution. All of these complexes were characterized by 1H, 13C NMR, electronic absorption and emission spectroscopy and elemental analysis.

Graphical abstractOne-dimensional, mixed-metal Ag(I)–Au(I) coordination polymers are prepared by treating the homoleptic [Au(CH3impy)2]+ complex with AgBF4 or AgNO3 in the presence of nitrile solvent. The X-ray structures of four polymers reveals short Ag–Au separations. These materials are intensely luminescent the solid state but dissociate into their monomers in solution.Figure optionsDownload full-size imageDownload as PowerPoint slide