Spectroscopic evidence for argentophilicity in structurally characterized luminescent binuclear silver(I) complexes

Abstract

A spectroscopic and structural investigation of binuclear silver(I) complexes supported by aliphatic phosphine ligands, namely [Ag(PCy 3)(O 2CCF 3)] 2 (1); [Ag 2(μ-dcpm) 2]X 2 (X = CF 3SO 3, 2; PF 6, 3; dcpm = bis(dicyclohexylphosphino)methane), and [Ag 2(μ-dcpm)(μ-O 2CCF 3) 2] (4), is described. X-ray structural analyses of 1-4 reveal Ag-Ag separations of 3.095(1), 2.948 (av), 2.923 (av), and 2.8892(9) Å, respectively. Due to the optical transparency of the phosphine ligands, the UV-vis absorption band at 261 nm in CH 3CN for 2 and 3 is assigned to a 4dσ* → 5pσ transition originating from Ag(I)-Ag(I) interactions. The argentophilic nature of this band is verified by the resonance Raman spectrum of 2 with 273.9 nm excitation, where virtually all of the Raman intensity appears in the Ag-Ag stretch fundamental (80 cm -1) and overtone bands. Complexes 2 and 3 exhibit photoluminescence in the solid state at room temperature.