Luminescence in Functionalized Copper Thiolate Clusters - Synthesis and Structural Effects

A series of luminescent polynuclear copper(I) phenyl thiolate clusters with functional groups in the organic ligand shell has been synthesized and characterized by single-crystal X-ray diffraction. Cluster compounds 1-5 with Me2N groups bound to the phenyl thiolate are described and feature different nuclearities and core geometries. The heptanuclear compound 6, which contains both phenyl thiolate and Me3SiO functionalized phenyl thiolate ligands, is an unusual example of a mixed thiolate cluster and exhibits a core almost identical to that of 5. The optical properties of these compounds, which range from binuclear complexes with large CuCu distances to cluster molecules with seven copper atoms and relatively short CuCu distances, have been investigated. Compounds 1-5 show strong absorption below 500 nm. The intense luminescence covers a wide range of the visible spectrum (1: green; 2 and 3: blue; 4 and 5: yellow). It seems likely that the optical transitions occur between orbitals of the thiol ligands and metal-centered orbitals; for the species with short CuCu distances (3-5), these interactions cause a further redshift of the spectra. In addition, the influence of functional groups on optical absorption and emission is shown by the two Cu-7 clusters 5 and 6, which differ solely in the electron-donating nature of their functional groups.