Solid-state luminescence and crystal structures of novel gold(I) benzenethiolate complexes

A series of mononuclear bis(benzenethiolato)gold(I) complexes, [n-Bu4N][Au(SC6H4R)(2)] [R = H (1), o-Me (2), o-OMe (3), o-Cl (4), m-Me (5), m-OMe (6), m-Cl (7), p-Me (8), p-OMe (9) or p-Cl (10)] showed luminescence in the solid state at room temperature. The emission maxima ranged from 438 (blue emission) to 529 nm (green emission). The luminescence of these complexes is affected by substituent effects: electron-donating substituents (R = Me or OMe) on the benzene rings tend to shift the emission maxima toward shorter wavelengths, but the electron-withdrawing substituents (R = Cl) make the emission maxima shift toward longer wavelengths when compared to the maximum of the non-substituted species. This suggests that the luminescence properties could come from excited states due to a metal-to-ligand charge-transfer (MLCT) or ligand-centred (LC) transition. Complexes 2, 4, and 7 show normal linear S-Au-S geometries but exhibit no gold-gold interactions owing to the steric hindrance of the bulky counter cations, [n-Bu4N](+), which prevent the approach of two neighboring gold atoms. Both 2 and 4 show asymmetric configurations of the two thiolate ligands. On the other hand, 7 shows a completely symmetric configuration, where the gold atom is positioned at a center of symmetry.