Molecular design of luminescence ion probes for various cations based on weak gold(I)⋯gold(I) interactions in dinuclear gold(I) complexes

Abstract

A series of luminescent dinuclear gold(I) complexes with different crown ether pendants, [Au2(P∧P)(S-B15C5)2] [S-B15C5 = 4′-mercaptobenzo-15-crown-5, P∧P = bis(dicyclohexylphosphino)methane (dcpm) (1), bis(diphenylphosphino)methane (dppm) (2)] and [Au 2(P∧P)(S-B18C6)2] [S-B18C6 = 4′-mercaptobenzo- 18-crown-6, P∧P = dcpm (3), dppm (4)], and their related crown-free complexes, [Au2(P∧P)(SC6H3(OMe) 2-3,4)2] [P∧P = dcpm (5), dppm (6)], were synthesized. The low-energy emission of the mercaptocrown ether-containing gold(I) complexes are tentatively assigned as originated from states derived from a S → Au ligand-to-metal charge transfer (LMCT) transition. The crown ether-containing gold(I) complexes showed specific binding abilities toward various metal cations according to the ring size of the crown pendants. Spectroscopic evidence was provided for the metal-ion-induced switching on of the gold⋯gold interactions upon the binding of particular metal ions in a sandwich binding mode.