Gold-decorated 2,2′-bipyridine ligands with sterically demanding phosphanes

Treatment of 4,4′-diethynyl-2,2′-bipyridine with (3-tolyl)3PAuCl or tBu3PAuCl leads to the gold(I) phosphane decorated bis(alkynyl)-2,2′-bipyridine complexes 5 and 6 respectively. These complexes have been fully characterized and their single crystal structures reveal that the bulky nature of the phosphane substituents preclude intermolecular Au…Au close contacts. Both compounds are photoactive and emissive in solution, but when irradiated at 238 nm (for 5) or 234 nm (for 6), immediate decay of the emission spectrum is observed with growth of new bands; the observations are compared with related compounds in which the gold(I) phosphane units contain less sterically demanding substituents.