A new series of dinuclear Au(i) complexes linked by diethynylpyridine groups

A series of novel digold complexes incorporating ethynyl pyridine derivatives as a spacer unit, [(R₃P)Au(C≡C)X(C≡C)Au(PR₃)] (R = Ph, X = 2,5-pyridine (1); R = Cy (cyclohexane), X = 2,5-pyridine (2); R = Ph, X = 2,6-pyridine (3); R = Ph, X = 2,5′-bipyridine (4); R = Ph, X = 2,6′-bipyridine (5)), has been synthesised. All the complexes have been characterised spectroscopically and the structures determined by single-crystal X-ray crystallography. The central (CC)(X)(CC) unit is essentially linear for complexes 1, 2 and 4 and kinked for complexes 3 and 5, but only in 1, with the shortest spacer group and the less bulky phosphine ligand, is there evidence of d¹⁰⋯d¹⁰ Au⋯Au interactions (Au–Au 3.351(2) Å). The solution UV/visible absorption and emission spectra for all the complexes are similar to those of the free ligands suggesting that the spectra are dominated by π–π* ligand-centred transitions and this is confirmed by DFT calculations.