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 d(10)center dot center dot center dot d(10) Au center dot center dot center dot Au interactions (Au-Au 3.351(2) angstrom). 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 pi-pi* ligand-centred transitions and this is confirmed by DFT calculations.