Phosphorescence Color Alteration by Changing Counter Anions on Tetrahedral Gold(I) Complexes; Intra- and Interligand π-π Interactions

Tetrahedral gold(I) complexes containing the diphosphane ligand [dppb = 1,2-bis(diphenylphosphanyl)benzene], [Au(dppb)(2)]X {X= Cl (1), BF(4) (2) and PF(6) (3)}, were prepared and characterized by X-ray structural analysis. Complexes 1 and 2 have almost the same structure with two dppb ligands, which are symmetrically coordinated to the Au atom in the crystal. However, the two dppb ligands of 3 are asymnmetrically bound to the gold(I) stom in the crystal. Both colorless complexes 1 and 2 exhibit intense blue phosphorescence with peak maxima at 481 nm (Phi(p)= 0.86) for 1 and 490 nm (Phi(p)= 0.90) for 2, respectively. The pale yellow complex 3 shows weak yellow-orange phosphorescence with a peak maximum at 596 nm (Phi(p) = 0.04). A small conformational change in the crystal, which is caused by changing the counter anion, dramatically alters the optical properties of the tetrahedral gold(I) complexes in the solid state. The difference in the absorption and phosphorescence spectra between 1 and 3 has been interpreted on the basis of molecular arrangement including packing structures of the complexes and time-dependent density functional theory (TD-DFT) calculations. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)