Gold(I) Complexes of Brominated Azadipyrromethene Ligands

Azadipyrromethenes are luminescent, red-light absorbing dyes that readily bind BF2+ and metals. Their framework allows for structural modification at the phenyl arms and the two pyrrolic carbon positions. Here we report five new gold(I) complexes with azadipyrromethene ligands brominated at the pyrrolic carbons and/or the four phenyl substituents. New complexes are characterized by multinuclear NMR spectroscopy, X-ray crystallography, optical absorption and emission spectroscopy, and elemental analysis. The new compounds have a perturbed two-coordinate geometry in the crystalline state, with gold(I) binding one dimethylphenylphosphine ancillary ligand and one pyrrole nitrogen of the azadipyrromethene. The second azadipyrromethene pyrrole nitrogen perturbs the linear coordination. These complexes maintain the absorption features of the free ligands. Excitation in the near-ultraviolet generates emission in the near-UV and visible regions. Density-functional theory calculations indicate that the photoproperties of the new compounds arise almost entirely from the conjugated ligands and not from the (phosphine)gold(I) fragments.