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.