Three-Coordinate, Phosphine-Ligated Azadipyrromethene Complexes of Univalent Group 11 Metals

Tetraarylazadipyrromethenes are Lewis basic, red-light absorbing dyes with optical properties conducive to sensing and therapeutic applications. Recently, transition metal complexes of these ligands have been described. Here, we report a series of three-coordinate Group 11 complexes of unsubstituted and methoxy-substituted tetraarylazadipyrromethenes. In each, two pyrrole nitrogens chelate a d10 metal ion; triphenyl- or triethylphosphine occupies a third coordination site. New complexes are characterized by multinuclear NMR, X-ray crystallography, optical absorption and emission spectroscopy, and elemental analysis. Solid-state structures show trigonal planar geometries about the metal centers, and reveal pervasive intra- and intermolecular π-stacking interactions. Visible light absorption intensifies with metal binding, in some cases shifting to longer wavelengths. The complexes weakly luminesce in the red region; emission wavelengths and quantum yields are similar to those of free azadipyrromethenes. Methoxy-substitution on the ligand red-shifts optical features, whereas substitution of triethylphosphine for triphenylphosphine in the third coordination site has minimal structural or spectral consequences.