Highly Selective Aluminum(III) Ion Sensing with Luminescent Iridium(III) Complexes Bearing a Distorted 2,2'-Bipyridine-3,3'-diol Moiety Utilizing a Rigidified Seven-Membered Chelate Ring.

To create an ion sensor utilizing a rigidified seven-membered chelate ring, we developed two Ir(III) complexes with 2,2'-bipyridine-3,3'-diol (bpy(OH), ) ligands as reaction centers, namely ([Ir(ppy){bpy(O)(OH)}], ppy = 2-phenylpyridine) and ([Ir(bzq){bpy(O)(OH)}], bzq = benzo[]quinoline), and evaluated their reactivities toward metal ions by spectrophotometry. When they are reacted with Al, these complexes exhibit dramatic enhancements in emission intensity (775-fold for and 51.0-fold for ) and distinct orange to green changes in emission color.