Mixed-Carbene Cyclometalated Iridium Complexes with Saturated Blue Luminescence

Cyclometalated iridium complexes have emerged as top-performing emitters in organic light-emitting diodes (OLEDs) and other optoelectronic devices. A persistent challenge has been the development of cyclometalated iridium complexes with deep blue luminescence that have the requisite color purity, efficiency, and stability to function in color displays. In this work we report a new class of cyclometalated iridium complexes with saturated blue luminescence. These complexes have the general structure Ir(C^C:NHC)2(C^C:ADC), where C^C:NHC is an N-heterocyclic carbene (NHC) derived cyclometalating ligand and C^C:ADC is a different type of cyclometalating ligand featuring an acyclic diaminocarbene (ADC). The complexes are prepared by a cascade reaction that involves nucleophilic addition of propylamine to an isocyanide precursor followed by base-assisted cyclometalation of the ADC intermediate. All three emit deep blue light with good quantum efficiencies (ΦPL = 0.13–0.48) and color profiles very close to the ideal primary blue standards for color displays.