Phosphorescent Iridium(III) Complexes of Cyclometalated 5‑Aryl‑1<i>H</i>‑1,2,4-Triazole Ligands: Structural, Computational, Spectroscopic, and Device Studies

Abstract

Ir­(III) complexes of cyclometalated 5-aryl-1<i>H</i>-1,2,4-triazole ligands are highly efficient, phosphorescent emitters. We describe herein a series of <i>fac</i>-IrL₃ complexes, in which the nature of aryl substituents are shown to strongly affect emission wavelength over the range 453–499 nm. Computational and structural studies indicate that for aryl groups the point of attachment and dihedral angle with respect to the cyclometalated ring influence emission color. Significantly, this degree of color tuning may be achieved without resorting to electron-withdrawing or -donating groups. Photo- and electroluminescence device studies of the different emitters indicate that they are generally highly efficient: photoluminescent efficiencies >90% and external quantum efficiencies of up to 22% are observed