Blue Phosphorescent Iridium(III) Complex. A Reaction Path on the Triplet Potential Energy Surface

The potential energy surfaces associated with the triplet electronic state of the Ir(ppz)3 and Ir(ppy)3 cyclometalated complexes, respectively, are calculated using density functional theory [where ppz = 1-phenylpyrazolyl-N,C2′, ppy = 2-phenylpyridyl]. Both surfaces present a metal-to-ligand charge-transfer energy minimum and a ligand-field energy minimum, connected by a chemical path involving only the rotation of one pyrazolyl or pyridyl group. Unlike Ir(ppy)3, the lowest energy minimum of Ir(ppz)3 is the ligand-field state.