Two new blue-phosphorescent Ir(III) cyclometalated complexes demonstrating the pushing-up effects of amino on levels of Pi-type molecular orbitals

Orbital interactions between nitrogen's 2p-orbital, 2p(N), and the higher-lying HOMO/LUMO would push-up the latter even higher. This destabilization effect exerted by an amino explains the high-lying LUMO of the 2,2′-dipyridyl amine (HDPA) ancillary ligand, as well as the high-lying LUMO in Ir(ppy)₂HDPA⁺ (ppy = 2-phenylpyridine). The pi-destabilization effect on MOs exerted by a fluoro must be incorporated into consideration to explain the site-dependent characteristics observed by related color-tuning studies. Two new blue phosphorescent fluorinated Ir(ppy) ₂HDPA⁺ complexes have been synthesized by introducing fluoro(s) at suitable phenyl-carbon(s): having small 2p_π(C) content in HOMO and/or large 2p_π(C) content in LUMO.