Design and Synthesis of Heteroleptic Cyclometalated Iridium(III) Complexes Containing Quinoline-Type Ligands that Exhibit Dual Phosphorescence

The design and synthesis of some cyclometalated iridium(III) complexes containing quinoline-type ligands as ancillary ligands are reported. The emission spectra of Ir(III) complexes Containing a quinolinolate (6, 8, 10) moiety exhibit a single emission peak at ca. 590 nm, resulting in, a red colored emission. However, Ir(III) complexes containing 8-sulfonamidoquinoline ligands (11, 13-21) exhibit two different emission peaks (dual emission) at ca. 500 nm and ca. 600 nm upon excitation at 366 run, resulting in a red colored emission for 11 and a pale yellow-colored emission for 14-18 at 298 K. Especially, a white emission was observed for 19 at 298 and 77 K in dimethyl sulfoxide. The mechanistic studies based on time-dependent density functional theory, calculations and time-resolved emission spectroscopy suggest that this dual emission originates from two independent emission states.