Photophysical Properties of Highly Efficient Blue-Green Emitting Cationic Iridium (III) Complexes Containing Two 2-Phenylbenzothiazole Ligands and One Diphosphine Ligand

Abstract

Two novel phosphorescent heteroleptic cationic Ir(III) complexes, Ir(bt) 2 (dmpe) (Ir1) and Ir (bt) 2 (dppe) (Ir2), where bt is 2-phenylbenzothiazole, dmpe is 1,2-bis(dimethylphosphino)ethane, and dppe is 1,2-bis(diphenylphosphino)ethane, were designed and synthesized. Their photophysical and electrochemical properties and the X-ray structure of the Ir1 complex were investigated. The prepared Ir(III) complexes exhibited blue-green emissions at 503-538 nm with vibronic fine structures in dichloromethane solution and PMMA film, implying that the lowest excited states are dominated by ligand-based 3 π-π* transitions. The π-acceptor ability of the diphosphine ancillary ligand leads to blue-shift emission. The room temperature photoluminescent quantum yields (PLQYs) of Ir1 and Ir2 were 52% and 45%, respectively, in dichloromethane solution. These high PLQYs resulted from steric hindrances by the bulky cationic iridium complexes. The crystal structure of Ir1 was determined by X-ray crystallography, which revealed that central iridium adopted a distorted octahedral structure coordinated with two bt ligands (N^C) and one dmpe ligand (P^P) showing cis C-C and trans N-N dispositions. The bent nature of the dmpe ligand resulted in a relatively wide bite angle of 83.83 o of P-Ir-P.

Photo- and Electroluminescent Neutral Iridium(III) Complexes Bearing Imidoylamidinate Ligands

“…amine, and 2-phenylbenzo[d]thiazole were purchased from Aldrich. The complexes [(bt) 2 Ir(μ-Cl)] 2 , 66 Ir1, 28 and [(bt) 2 Rh(μ-Cl)] 2 66 were prepared via the previously reported procedures. The TG/DTG measurements were performed on a NETZSCH TG 209 F1 Libra thermoanalyzer.…”

“…Benzo­[ d ]­thiazol-2-amine, benzo­[ d ]­oxazol-2-amine, 1 H -benzo­[ d ]­imidazol-2-amine, 1-methyl-1 H -benzo­[ d ]­imidazol-2-amine, and 2-phenylbenzo­[ d ]­thiazole were purchased from Aldrich. The complexes [( bt ) 2 Ir­(μ-Cl)] 2 , Ir1 , and [( bt ) 2 Rh­(μ-Cl)] 2 were prepared via the previously reported procedures. The TG/DTG measurements were performed on a NETZSCH TG 209 F1 Libra thermoanalyzer.…”

Orange–Yellow Phosphorescent Iridium(III) Complex for Solution‐processed Organic Light‐Emitting Diodes: Structural, Optical and Electroluminescent Properties of Bis(2‐phenylbenzothiazole)[2‐(2‐hydroxyphenyl)benzothiazole]iridium(III)

“…Some benzothiazole derivatives containing benzothiazole moiety and aromatic ring have interesting photochemical properties due to the presence of two different chromophores in a molecule, and the benzothiazole‐based metal complexes are of much interest in designing and synthesizing luminescent materials . Recently, we reported blue–green emitting heteroleptic cyclometalated iridium(III) complexes composed of 2‐phenylbenzothiazole and diphosphine ligand, and proposed they were potential phosphors for highly efficient solution‐processed electroluminescent devices such as organic light‐emitting diodes (OLEDs) and light‐emitting electrochemical cells (LECs). Industrially, OLEDs are usually manufactured by vapor deposition method .…”