Blue Phosphorescence with High Quantum Efficiency Engaging the Trifluoromethylsulfonyl Group to Iridium Phenylpyridine Complexes.

Incorporation of an electron-withdrawing -SOCF substituent to cyclometalating C^N-phenylpyridine (ppy) ligand resulted in an expected blue-shifted phosphorescence in the corresponding homoleptic complex, showing the emission of λ = 464 nm at 300 K. One of its heteroleptic derivatives, modified by a pyrazolyl borate LX ligand, , exhibited further blue-shifted phosphorescence of λ = 460 nm at 300 K. Cyclic voltammograms (CVs) and density-functional theory (DFT) calculations supported the efficacy of the electron-withdrawing capability of the SOCF substituent lowering HOMO energy and obtained widened bandgaps and resumed blue emissions for all of the iridium complexes studied.

Stable Blue Phosphorescence Iridium(III) Cyclometalated Complexes Prompted by Intramolecular Hydrogen Bond in Ancillary Ligand.

Improvement of the stability of blue phosphorescent dopant material is one of the key factors for real application of organic light-emitting diodes (OLEDs). In this study, we found that the intramolecular hydrogen bonding in an ancillary ligand from a heteroleptic Ir(III) complex can play an important role in the stability of blue phosphorescence. To rationalize the role of intramolecular hydrogen bonding, a series of Ir(III) complexes is designed and prepared: Ir(dfppy)2(pic-OH) (1a), Ir(dfppy)2(pic-OMe) (1b), Ir(ppy)2(pic-OH) (2a), and Ir(ppy)2(pic-OMe) (2b).