Optical Resolution of Carboxylic Acid Derivatives of Homoleptic Cyclometalated Iridium(III) Complexes via Diastereomers Formed with Chiral Auxiliaries

Synthesis and Performance of Deep-Red Phosphorescent Iridium Complexes with Pyrone as an Auxiliary Ligand

Two bis-cyclometalated heteroleptic iridium complexes incorporating 1-phenylisoquinoline (piq) as the main cyclometalating ligand and 3-hydroxy-2-methyl-4-pyrone (ma) or 2-ethyl-3-hydroxy-4H-pyran-4-one (ema) as the auxiliary ligand, namely Ir(piq)2(ma) (Ir-1) and Ir(piq)2(ema) (Ir-2), were developed and applied as deep-red phosphors in organic light-emitting diodes (OLEDs). The two auxiliary ligands had similar influences on the photophysical, electrochemical, and electroluminescent properties of the iridium complexes. Ir(piq)2(ma) (Ir-1) showed better luminescence performance in a simple phosphorescent OLED compared to the traditional red iridium complex Ir(piq)2(acac) and exhibited a current efficiency of 9.39 cd A-1 (EQE of 12.09%). In contrast, Ir(piq)2(ema) exhibited an efficiency of 8.6 cd A-1 (EQE of 10.19%).

Circularly polarized blue fluorescence based on chiral heteroleptic six-coordinate bis-pyrazolonate-Zn2+ complexes

Applying molecular design to chiral organo-Zn2+ complexes, a new pair of chiral heteroleptic bis-pyrazolonate-Zn2+ enantiomers [Zn(PMBP)2(1R,2R-Chxn)] (R,R-Zn2+; HPMBP = 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone and 1R,2R-Chxn = (1R,2R)-cyclohexane-1,2-diamine) and [Zn(PMBP)2(1S,2S-Chxn)] (S,S-Zn2+; 1S,2S-Chxn = (1S,2S)-cyclohexane-1,2-diamine) have been synthesized and characterized in terms of photophysical and thermodynamic properties. In addition to a small Flack parameter (0.05(3)) associated with the solid-state elucidation of S,S-Zn2+, the circular dichroism (CD) and circularly polarized light (CPL) spectra for the chiral Zn2+ enantiomers show perfect mirror symmetry, establishing that the enantiopure 1,2-diamines successfully induce the optical isomerism of R,R-Zn2+ and S,S-Zn2+. As a result of the combined strong chiral induction capability of chiral 1,2-diamines and excellent photophysical properties of the pyrazolone ligand (PMBP)-, the two Zn2+ enantiomers exhibit high-quality pure blue fluorescence (ΦPL = 9-10%) and significant CPL activity (|glum| = 0.0065-0.0068). The heteroleptic strategy adopted in this study offers a new route to develop high-performance chiroptical luminophores.