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Due to the ability to emit circularly polarised luminescence (CPL) for application in many areas, chiral luminescent materials have undergone rapid development in recent years. Herein, three chiral copper(I) chloro-bridged dimers R/S-(BINAP)2Cu(μ-X2) (X = Cl, Br and I) based on R/S-2,2′-bis(diphenylphosphino)-1,1′-binaphthalene (R/S-BINAP) ligands were synthesized conveniently at room temperature with high yields above 95%. Though emissions of the compounds in solution are weak, the dimers in the powder form and doped films displayed strong luminescence. Furthermore, the small singlet–triplet energy level gap and the calculated theoretical frontier molecular orbital distribution overlap suggested that these dimers have thermally activated delayed fluorescence characteristics. In addition, R/S-(BINAP)2Cu(μ-X2) doped films showed mirror symmetric circular dichroism and CPL spectra with a high dissymmetry factor (g) above 1 × 10−2. However, the corresponding circularly polarised organic light-emitting diodes (CP-OLEDs) fabricated by the evaporation method based on R/S-(BINAP)2Cu(μ-I2) exhibited a high maximum external quantum efficiency of 21.7%. Notably, the CP-OLEDs also displayed mirror imaged circularly polarised electroluminescence spectra with ‖gEL‖ factors of around 3.0 × 10−3. [ABSTRACT FROM AUTHOR]

Two new iridium(iii) cyclometalated complexes (Ir-TN3T and Ir-TN4T) with 2′,6′-bis(trifluoromethyl)-2,3′-bipyridine (TN3T) and 2′,6′-bis(trifluoromethyl)-2,4′-bipyridine (TN4T) as the cyclometalated ligands and 2-(4,5-diphenyl-4H-1,2,4-triazol-3-yl)phenol (dptp) as the ancillary ligand were developed. Both complexes are green phosphors with high photoluminescence quantum efficiency yields (λmax = 540 nm, Φ = 71.2% for Ir-TN3T and λmax = 513 nm, Φ = 91.0% for Ir-TN4T, respectively) in CH2Cl2 solution at room temperature. Organic light emitting diodes (OLEDs) with single-emitting-layer and double-emitting-layer structures exhibit good performances. Particularly, device D2 with a double-emitting-layer structure based on a Ir-TN4T complex of 8 wt% doped concentration exhibits superior performances with a peak current efficiency of 94.29 cd A−1 and a peak external quantum efficiency (EQEmax) of 31.43%, and the efficiency roll-off is mild. When the luminance reaches 10 000 cd m−2, the EQE value can still be maintained at 30.26%. This study demonstrates that the Ir(iii) complexes containing the ancillary ligand attached with the electron-transporting group of 4-phenyl-4H-1,2,4-triazole could facilitate charge trapping across the bulk of the device and they have promising applications in OLEDs. [ABSTRACT FROM AUTHOR]

Four novel chiral iridium(iii) complexes with triplex stereogenic centers were synthesized by introducing chiral carbon atoms into cyclometalated and ancillary ligands, and separated into eight isomers, which coincide with the old Chinese philosophy Eight Trigrams. The electron circular dichroism and circularly polarized luminescence spectra of four pairs of isomers show perfect mirror images with a dissymmetry factor (glum factor) of around 0.003. [ABSTRACT FROM AUTHOR]

Iridium complexes with a chiral metal center and chiral carbons, Λ/Δ-(dfppy)2Ir(chty-R) and Λ/Δ-(dfppy)2Ir(chty-S), were synthesized and characterized. These isomers have the same steady-state photophysical properties, and obvious offsets in ECD spectra highlight both the chiral sources. Each enantiomeric couple shows mirror-image CPL bands with a dissymmetry factor in the order of 10−3. [ABSTRACT FROM AUTHOR]

Three N,N-bidentate ligands, 5,5′-dibromo-2,2′-bipyridine (L1) and two carbazole containing ligands of 5-bromo-5′-carbazolyl-2,2′-bipyridine (L2), 5,5′-dicarbazolyl-2,2′-bipyridine (L3), and their corresponding rhenium Re(CO)3Cl(L) complexes (ReL1–ReL3) have been successfully synthesized and characterized by elemental analysis, 1H NMR and IR spectra. Their photophysical properties and thermal analysis, along with the X-ray crystal structure analysis of L3and complexes ReL1and ReL3are also described. In CH2Cl2solution at room temperature, all complexes display intense absorption bands at ca.220–350 nm, which can be assigned to spin-allowed intraligand (π→π*) transitions, and the low energy broad bands in the 360–480 nm region are attributed to the metal to ligand charge-transfer dπ(Re)→π* (diimine) (MLCT). The introduction of carbazole moieties improves the MLCT absorption and molar extinction coefficient of these complexes. Upon excitation at the peak maxima, all complexes show strong emissions around 620 nm, which are assigned to dπ(Re)→π* (diimine) MLCT phosphorescence. The photoluminescence lifetime decay of Re(I) complexes were measured and the quantum efficiencies of the rhenium(I) complexes were calculated by using air-equilibrated [Ru(bpy)3]2+·2Cl−aqueous solution as standard (Φstd= 0.028). The complexes with appended carbazole moieties exhibit enhanced luminescence performances relative to ReL1. [ABSTRACT FROM AUTHOR]

Four novel chiral iridium(iii) complexes with triplex stereogenic centers were synthesized by introducing chiral carbon atoms into cyclometalated and ancillary ligands, and separated into eight isomers, which coincide with the old Chinese philosophy Eight Trigrams. The electron circular dichroism and circularly polarized luminescence spectra of four pairs of isomers show perfect mirror images with a dissymmetry factor (g lum factor) of around 0.003.

Iridium complexes with a chiral metal center and chiral carbons, Λ/Δ-(dfppy) 2 Ir(chty-R) and Λ/Δ-(dfppy) 2 Ir(chty-S), were synthesized and characterized. These isomers have the same steady-state photophysical properties, and obvious offsets in ECD spectra highlight both the chiral sources. Each enantiomeric couple shows mirror-image CPL bands with a dissymmetry factor in the order of 10 -3 .

Three N,N-bidentate ligands, 5,5'-dibromo-2,2-bipyridine (L1) and two carbazole containing ligands of 5-bromo-5'-carbazolyl-2,2-bipyridine (L2), 5,5'-dicarbazolyl-2,2'-bipyridine (L3), and their corresponding rhenium Re(CO)3Cl(L) complexes (ReL1-ReL3) have been successfully synthesized and characterized by elemental analysis, 1H NMR and IR spectra. Their photophysical properties and thermal analysis, along with the X-ray crystal structure analysis of L3 and complexes ReL1 and ReL3 are also described. In CH2Cl2 solution at room temperature, all complexes display intense absorption bands at ca. 220-350 nm, which can be assigned to spin-allowed intraligand (pi-->pi*) transitions, and the low energy broad bands in the 360-480 nm region are attributed to the metal to ligand charge-transfer d(Re)-->pi* (diimine) (MLCT). The introduction of carbazole moieties improves the MLCT absorption and molar extinction coefficient of these complexes. Upon excitation at the peak maxima, all complexes show strong emissions around 620 nm, which are assigned to d(Re)-->pi* (diimine) MLCT phosphorescence. The photoluminescence lifetime decay of Re(I) complexes were measured and the quantum efficiencies of the rhenium(I) complexes were calculated by using air-equilibrated [Ru(bpy)3]2+ x 2 Cl- aqueous solution as standard (phi(std) = 0.028). The complexes with appended carbazole moieties exhibit enhanced luminescence performances relative to ReL1.