Zhong-Yi Li

Highly efficient green phosphorescent organic light-emitting diodes with low efficiency roll-off based on iridium(III) complexes bearing oxadiazol-substituted amide ligands

Two novel iridium(III) complexes [Ir(ppy)2(PhOXD)] (1, ppy = 2-phenylpyridine, PhOXD = N-(5-phenyl-1,3,4-oxadiazol-2-yl)-benzamide) and [Ir(ppy)2(POXD)] (2, POXD = N-(5-phenyl-1,3,4-oxadiazol-2-yl)-diphenylphosphinic amide) have been designed and synthesized, and their photoluminescence and electrochemistry properties were investigated. At room temperature, complexes 1 and 2 show green emissions at about 502 and 506 nm with photoluminescence quantum yields (PLQYs) of 0.03 and 0.05 in CH2Cl2 solutions, respectively. In the 5 wt% doped poly(methyl methacrylate) (PMMA) film, the PLQYs (0.42 for complex 1, 0.52 for complex 2, respectively) increase significantly. The organic light emitting diodes (OLEDs) with the structure of ITO/HAT-CN (dipyrazino[2,3-f:2′,3′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile), 10 nm)/TAPC (1,1-bis[4-(di-p-tolylamino)phenyl]cyclohexane, 40 nm)/Ir complexes (10 wt%): mCP (1,3-bis(9H-carbazol-9-yl)benzene, 20 nm)/TPBi (1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene, 40 nm)/LiF (1 nm)/Al (100 nm) show good performances. In particular, device G2 based on complex 2 shows superior performances with a peak current efficiency (ηc) of 64.7 cd A−1 and a peak power efficiency (ηp) of 42.5 lm W−1 with low electroluminescence efficiency roll-off. The ηc value still remains over 60.6 cd A−1 even at a luminance of 10 000 cd m−2, which indicates that introducing electron transporting 1,3,4-oxadiazole and diphenyl phosphoryl groups into iridium complexes is an effective means of achieving efficient phosphors in OLEDs.

Linking heterometallic Cu–Ln chain units with a 2-methylenesuccinate bridge to form a 2D network exhibiting a large magnetocaloric effect

Four two-dimensional heterometallic Cu–Ln coordination polymers based on the 2-methylenesuccinic acid (H2MSA) ligand, {[Ln2Cu(MSA)4(H2O)6]·2H2O}n(Ln = La (1); Gd (2); Tb (3); Dy (4)), have been obtained under hydrothermal conditions. Complexes 1–4 bear a feature of one-dimensional [Ln2Cu] chains linked by 2-methylenesuccinate (MSA2−) bridges to form a 2D layer structure. Magnetic studies suggest the presence of weak antiferromagnetic Gd⋯Gd coupling and weak ferromagnetic Cu⋯Gd coupling in the 1D [Gd2Cu] chain unit of 2. The magnetic entropy change (−ΔSm) reached 36.05(1) J K−1 kg−1 for 2, making it an attractive refrigerant for low-temperature applications.

Linking cobalt–water chains with cis-1,4-cyclohexanedicarboxylate bridges to form a 2D network exhibiting spin-canted antiferromagnetism

A two-dimensional magnetic network, [Co(cis-CHDA)(μ2-H2O)(H2O)2]·2H2O (1), featuring one-dimensional water-bridged Co2+ chains that are linked by pure cis-1,4-cyclohexanedicarboxylate (cis-CHDA) bridges has been obtained. Magnetic studies show that 1 exhibits spin-canted antiferromagnetism with spin-glass behavior at low temperature.

Iridium(III) complexes bearing oxadiazol-substituted amide ligands: color tuning and application in highly efficient phosphorescent organic light-emitting diodes

By adjusting the conjugation degrees of the phenylquinoline-based cyclometalated ligands, yellow, orange to red phosphorescent iridium(III) complexes [Ir(bzq)2(POXD)] (1, bzq = 7,8-benzoquinoline, POXD = N-(5-phenyl-1,3,4-oxadiazol-2-yl)-diphenylphosphinic amide), [Ir(pq)2(POXD)] (2, pq = 2-phenylquinoline) and [Ir(piq)2(POXD)] (3, piq = 1-phenylisoquinoline) have been designed and prepared. Their photophysical and electrochemical studies and theoretical calculations were performed, and [Ir(bzq)2(POXD)] was also determined by X-ray crystallography. At room temperature, complexes 1–3 exhibit efficient phosphorescence emissions at about 539, 592 and 614 nm with photoluminescence quantum yields (PLQYs) of 0.21, 0.06 and 0.06 in CH3CN solutions, respectively. In the 5 wt% doped poly(methyl methacrylate) (PMMA) film, the PLQYs (0.35 for complex 1, 0.37 for complex 2 and 0.18 for complex 3, respectively) increase significantly. Organic light emitting diodes (OLEDs) based on these complexes were fabricated to evaluate their potential application. The yellow device in the configuration ITO/2-TNATA (25 nm)/NPB (5 nm)/TCTA (10 nm)/complex 1 (10 wt%):mCP (10 nm)/complex 1 (10 wt%):TPBi (10 nm)/TPBi (40 nm)/Liq (1 nm)/Al (100 nm) shows excellent performance with a maximum luminance of 24 080 cd m−2, maximum current efficiencies of 70.1 cd A−1 and maximum external quantum efficiencies of 21.3% along with low efficiency roll-off.

Syntheses and structures of three organic–inorganic hybrids with Different 2D structural types constructed from rare earth polymers and Keggin-Type Silicotungstates

ABSTRACT Three organic-inorganic hybrid materials, namely [RE(H2O)3K(H2O)2 (pddc)2]2H4[SiW12O40]·2H2O (RE = Pr (1), Nd (2); H2pddc = 3,4-pyridine dicarboxylic acid) and [Y(pzdc)(H2O)3]2H2[SiW12O40]·4H2O (3) (H2pzdc = 2,3-pyrazine dicarboxylic acid) have been synthesized and characterized by elemental analyses, IR spectra, UV spectra, TG analyses and X-ray crystallography. Single crystal X-ray analyses reveal that 1–3 all exhibit 2D layer structures. Interestingly, 1 and 2 are isostructural differenting from 3. In 3, the polyoxoanions [SiW12O40]4− connect the rare earth cations [Y(pzdc)(H2O)3]2+ via Y–O bonds forming a (4, 4)-connected 2D topology net with Schläfli symbol of 32.62.72. GRAPHICAL ABSTRACT Three organic-inorganic hybrids {[Ln(H2O)3][K(H2O)2](pddc)2}2H4[SiW12O40]·2H2O (Ln = Pr (1), Nd (2); H2pddc = 3,4-pyridine dicarboxylic acid) and [Y(H2O)3(pzdc)]2H2[SiW12O40]·4H2O (3) (H2pzdc = 2,3-pyrazine dicarboxylic acid) have been synthesized from two different ligands and exhibit two different types of 2D structures.