Li-ion-conductive Li2TiO3-coated Li[Li0.2Mn0.51Ni0.19Co0.1]O2 for high-performance cathode material in lithium-ion battery

Journal of Solid State Electrochemistry - Li2TiO3 is used as a novel coating material to modify Li(Li0.2Mn0.51Ni0.19Co0.1)O2 electrode to enhance the electrochemical performance of the host...     

Visible-Light-Mediated Click Chemistry for Highly Regioselective Azide–Alkyne Cycloaddition by a Photoredox Electron-Transfer Strategy

Click chemistry focuses on the development of highly selective reactions using simple precursors for the exquisite synthesis of molecules. Undisputedly, the Cu^I-catalyzed azide–alkyne cycloaddition (CuAAC) is one of the most valuable examples of click chemistry, but it suffers from some limitations as it requires additional reducing agents and ligands as well as cytotoxic copper. Here, we demonstrate a novel strategy for the azide–alkyne cycloaddition reaction that involves a photoredox electron-transfer radical mechanism instead of the traditional metal-catalyzed coordination process. This newly developed photocatalyzed azide–alkyne cycloaddition reaction can be performed under mild conditions at room temperature in the presence of air and visible light and shows good functional group tolerance, excellent atom economy, high yields of up to 99 %, and absolute regioselectivity, affording a variety of 1,4-disubstituted 1,2,3-triazole derivatives, including bioactive molecules and pharmaceuticals. The use of a recyclable photocatalyst, solar energy, and water as solvent makes this photocatalytic system sustainable and environmentally friendly. Moreover, the azide–alkyne cycloaddition reaction could be photocatalyzed in the presence of a metal-free catalyst with excellent regioselectivity, which represents an important development for click chemistry and should find versatile applications in organic synthesis, chemical biology, and materials science.     

基于面式-三(2-(4-三氟甲基苯基)吡啶)合铱配合物为发光中心的高效绿光有机电致发光器件

用经典的方法合成了面式-三(2-(4-三氟甲基苯基)吡啶)合铱配合物(fac-Ir(tfmppy)₃), 并得到了其晶体结构。在CH₂Cl₂溶液中Ir(tfmppy)₃的发射光谱显示出了峰值位于525 nm的π→π^*跃迁吸收以及金属到配体电荷转移(MLCT)吸收, 色坐标(CIE)为(0.31, 0.62), 量子效率计算为4.59%(以Ru(bpy)₃]Cl₂为参照)。以Ir(tfmppy)₃为发光中心, 制备并研究了有机电致发光器件:ITO/TAPC (60 nm)/Ir(tfmppy)₃ (x%):mCP (30 nm)/TPBi (60 nm)/LiF (1 nm)/Al (100 nm)。4%掺杂浓度的器件在4 197 cd·m^-2的亮度下显示的最大电流效率为33.95 cd·A^-1, 在12.7 V时的最大亮度为43 612 cd·m^-2, 色坐标(CIE)为(0.31, 0.61)。利用瞬态电致发光法(transient electroluminescence (EL))、在1 300 (V·cm^-1)^1/2的电场强度下Ir(tfmppy)₃配合物的电子迁移率测定为4.24×10^-6 cm²·(V·s)^-1。非常接近于常用的电子传输材料八羟基喹啉铝(Alq₃)的电子迁移率。     

两种红光铱配合物的合成和电致发光性能研究

以二(二苯基磷酰)胺(Htpip)作为辅助配体,与主配体2-(2,4-二氟苯基)异喹啉和2-(4-三氟甲基苯基)异喹啉合成了红光铱磷光配合物Ir(dfpiq)2tpip和Ir(tfmpiq)2tpip并得到了晶体结构。在CH2Cl2中发射光谱主要是MLCT发射,峰位置分别为622和600 nm,量子效率分别为15%和17%,而HOMO/LUMO能级分别是-4.80/-2.58和-4.73/-2.57 eV。在1150~1300(V·cm-1)1/2电场范围,Ir(dfpiq)2tpip的电子迁移率为6.61~8.49×10-6cm2·V-1·s-1,Ir(tfmpiq)2tpip的电子迁移率为6.08~6.61×10-6cm2·V-1·s-1。ITO/TAPC(60 nm)/Ir-complex(15wt%):CBP(50 nm)/TPBi(60 nm)/LiF(1 nm)/Al(100 nm)中基于Ir(dfpiq)2tpip的器件最大安培效率和功率效率分别为4.71 cd·A-1和1.82 lm·W-1,12.0 V时达到的最大亮度为18 195 cd·m-2。基于Ir(tfmpiq)2tpip的器件最大安培效率和功率效率分别为3.47 cd·A-1和1.51 lm·W-1,12.4 V时达到的最大亮度为14 676 cd·m-2。     

Efficient and Saturated Red Light-Emitting Electrochemical Cells Based on Cationic Iridium(III) Complexes with EQE up to 9.4 %

Solid-state light-emitting electrochemical cells (LECs) have several advantages, such as low-voltage operation, compatibility with inert metal electrodes, large-area flexible substrates, and simple solution-processable device architectures. However, most of the studies on saturated red LECs show low or moderate device efficiencies (external quantum efficiency (EQE) <3.3 %). In this work, we demonstrate a series of five red-emitting cationic iridium complexes ( RED1- - RED5 ) with 2,2′-biquinoline ligands and test their electroluminescence (EL) characteristics in LECs. The Commission Internationale de l′Eclairage (CIE) 1931 coordinates for the LECs based on these complexes are all beyond the National Television System Committee (NTSC) red standard point (0.67, 0.33). The maximal EQE of the neat-film RED1 -based LECs reaches 7.4 %. The reddest complex, RED3 , is doped in the blue-emitting host complex, BG , to fabricate host–guest LECs. The maximal EQE of the host–guest LECs (1 wt % complex RED3 ) reaches 9.4 %, which is among the highest reported for the saturated red LECs.     

Configurationally Stable Platinahelicene Enantiomers for Efficient Circularly Polarized Phosphorescent Organic Light-Emitting Diodes

Chiral materials with circularly polarized luminescence (CPL) are potentially applicable for 3D displays. In this study, by decorating the pyridinyl-helicene ligands with -CF₃ and -F groups, the platinahelicene enantiomers featured superior configurational stability, as well as high sublimation yield (>90 %) and clear CPPL properties, with dissymmetry factors (|g_PL|) of approximately 3.7×10⁻³ in solution and about 4.1×10⁻³ in doped film. The evaporated circularly polarized phosphorescent organic light-emitting diodes (CP-PhOLEDs) with two enantiomers as emitters exhibited symmetric CPEL signals with |g_EL| of (1.1–1.6)×10⁻³ and decent device performances, achieving a maximum brightness of 11 590 cd m⁻², a maximum external quantum efficiency up to 18.81 %, which are the highest values among the reported devices based on chiral phosphorescent Pt^II complexes. To suppress the effect of reverse CPEL signal from the cathode reflection, the further implementation of semitransparent aluminum/silver cathode successfully boosts up the |g_EL| by over three times to 5.1×10⁻³.     

利用吡啶衍生物主配体共轭效应调控铱配合物发光颜色

利用2-苯基吡啶及其衍生物为主配体、四苯基膦酰亚胺为辅助配体合成了3个铱配合物Ir（ppy）₂tpip（Hppy：2-苯基吡啶,Htpip：四苯基膦酰亚胺）、Ir（npy）₂tpip（Hnpy：2-（1-萘基）吡啶）和Ir（pnpy）₂tpip（Hpnpy：2-（9-菲基）吡啶）。它们的结构通过1HNMR和MALDI-TOF质谱进行了表征,其中配合物Ir（ppy）₂tpip还进一步通过晶体结构分析验证。主配体从苯环到萘环和菲环的改变增加了配合物的π共轭,减小了能级差,导致了3种配合物的磷光发射光谱从516nm红移到600和633nm（从绿光到红光）,发光量子效率也从0.36增加到0.51和0.53。从量化计算的结果可以看出,这种共轭效应增加了主配体的电子密度,提高了配合物的LUMO能级。配合物结构和发射性质之间的关系规律为设计不同发光颜色的铱配合物提供了思路。     

两个磷光铱配合物的合成和性质研究

由于具有P=O键,二(二苯基膦酰)胺(tetraphenylimidodiphosphinate acid,Htpip)作为辅助配体引入Ir(III)配合物中,可以提高配合物的电子迁移率和器件的效率。采用氟取代的2-(4-氟苯基)吡啶(F4-ppy)为主配体、以Htpip和三氟甲基取代的Htfmtpip为辅助配体合成了2个铱配合物Ir(F4-ppy)2(tpip)和Ir(F4-ppy)2(tfmtpip)。晶体结构中Ir原子的配位几何构型均为八面体构型,Ir(F4-ppy)2(tpip)属于正交晶系Pbca空间群,而Ir(F4-ppy)2(tfmtpip)属于单斜晶系P21/c空间群。配合物都具有较好的热稳定性,Ir(F4-ppy)2(tpip)和Ir(F4-ppy)2(tfmtpip)的初始分解温度分别为385和395℃。配合物Ir(F4-ppy)2(tfmtpip)的氧化和还原峰较配合物Ir(F4-ppy)2(tpip)分别向正电压移动了大约0.134和0.12 V,相应的HOMO和LUMO能级分别降低了0.14和0.43 eV。在室温、1×10-5mol·L-1的CH2Cl2溶液中Ir(F4-ppy)2(tpip)和Ir(F4-ppy)2(tfmtpip)的最大磷光发射峰分别位于492和495 nm,量子效率分别为9.2%和16.4%。结果表明在辅助配体上引入4个三氟甲基后不仅可以提高配合物的热稳定性和电化学稳定性,并且可以调控配合物的HOMO/LUMO能级和发光效率。     

Cyclometallated iridium phosphors with amino acid ancillary ligand for intracellular imaging

Two new iridium complexes, (dfppy)₂Ir(L-alanine) (dfppy=2-(2,4-difluorophenyl)pyridine) and (piq)₂Ir(L-alanine) (piq=L-phenylisoquinoline) were prepared with L-alanine as ancillary ligand. The two complexes show bright greenish-blue and red emission respectively. Theoretic study demonstrated that the emission nature of these complexes is mainly determined by the main ligand. And their improved aqueous solubility and the retained quantum yield favor their application in cell imaging. Intracellular imaging suggested that these two complexes have fine cell membrane permeability and is mainly distributed in cytoplasm. This study displayed a new strategy to design aqueous soluble phosphorescent cyclometallated Ir(Ⅲ) complex via introducing amino acid as ancillary ligand.     

Planar Chiral Multiple Resonance Thermally Activated Delayed Fluorescence Materials for Efficient Circularly Polarized Electroluminescence

Chiral boron/nitrogen doped multiple resonance thermally activated delayed fluorescence (MR-TADF) emitters are promising for highly efficient and color-pure circularly polarized organic light-emitting diodes (CP-OLEDs). Herein, we report two pairs of MR-TADF materials (Czp-tBuCzB, Czp-POAB) based on planar chiral paracyclophane with photoluminescence quantum yields of up to 98 %. The enantiomers showed symmetric circularly polarized photoluminescence spectra with dissymmetry factors |g_PL| of up to 1.6×10⁻³ in doped films. Meanwhile, the sky-blue CP-OLEDs with (R/S)-Czp-tBuCzB showed an external quantum efficiency of 32.1 % with the narrowest full-width at half-maximum of 24 nm among the reported CP-OLEDs, while the devices with (R/S)-Czp-POAB displayed the first nearly pure green CP electroluminescence with |g_EL| factors at the 10⁻³ level. These results demonstrate the incorporation of planar chirality into MR-TADF emitter is a reliable strategy for constructing of efficient CP-OLEDs.