Chiral‐Zn(NTf2)2‐Complex‐Catalyzed Diastereo‐ and Enantioselective Direct Conjugate Addition of Arylacetonitriles to Alkylidene Malonates

Chiral N,N′‐dioxide/Zn(NTf₂)₂ complexes were demonstrated to be highly effective in the direct asymmetric conjugate addition of arylacetonitriles to alkylidene malonates under mild conditions. A wide range of substrates were tolerated to afford their corresponding products in moderate‐to‐good yields with high diastereoselectivities (82:18–>99:1 d.r.) and enantioselectivities (81–99 % ee). The reactions performed well, owing to the high Lewis acidity of the metal triflimidate and a ligand‐acceleration effect. The N,N′‐dioxide also benefited the deprotonation process as a Brønsted base. The catalytic reaction could be performed on the gram‐scale with retention of yield, diastereoselectivity, and enantioselectivity. The products that contained functional groups were ready for further manipulation. In addition, a possible catalytic model was proposed to explain the origin of the asymmetric induction.     

Stability and Deactivation of Au/Fe2O3 Catalysts for CO Oxidation at Ambient Temperature and Moisture

Various Au/Fe₂O₃ catalysts were prepared by the coprecipitation method, and CO oxidation was studied at ambient temperature and in the presence of water vapor in the feed. It was found that the precipitation method and the calcination temperatures have a significant effect on the catalytic performance of CO oxidation. The stability is related to the particle size of metallic gold and -Fe₂O₃ and the oxidation state of gold and the iron crystalline phase. The sintering of the gold particles, the reduction of oxide gold to metallic gold, the accumulation of carbonate, and a decrease in the specific surface area were observed during the reaction, which may contribute to the deactivation of Au/Fe₂O₃ catalysts.     

Thienoacene‐Fused Pentalenes: Syntheses,Structures, Physical Properties and Applications for Organic Field‐Effect Transistors

Three soluble and stable thienoacene‐fused pentalene derivatives ( 1 – 3 ) with different π‐conjugation lengths were synthesized. X‐ray crystallographic analysis and density functional theory (DFT) calculations revealed their unique geometric and electronic structures due to the interaction between the aromatic thienoacene units and antiaromatic pentalene moiety. As a result, they all possess a small energy gap and show amphoteric redox behaviour. Time dependent (TD) DFT calculations were used to explain their unique electronic absorption spectra. These new compounds exhibited good thermal stability and ordered packing in solid state and thus their applications in organic field‐effect transistors (OFETs) were also investigated. The highest field‐effect hole mobility of 0.016, 0.036 and 0.001 cm² V^?1 s^?1 was achieved for solution‐processed thin films of 1 – 3 , respectively.     

Efficient red phosphorescent OLEDs based on the energy transfer from interface exciplex: the critical role of constituting molecules

A novel acceptor material,9-(4′-(4,6-diphenyl-1,3,5-triazin-2-yl)-[1,1′-biphenyl]-3-yl)-9H-carbazole(o-DTPPC)was developed to form interface exciplex with commonly used donors,to maximize the performances of red phosphorescent organic light emitting diodes(PHOLEDs).It is found that the exciplex involving 4,4′-(cyclohexane-1,1-diyl)bis(N,N-di-p-tolylaniline)(TAPC)exhibits the most significant thermally activated delayed fluorescence(TADF)property,derived from the high triplet energy level as well as strong hole-transporting ability of TAPC.Intriguingly,it is the same donor-acceptor combination which achieved the highest device efficiency when adopted as the host for red PHOLEDs.Maximum efficiencies as high as31.36 cd A~(-1),17.95 lm W~(-1),and 21.01%for the current efficiency,power efficiency and external quantum efficiency,respectively with low efficiency roll-off were realized.The improved performance can be attributed to the efficient TADF properties of the interface exciplex-forming host constituting TAPC,benefiting the F?rster energy transfer.The article first underlines the importance of the constituting molecules in the interface exciplex-forming hosts,shedding new insight about the choice of interface exciplex as the host for PHOLEDs,which may lead to even higher performances,paving their ways towards practical applications.     

Mean Residence Time of CO2 Molecules in Flexible ZIF-8 Cages Explored by Molecular Dynamics Simulations

The adsorption sites and diffusion mechanism of CO2 molecules in the flexible Zn（MeIM）2 （MeIM=2-methylimidazole） （ZIF-8） have been investigated by grand canonical Monte Carlo and molecular dynamics simulations. A reasonable time correlation function is for the first time constructed to explore the mean residence time of CO2 molecules in the ZIF-8 cages, suggesting that C02 molecules can remain in the same cage for up to several tens of picoseconds. Furthermore, we find that the mean residence time almost linearly increases with the increasing pressure （or loading） at 273 and 298 K.     

Comparative study of LiNi0.05Mn1.95O4 powders prepared by different materials for Li-ion battery

LiNi_0.05Mn_1.95O₄ powders were prepared by manganese tetraoxide (MTO) and electrolytic manganese dioxide (EMD). The phase identification, surface morphology, and electrochemical properties of the prepared powders were studied by X-ray diffraction, scanning electron microscopy, cyclic voltammetry, and galvanostatic charge?Cdischarge experiments. Compared to LiNi_0.05Mn_1.95O₄ powders prepared by EMD, LiNi_0.05Mn_1.95O₄ powders prepared by MTO show better crystallinity. Both powders possess a typical cubic structure with uniform particle size. The specific capacity and coulombic efficiency of LiNi_0.05Mn_1.95O₄ powders prepared by MTO are higher than the one prepared by EMD. The capacity retention of LiNi_0.05Mn_1.95O₄ powders prepared by MTO cycled 30 times at room temperature and 55?°C are 98.3% and 90.6%, respectively, which are much higher than those of 86.63% and 77.7% for the one prepared by EMD. LiNi_0.05Mn_1.95O₄ powders prepared by MTO show higher specific capacity and better cycling performance than the one prepared by EMD.     

Unpaired 3d Electrons on Atomically Dispersed Cobalt Centres in Coordination Polymers Regulate both Oxygen Reduction Reaction (ORR) Activity and Selectivity for Use in Zinc–Air Batteries

Reversible oxygen conversion is important for various green energy technologies. Herein we synthesize a series of bimetallic coordination polymers by varying the Ni/Co ratio and using HITP (HITP=2,3,6,7,10,11-hexaiminotriphenylene) as the ligand, to interrogate the role of metal centres in modulating the activity of the oxygen reduction reaction (ORR). Co₃HITP₂ and Ni₃HITP₂ are compared. Unpaired 3d electrons in Co₃HITP₂ result in less coplanarity but more radical character. Thus, despite of a reduced crystallinity and conductivity, the best ORR activity, comparable to 20 % Pt/C, is obtained for Co₃HITP₂, showing the 3d orbital configuration of the metal centre promotes ORR. Experimental and DFT studies show a transition of ORR pathway from four-electron for Co₃HITP₂ to two-electron for Ni₃HITP₂. Rechargeable zinc–air batteries using Co₃HITP₂ as the air cathode catalyst demonstrate excellent energy efficiency and stability.     

catena‐Poly[[[2‐(2‐chlorophenoxy)‐N′‐(2‐oxidobenzylidene‐κO)acetohydrazidato‐κ2N′,O]copper(II)]‐μ‐morpholine‐κ2N:O]

In the title compound, {[Cu(C₁₅H₁₁ClN₂O₃)(C₄H₉NO)]_n, the Cu^II cation has square‐pyramidal geometry. The morpholine ligand serves as a bridge to link two symmetry‐related metal atoms, resulting in an infinite chain structure along the a axis. Adjacent chains are extended into a two‐dimensional layered structure via hydrogen bonds formed between morpholine and amide N atoms [N—H...N = 2.971 (3) Å].