The promoting role of minor amount of water in solvent-free hydrogenation of halogenated nitrobenzenes

This study shows that minor amount of water plays a very important role in solvent-free hydrogenation of halogenated nitrobenzenes. For dried sponge Pd, the reaction cannot occur in the absence of water. For Pd/C catalyst, minor amount of water reduces the induction time, increases the reaction rate and reaction TOFs. Water might enhance the diffusion, adsorption and dissociation of H2 on Pd catalysts.     

差示扫描量热法测定比沙可啶的纯度

建立差示扫描量热法测定比沙可啶原料药样品纯度的方法。考察了炉体气氛、升温速率、称样量3个因素对差示扫描量热法测定结果的影响,确定差示扫描量热法最佳实验条件:升温速率为2.0 K/min,称样量为2.0~4.0 mg,炉内气体为静态空气。差示扫描量热法测定比沙可啶样品纯度为99.86%,测定结果的相对标准偏差为0.02%(n=6),差示扫描量热法测定比沙可啶样品纯度值与HPLC测定结果具有良好的一致性。该方法可以快速、准确地测定比沙可啶化学纯度,为比沙可啶纯度测定提供了一种新的分析方法。     

An Enzymatic N-Acylation Step Enables the Biocatalytic Synthesis of Unnatural Sialosides

Chitin is one of the most abundant and cheaply available biopolymers in Nature. Chitin has become a valuable starting material for many biotechnological products through manipulation of its N-acetyl functionality, which can be cleaved under mild conditions using the enzyme family of de-N-acetylases. However, the chemoselective enzymatic re-acylation of glucosamine derivatives, which can introduce new stable functionalities into chitin derivatives, is much less explored. Herein we describe an acylase (CmCDA from Cyclobacterium marinum) that catalyzes the N-acylation of glycosamine with a range of carboxylic acids under physiological reaction conditions. This biocatalyst closes an important gap in allowing the conversion of chitin into complex glycosides, such as C5-modified sialosides, through the use of highly selective enzyme cascades.     

Modification of Hole Transport Layers for Fabricating High Performance Non‐fullerene Polymer Solar Cells

Interfacial engineering is expected to be a feasible strategy to improve the charge transport properties of the hole transport layer (HTL), which is of crucial importance to boost the device performance of organic solar cells (OSCs). In this study, two types of alcohol soluble materials, 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F₄‐TCNQ) and di‐tetrabutylammoniumcis–bis(isothiocyanato)bis (2,2’‐bipyridyl‐4,4’‐dicarboxylato) ruthenium(II) (N719) dye were selected as the dopant for HTL. The doping of F₄‐TCNQ and N719 dye in poly (ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) with and without integrating a graphene quantum‐dots (G‐QDs) layer has been explored in poly[[2,6′‐4‐8‐di(5‐ethylhexylthienyl)benzo[1,2‐b:3,3‐b]dithiophene][3‐fluoro‐2[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thio‐phenediyl:(2,2′‐((2Z,2′Z)‐(((4,4,9, 9‐tetrakis(4‐hexylphenyl)‐4,9‐dihydro‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene‐2,7‐diyl)bis(4‐((2‐ethylhexyl)oxy)thiophene‐5,2‐diyl))bis(methanylylidene))bis(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile (PTB7‐Th:IEICO‐4F) OSCs. The power conversion efficiency of the non‐fullerene OSCs has been increased to 10.12% from 8.84%. The influence of HTL modification on the nano‐morphological structures and photophysical properties is analyzed based on the comparative studies performed on the control and modified devices. The use of chemical doping and bilayer strategy optimizes the energy level alignment, nanomorphology, hole mobility, and work‐function of HTL, leading to considerable reduction of the leakage current and recombination losses. Our work demonstrates that the doping of HTL and the incorporation of G‐QDs layer to constitute a bilayer HTL is an promising strategy to fabricate high performance non‐fullerene polymer solar cells     

Quantitative Design of Bright Fluorophores and AIEgens by the Accurate Prediction of Twisted Intramolecular Charge Transfer (TICT)

Inhibition of TICT can significantly increase the brightness of fluorescent materials. Accurate prediction of TICT is thus critical for the quantitative design of high‐performance fluorophores and AIEgens. TICT of 14 types of popular organic fluorophores were modeled with time‐dependent density functional theory (TD‐DFT). A reliable and generalizable computational approach for modeling TICT formations was established. To demonstrate the prediction power of our approach, we quantitatively designed a boron dipyrromethene (BODIPY)‐based AIEgen which exhibits (almost) barrierless TICT rotations in monomers. Subsequent experiments validated our molecular design and showed that the aggregation of this compound turns on bright emissions with ca. 27‐fold fluorescence enhancement, as TICT formation is inhibited in molecular aggregates.     

Conversion of Methane into Methanol and Ethanol over Nickel Oxide on Ceria–Zirconia Catalysts in a Single Reactor

The conversion of methane into alcohols under moderate reaction conditions is a promising technology for converting stranded methane reserves into liquids that can be transported in pipelines and upgraded to value‐added chemicals. We demonstrate that a catalyst consisting of small nickel oxide clusters supported on ceria–zirconia (NiO/CZ) can convert methane to methanol and ethanol in a single, steady‐state process at 723 K using O₂ as an abundantly available oxidant. The presence of steam is required to obtain alcohols rather than CO₂ as the product of catalytic combustion. The unusual activity of this catalyst is attributed to the synergy between the small Lewis acidic NiO clusters and the redox‐active CZ support, which also stabilizes the small NiO clusters.     

Ultrathin Co3S4 Nanosheets that Synergistically Engineer Spin States and Exposed Polyhedra that Promote Water Oxidation under Neutral Conditions

Development of efficient and affordable electrocatalysts in neutral solutions is paramount importance for the renewable energy. Herein, we report that the oxygen evolution reaction (OER) performance of Co₃S₄ under neutral conditions can be enhanced by exposed octahedral planes and self‐adapted spin states in atomically thin nanosheets. A HAADF image clearly confirmed that the active octahedra with Jahn–Teller distortions were exposed exclusively. Most importantly, in the atomically thin nanosheets, the spin states of Co³⁺ in the octahedral self‐adapt from low‐spin to high‐spin states. As a result, the synergistic effect endow the Co₃S₄ nanosheets with superior OER performance, with exceptional low onset overpotentials of circa 0.31 V in neutral solutions, which is state‐of‐the‐art among inorganic non‐noble metal compounds.     

Novel metallocene catalysts for syndiotactic polystyrene

A series of new half-metallocene complexes of titanium containing siloxy ligands and a new bimetallic titanocene complex (compound 1) with a crystallographically determined structure have been prepared. When activated with methylaluminoxane (MAO), they showed high activities toward polymerization of styrene with high syndiotacticity. Origin of the high activity and syndiotacticity found in this work was investigated systematically by comparison with polymerization results using other known complexes.     

Reactivity of the Hydroxy Groups in Melezitose and Their Selective Protection

The reactivity of melezitose hydroxy groups was studied by tritylation in pyridine with subsequent acetylation. After partial detritylation of the products, acetyl group transfer from position 4 to 6 was observed. The structure of the prepared melezitose derivatives was established on the basis of their IR, ¹H, ¹³C, and ¹H-¹H COSY NMR, and mass spectra (fast atom bombardment), as well as from the results of model calculations performed with the aid of SGI Indigo Molecule-Pattern-Work-Station software package (Biosym) where the potential energy function was approximated with the CVFF potential. The reactivity of primary hydroxy groups in melezitose was found to decrease in the following order: 6' > 6 6' > 1'.