Influence of Intermolecular Interactions on Valence Tautomeric Behaviors in Two Polymorphic Dinuclear Cobalt Complexes

Two polymorphic structures have been well determined in a valence tautomeric (VT) dinuclear cobalt complex. These polymorphs showed distinct thermal‐ and photomagnetic behavior, and are thus ideal for studying the “pure” intermolecular factors to VT transitions. In polymorph 1A , the VT cations are arranged head‐to‐waist with their neighbors and exhibit weak π???π interactions, resulting in a gradual and incomplete thermal VT transition. In contrast, the cations in polymorph 1B are arranged head‐to‐tail and exhibit relatively strong π???π interactions, leading to an abrupt and complete thermal VT transition with adjustable hysteresis loop at around room temperature. The VT process for both polymorphs can be induced by light, but the light‐excited state of 1B? 2H₂O has a higher thermal relaxation temperature than that of 1A? 3H₂O.     

Phase and Interface Engineering of Platinum–Nickel Nanowires for Efficient Electrochemical Hydrogen Evolution

The design of high‐performance electrocatalysts for the alkaline hydrogen evolution reaction (HER) is highly desirable for the development of alkaline water electrolysis. Phase‐ and interface‐engineered platinum–nickel nanowires (Pt‐Ni NWs) are highly efficient electrocatalysts for alkaline HER. The phase and interface engineering is achieved by simply annealing the pristine Pt‐Ni NWs under a controlled atmosphere. Impressively, the newly generated nanomaterials exhibit superior activity for the alkaline HER, outperforming the pristine Pt‐Ni NWs and commercial Pt/C, and also represent the best alkaline HER catalysts to date. The enhanced HER activities are attributed to the superior phase and interface structures in the engineered Pt‐Ni NWs.     

Thermally Induced Intra‐Carboxyl Proton Shuttle in a Molecular Rack‐and‐Pinion Cascade Achieving Macroscopic Crystal Deformation

Proton transport via dynamic molecules is ubiquitous in chemistry and biology. However, its use as a switching mechanism for properties in functional molecular assemblies is far less common. In this study, we demonstrate how an intra‐carboxyl proton shuttle can be generated in a molecular assembly akin to a rack‐and‐pinion cascade via a thermally induced single‐crystal‐to‐single‐crystal phase transition. In a triply interpenetrated supramolecular organic framework (SOF), a 4,4′‐azopyridine (azpy) molecule connects to two biphenyl‐3,3′,5,5′‐tetracarboxylic acid (H₄BPTC) molecules to form a functional molecular system with switchable mechanical properties. A temperature change reversibly triggers a molecular movement akin to a rack‐and‐pinion cascade, which mainly involves 1) an intra‐carboxyl proton shuttle coupled with tilting of the azo molecules and azo pedal motion and 2) H₄BPTC translation. Moreover, both the molecular motions are collective, and being propagated across the entire framework, leading to a macroscopic crystal expansion and contraction.     

Copper‐Catalyzed Reaction Cascade of Thiophenol Hydroxylation and S‐Arylation through Disulfide‐Directed C−H Activation

Copper‐catalyzed thiophenol C?H activation is described. Through an initial attempt to conduct C‐arylation with arylboronic acid, a rather surprising sequential C?H activation and S‐arylation was discovered. Mechanistic investigation revealed the disulfide intermediate as the key component in directing C?H oxidation. The overall reaction proceeded under mild conditions with molecular oxygen as the oxidant. Discovery of disulfide as the directing group provides a potential new direction for catalytic C?H functionalization under mild conditions.     

Post‐Synthetic Polymerization of UiO‐66‐NH2 Nanoparticles and Polyurethane Oligomer toward Stand‐Alone Membranes for Dye Removal and Separation

Metal–organic frameworks (MOFs) are widely used as porous materials in the fields of adsorption and separation. However, their practical application is largely hindered by limitations to their processability. Herein, new UiO‐66‐Urea‐based flexible membranes with MOF loadings of 50 ( 1 ), 60 ( 2 ), and 70 wt % ( 3 ) were designed and prepared by post‐synthetic polymerization of UiO‐66‐NH₂ nanoparticles and a polyurethane oligomer under mild conditions. The adsorption behavior of membrane 3 towards four hydrophilic dyes, namely, eosin Y (EY), rhodamine B (RB), malachite green (MG), and methylene blue (MB), in aqueous solution was studied in detail. It exhibits strong adsorption of EY and RB but weak adsorption of MG and MB in aqueous solution. Owing to the selective adsorption of these hydrophilic dyes, membrane 3 can remove EY and RB from aqueous solution and completely separate EY/MB, RB/MG, and RB/MB mixtures in aqueous solution. In addition, the membrane is uniformly textured, easily handled, and can be reused for dye adsorption and separation.     

新型固定化pH梯度毛细管等电聚焦方法用于蛋白分离

通过化学键合建立一种固定化pH梯度的方法,用于毛细管等电聚焦分离蛋白质.采用微流控泵驱动毛细管内的聚焦区带,通过调节泵的流量,从而调节聚焦区带的迁移速度.该方法避免了自由溶液聚焦时两性电解质所带来的影响,实现了高灵敏度及检测波长自由选择等优点,适用于两步法毛细管电泳等电聚焦分离蛋白质等两性电解质.本文考察了对牛血清白蛋白和血红蛋白两种蛋白质混合物的分离,证明了该方法可行.     

高分辨电感耦合等离子体质谱仪测定中亚山地冰川雪冰中超痕量元素

在超净实验条件下,利用高分辨电感耦合等离子体质谱仪直接测定雪冰样品中浓度在1ng/L~100μg/L之间的多种超痕量元素Al、Fe、Mn、Co、Cu、Zn、Sr、Sb、Cd、CsBa、Tl、Pb和Bi的实验方法进展。在测定过程中灵敏度的变化可通过监测ArAr质谱峰的变化进行校正,并建立了数学校正公式。以1%HNO3为空白溶液获得了各元素的检出限(ng/L)分别为:Al40、Mn6、Fe40、Co2.74、Cu9.6、Zn20、Sr0.03、Sb0.15、Cs0.04、Ba0.4、Tl0.07、Pb0.8和Bi0.05。利用标准参考物质SLRS-4对测试方法的准确度进行了评价。研究了在硝酸含量分别为0.5%、1%、2%和4%时雪冰中超痕量元素质谱信号强度的变化特点。测定结果发现,对于污化层样品,当硝酸的含量为1%时痕量元素的质谱信号强度最大;对于非污化层样品,痕量元素的质谱信号强度在硝酸含量为0.5%时较大,但与硝酸含量为1%时的质谱信号强度相比变化率小于10%。结合中亚山地冰川雪冰中痕量元素浓度差别大的特点,确定硝酸在样品中的含量为1%为合适的酸度。并对卓奥友峰和珠穆朗玛峰雪坑样品进行了分析方法的重复性研究。     

Aryl to aryl palladium migration in the Heck and Suzuki coupling of o-halobiaryls

A novel 1,4-palladium migration between the o- and o'-positions of biaryls has been observed in organopalladium intermediates derived from o-halobiaryls. The organopalladium intermediates generated by this migration have been trapped either by a Heck reaction employing ethyl acrylate or by Suzuki cross-coupling using arylboronic acids. This palladium migration can be activated or deactivated by choosing the appropriate reaction conditions. Chemical and computational evidence supports the presence of an equilibrium that correlates with the C-H acidity of the available arene positions.     

Colloid chemical reaction route to the preparation of nearly monodispersed perylene nanoparticles: size-tunable synthesis and three-dimensional self-organization

By employing a colloid chemical reaction method we demonstrate the preparation of organic nanoparticles composed of perylene molecules (PeNPs) based on the reduction of perylene perchlorate by Br- anions in the presence of cetyl trimethyl ammonium bromide (CTA+Br-) in acetonitrile. A discrete nucleation event, followed by a slower controlled growth on the existing particles, is identified during formation of PeNPs. By changing the growth parameters, such as the monomer concentration and the method of injection, quasi-spherical PeNPs with controllable sizes from 25 to 90 nm could be obtained. The homogeneous solution phase of this method makes it capable of large-scale synthesis of PeNPs with a size distribution (<10%) that is improved by formation of a protective layer of CTA+ around the PeNPs. The three-dimensional, hierarchical self-organization of 25-nm PeNPs building blocks is observed to form nanobelts and square nanorods, possibly templated by the CTA+ lamellar micelle structures in acetonitrile. Spectroscopic results reveal two kinds of trends in the development of the optical properties of perylene as they evolve from the molecular to the bulk phase in the nanometer range. The so-called size dependence is evidenced by a switch from Y-type to E-type excimers as the size of the PeNPs increased from 25 to 90 nm. As the 25-nm PeNPs organize into nanobelts or square nanorods the oscillator strength of the Y-type excimers is relatively enhanced. That is, collective phenomena develop as the proximal particles interact in the glassy solids. Our very recent results indicate that this colloid chemical reaction method can also be applied to other organic compounds.