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.     

多路Marx并联高压脉冲电源研究

脉冲功率技术在工业和生物医学领域有着广泛的应用,很多应用场合要求输出数百安培的高压脉冲。固态Marx发生器虽已研究多年,但是被广泛采用直插封装的IGBT和MOSFET功率半导体开关管的额定电流通常都低于100 A,无法满足低阻抗负载的应用需求。为提高输出脉冲电流幅值,提出两种多路Marx发生器并联的脉冲电源的拓扑结构,第一种方案采用多路Marx发生器直接并联,第二种是共用一组充电开关管的多路Marx发生器并联。由FPGA提供充放电控制信号,采用串芯磁环隔离驱动方案实现带负压偏置的同步驱动,主电路选用开通速度快、通流能力强的IGBT为主开关的半桥式固态方波Marx电路。实验结果表明,6路16级Marx直接并联的脉冲发生器能输出重频100 Hz高压方波脉冲幅值可达10 kV,在30Ω负载侧输出峰值电流可达300 A,上升时间230 ns。共用充电开关管的6路4级Marx并联发生器在5Ω电阻负载上的输出电流峰值可达300 A,最大输出电流可达460 A,上升时间272 ns。表明多路Marx发生器并联可以有效地减小系统内阻,提高系统带载能力;改进后的并联方案实现大电流脉冲输出的同时,所采用的开关管数量减小近一半,提高了系统的抗干扰能力的同时,降低了脉冲电源的成本;且增加级间并联导线可进一步改善均流效果。     

Taking compact NMR to monitoring real reactions in large-scale chemical industries—General considerations and learnings from a lab-scale test case

The considerations for use of compact nuclear magnetic resonance in a large-scale industrial environment clearly differ from those in academic and educational settings and even from those in smaller companies. In the first part of this article, these differences will be discussed along with the additional requirements that need to be fulfilled for successful applicability in different use cases. In the second part of the article, outcomes from different research activities aiming to fulfill these requirements will be presented with a focus on an online reaction-monitoring study on a lab-scale nucleophilic chlorination reaction.     

Self-Accelerating Diels–Alder Reaction for Preparing Polymers of Intrinsic Microporosity

It is a formidable challenge in polycondensation to simultaneously construct multiple covalent bonds to prepare double-stranded polymers of intrinsic microporosity (PIMs) with fused multicyclic linkages. To the best of our knowledge, this is the first study to develop a self-accelerating Diels–Alder reaction for successfully preparing double-stranded PIMs with fused multicyclic backbone structures. A self-accelerating Diels–Alder reaction was developed based on the [4+2] cycloaddition of sym-dibenzo-1,5-cyclooctadiene-3,7-diyne (DIBOD) and ortho-quinone compounds. In this reaction, the cycloaddition of ortho-quinone with the first alkyne of DIBOD activates the second alkyne, which reacts with ortho-quinone at a rate constant 192 times larger than that of the original alkyne. Using this self-accelerating reaction to polymerize DIBOD and spirocyclic/cyclic difunctional ortho-quinone monomers, a novel stoichiometric imbalance-promoted step-growth polymerization method was developed to prepare PIMs. The resultant PIMs possess intrinsic ultramicropores with pore sizes between 0.45 to 0.7 nm, high specific surface areas above 646 m² g⁻¹, and good H₂ separation performance.     

In Situ Polymerized 1,3-Dioxolane Electrolyte for Integrated Solid-State Lithium Batteries

Solid-state lithium batteries are promising and safe energy storage devices for mobile electronics and electric vehicles. In this work, we report a facile in situ polymerization of 1,3-dioxolane electrolytes to fabricate integrated solid-state lithium batteries. The in situ polymerization and formation of solid-state dioxolane electrolytes on interconnected carbon nanotubes (CNTs) and active materials is the key to realizing a high-performance battery with excellent interfacial contact among CNTs, active materials and electrolytes. Therefore, the electrodes could be tightly integrated into batteries through the CNTs and electrolyte. Electrons/ions enable full access to active materials in the whole electrode. Electrodes with a low resistance of 4.5 Ω □⁻¹ and high lithium-ion diffusion efficiency of 2.5×10⁻¹¹ cm² s⁻¹ can significantly improve the electrochemical kinetics. Subsequently, the batteries demonstrated high energy density, amazing charge/discharge rate and long cycle life.     

Heterophase Photocatalysts from Water‐Soluble Conjugated Polyelectrolytes: An Example of Self‐Initiation under Visible Light

We herein report a new design route to stable, heterophase photocatalysts, which function as highly dispersible conjugated polymer nanoparticles and porous monoliths under visible light in aqueous medium. They were constructed by attachment of the ionic‐liquid species 1‐alkyl‐3‐vinylimidazolium bromide onto the side chains of a photoactive polymer. The structure configuration allows not only photocatalysis in aqueous environment but also a unique self‐initiation radical cross‐linking process to transform the water‐soluble photoactive polymer into a heterophase system, either as nanoparticles or a porous monolith. High photocatalytic activity and reusability of the heterophase system were demonstrated in the degradation of organic dyes and reduction of Cr^VI into Cr^III in water under visible‐light irradiation.     

A Filled‐Honeycomb‐Structured Crystal Formed by Self‐Assembly of a Janus Polyoxometalate–Silsesquioxane (POM–POSS) Co‐Cluster

Clusters with diverse structures and functions have been used to create novel cluster‐assembled materials (CAMs). Understanding their self‐assembly process is a prerequisite to optimize their structure and function. Herein, two kinds of unlike organo‐functionalized inorganic clusters are covalently linked by a short organic tether to form a dumbbell‐shaped Janus co‐cluster. In a mixed solvent of acetonitrile and water, it self‐assembles into a crystal with a honeycomb superstructure constructed by hexagonal close‐packed cylinders of the smaller cluster and an orderly arranged framework of the larger cluster. Reconstruction of these structural features via coarse‐grained molecular simulations demonstrates that the cluster crystallization and the nanoscale phase separation between the two incompatible clusters synergistically result in the unique nano‐architecture. Overall, this work opens up new opportunities for generating novel CAMs for advanced future applications.     

Theoretical Studies of the Reactions CFxH3−xCOOR+Cl and CF3COOCH3+OH

The mechanism and kinetics of the reactions of CF₃COOCH₂CH₃, CF₂HCOOCH₃, and CF₃COOCH₃ with Cl and OH radicals are studied using the B3LYP, MP2, BHandHLYP, and M06‐2X methods with the 6‐311G(d,p) basis set. The study is further refined by using the CCSD(T) and QCISD(T)/6‐311++G(d,p) methods. Seven hydrogen‐abstraction channels are found. All the rate constants, computed by a dual‐level direct method with a small‐curvature tunneling correction, are in good agreement with the experimental data. The tunneling effect is found to be important for the calculated rate constants in the low‐temperature range. For the reaction of CF₃COOCH₂CH₃+Cl, H‐abstraction from the CH₂ group is found to be the dominant reaction channel. The standard enthalpies of formation for the species are also calculated. The Arrhenius expressions are fitted within 200–1000 K as k_T(1)=8.4×10^?20T ^2.63exp(381.28/T), k_T(2)=2.95×10^?21T ^3.13exp(?103.21/T), k_T(3)=1.25×10^?23T ^3.37exp(791.98/T), and k_T(4)=4.53×10^?22T ^3.07exp(465.00/T).