Impact of Positional Isomerism on Pathway Complexity in Aqueous Media

Pathway complexity has become an important topic in recent years due to its relevance in the optimization of molecular assembly processes, which typically require precise sample preparation protocols. Alternatively, competing aggregation pathways can be controlled by molecular design, which primarily rely on geometrical changes of the building blocks. However, understanding how to control pathway complexity by molecular design remains elusive and new approaches are needed. Herein, we exploit positional isomerism as a new molecular design strategy for pathway control in aqueous self‐assembly. We compare the self‐assembly of two carboxyl‐functionalized amphiphilic BODIPY dyes that solely differ in the relative position of functional groups. Placement of the carboxyl group at the 2‐position enables efficient pairwise H‐bonding interactions into a single thermodynamic species, whereas meso‐substitution induces pathway complexity due to competing hydrophobic and hydrogen bonding interactions. Our results show the importance of positional engineering for pathway control in aqueous self‐assembly.     

Synergistic N‐Heterocyclic Carbene/Palladium‐Catalyzed Umpolung 1,4‐Addition of Aryl Iodides to Enals

An umpolung 1,4‐addition of aryl iodides to enals promoted by cooperative (terpy)Pd/NHC catalysis was developed that generates various bioactive β,β‐diaryl propanoate derivatives. This system is not only the first reported palladium‐catalyzed arylation of NHC‐bound homoenolates but also expands the scope of NHC‐induced umpolung transformations. A diverse array of functional groups such as esters, nitriles, alcohols, and heterocycles are tolerated under the mild conditions. This method also circumvents the use of moisture‐sensitive organometallic reagents.     

Palladium-catalyzed regioselective cascade reaction of carbon dioxide,amines and allenes for the synthesis of functionalized carbamates

A palladium-catalyzed regioselective three-component cascade reaction of carbon dioxide,amines and allenes has been developed,providing an expedient and practical method for the construction of a range of functionalized carbamates containing dihydrobenzofuran or indole moiety in moderate to excellent yields.The broad substrate scope,good functional group tolerance and excellent chemo-and regioselectivity are the features of the transformation.     

Finite-time stability of Hadamard fractional differential equations in weighted Banach spaces

Nonlinear Dynamics - The main purpose of this paper is to investigate the finite-time stability of Hadamard fractional differential equations (HFDEs). Firstly, the standard definitions of...     

PDT光敏剂HA在不同液相体系下的光谱特性研究

为了对候选光敏剂竹红菌甲素(HA)进行改性并保持其优异的敏化特性,对HA的光谱特性和激发态性质作了进一步的指认。系统研究了HA在不同液相体系下的吸收和荧光光谱,对指认HA的光谱和电子跃迁的机制提出了新的依据,结果表明,吸收带I产生于π-π*跃迁,吸收带Ⅱ和Ⅲ产生于P-π共轭所导致的L→aπ跃迁的电子振动结构;荧光发射带I和Ⅱ是产生于同一跃迁机制S1(L,aπ)→S0的正常荧光的振动结构。     

电催化氧化制备2,5-呋喃二甲酸

在第75届联合国大会上,我国承诺力争在2030年前实现碳达峰、2060年前实现碳中和。主要由光合作用产生的生物质将在双碳目标中扮演重要角色,通过高效转化可衍生出一系列替代化石产品的高值化学品。其中,2,5-呋喃二甲酸(FDCA)由于具有与石油基对苯二甲酸(TPA)相似的共轭碳环和二酸结构,可替代TPA用于合成热稳定性能、气体阻隔性能更优的生物基呋喃聚酯,大幅降低聚酯行业对化石资源的严重依赖。此外,FDCA在医药、香料、金属配位化学方面也有广泛应用,从而被认为是12种最具潜力的生物基平台化合物之一。FDCA通常可由5-羟甲基糠醛(HMF)通过催化氧化进行合成。相比于需要贵金属催化剂、高温和高压条件、以化学势作为驱动力的传统热催化方法,电催化氧化采用电极电势作为主要驱动力,是更为绿色和高效的新颖合成方法。本综述对电催化氧化制备FDCA反应所用的贵金属、过渡金属和非金属催化剂进行了总结与分析,梳理了催化剂设计和反应机理的研究脉络,并指出了该领域发展所面临的挑战与机遇。     

基于Khimera软件的Se和Sn氧化动力学参数计算

反应速率常数和指前因子、活化能等动力学参数的准确性是研究痕量元素动力学模型的关键,在Se和Sn氧化过程的反应机理研究基础上,借助于量化软件Gaussview和Gaussian及动力学软件Khimera,采用量子化学从头计算理论对Se和Sn氧化过程进行研究,最终得到了在200~2000K温度区间内的反应速率k随温度T变化的关系,进一步计算了Arrhenius参数,得出了活化能随温度变化的关系,弥补了以往只能计算单个温度点的化学反应速率值的不足,为深入研究煤燃烧过程中Se和Sn的生成与排放的动力学模型提供了依据。     

Highly stable aqueous rechargeable Zn-ion battery: The synergistic effect between NaV_6O_(15) and V_2O_5 in skin-core heterostructured nanowires cathode

The aqueous rechargeable Zn-ion batteries based on the safe,low cost and environmental benignity aqueous electrolytes are one of the most compelling candidates for large scale energy storage applications.However,pursuing suitable insertion materials may be a great challenge due to the strong electrostatic interaction between Zn^{^(2+})and cathode materials.Hence,a novel NaV₆O₁₅/V₂O₅ skin-core heterostructure nanowire is reported via a one-step hydrothermal method and subsequent calcination for high-stable aqueous Zn-ion batteries(ZIBs).The NaV₆O₁₅/V₂O₅ cathode delivers high specific capacity of 390 m Ah/g at 0.3 A/g and outstanding cycling stability of 267 m Ah/g at 5 A/g with high capacity retention over 92.3%after 3000 cycles.The superior electrochemical performances are attributed to the synergistic effect of skin-core heterostructured NaV₆O₁₅/V₂O₅,in which the sheath of NaV₆O₁₅ possesses high stability and conductivity,and the V₂O₅ endows high specific capacity.Besides,the heterojunction structure not only accelerates intercalation kinetics of Zn²⁺transport but also further consolidates the stability of the layers of V₂O₅ during the cyclic process.This work provides a new perspective in developing feasible insertion materials for rechargeable aqueous ZIBs.     

基于三维简并四波混频的PDT光敏剂HA瞬态光栅特性研究

竹红菌甲素(hypocrellin A,HA)具有丰富的激发态特性,有可能在新型光动力疗法(PDT)光敏剂、激光染料和新型光电器件方面有一定的应用前景。利用瞬态光栅技术研究了竹红菌甲素分别在不同极性和粘度溶剂中以及溶剂本身的瞬态光栅特性,把其瞬态光栅的超快过程归结为竹红菌甲素质子转移形成的过渡态TS*的衰减,得出过渡态TS*瞬态光栅的寿命为10.5 ps。竹红菌甲素分子的质子转移过渡态TS*瞬态光栅寿命不受溶剂极性和粘度的影响。     

Synthesis and thermal energy storage properties of the polyurethane solid–solid phase change materials with a novel tetrahydroxy compound

Based on the phase change theory, a novel tetrahydroxy compound (THCD) was designed and prepared. Depending on the spatial structure of the tetrahydroxy compound, a form-stable thermoplastic polyurethane solid–solid phase change material (TPUPCM) was synthesized via employing PEG as soft segments, while multi-benzene ring structure made by 4,4′-diphenylmethane diisocyanate and tetrahydroxy compound as hard segments. The composition and structure of THCD and TPUPCM, the TPUPCM’s the weight average molecular weight and number average molecular weight, dissolving and melting abilities, phase change behaviors, thermal performances and crystalline morphology were investigated by Fourier transform infrared spectrometer, ¹H nuclear magnetic resonance spectrometer, multiangle laser light scattering apparatus, differential scanning calorimentry, dynamic mechanical thermal analysis, thermogravimetry analysis system, wide-angle X-ray diffraction, polarizing optical microscopy. The results show that the solid–solid phase change material owns excellent phase change properties and a broad processing temperature range. The heating cycle phase change enthalpy is 137.4 J/g, and the cooling cycle phase change enthalpy is 127.6 J/g. The started decomposition temperature and the maximum decomposition temperature are at 323.5 and 396.2 °C, respectively. Furthermore, the solid–solid phase change material is dissolvable, meltable and can be processed directly, and has great potential applications in thermal energy storage.