Potentiometric studies on the complexes of some trivalent rare earths with 5-chloropyridine-2,3-diol

The complexes of some rare earths [Ce(III), Pr(III), Nd(III), Sm(III), Tb(III), Dy(III), and Ho(III)] with 5-chloropyridine-2,3-diol (CPD) were studied potentiometrically in 50% dioxane-water at a ionic strength of 0.1M (NaClO₄) at 35±0.1 °C. The proton-ligand stability constant ofCPD and the stability constants of its complexes with the metals have been determined using theCalvin-Bjerrum technique as modified byIrving andRossotti. The order of the stability constants is found to be Ce < Pr < Nd < Sm < Tb < Dy < Ho.

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Potentiometrische Untersuchungen der Komplexe einiger trivalenter Seltenerdmetalle mit 5-Chlorpyridin-2,3-diol

Zusammenfassung Es wurden die Komplexe von Ce(III), Pr(III), Nd(III), Sm(III), Tb(III), Dy(III) und Ho(III) mit 5-Chlorpyridin-2,3-diol (CPD) in 50% Dioxan-Wasser bei einer Ionenstärke von 0,1M (NaClO₄) und einer Temperatur von 35±0,1 °C potentiometrisch untersucht. Die Proton-Ligand-Stabilitätskonstante vonCPD und die Stabilitätskonstanten der Metallkomplexe wurden nach der Methode vonCalvin-Bjerrum mit derIrving-Rossotti-Modifikation bestimmt. Die Reihenfolge der Stabilitätskonstanten ergab sich folgendermaßen: Ce < Pr < Nd < Sm < Tb < Dy < Ho.

     

Multiple-wavelength data treatment of ultraviolet—visible spectra for 1:1 electron donor—acceptor adducts of p-nitrophenol in heptane

The absorbances of solutions of p-nitrophenol and an electron donor in heptane are measured at 298 K over 240–400 nm at 1-nm intervals. The data are treated by a personal computer; on each spectrum, the differences between the measured absorbance and the absorbance calculated from an assumed formation constant are accumulated over the whole wavelength region, and divided by a normalizing factor which is obtained from the area under the measured spectrum. The optimal values of the constant for each spectrum are then averaged. The 1:1 adduct formation constants, log K_as, were 2.22 ± 0.17 for 4-methyl-2-pentanone, 3.95 ± 0.06 for N,N-dimethylacetamide, and 5.55 ± 0.13 for trioctylphosphine oxide. The method is applicable for various systems with this kind of equilibrium and has advantages over least-squares procedures.     

Cascade Reactions in Quantitative Solid-State Syntheses

100 % yield in the absence of the liquid phase : A one-pot synthesis of highly substituted pyrroles, which proceeds in solution with moderate yields, functions quantitatively in the solid–solid variant, and that at much lower temperatures, although at least four reaction steps are required. The reaction execution in the absence of liquid phases avoids product workup because of the 100 % yield and is thus resource-saving and environmentally friendly.     

有机农药异丙隆的级联生物降解体系的构建

构建了一个酶促氧化结合活性淤泥处理的级联生物降解有机农药异丙隆的体系.首先,建立了氯过氧化物酶（CPO）催化H₂O₂氧化降解异丙隆的酶处理体系.在最佳反应条件下,异丙隆的降解率可在10 min内达到100%.反应在室温下进行,pH=3.0,所需H₂O₂浓度为0.2 mmol/L,酶用量极少,仅7 nmol/L.降解体系高效、温和、绿色,无二次污染,极具应用潜力.CPO酶促氧化降解异丙隆的产物用HPLC-MS测定,并进一步根据主要产物推测了降解的途径.结果表明,异丙隆经CPO催化H₂O₂氧化处理后,被分解成较小的4-异丙基苯胺和4-乙基苯胺苄基正离子碎片分子.如果将CPO-H₂O₂酶促氧化作为一种前处理手段,后续与活性淤泥微生物降解过程结合,通过这种二级处理方法可实现含异丙隆污水的化学需氧量（COD）的有效去除,达到含异丙隆污水深度治理的目的.进一步以绿藻Chlorella pyrenoidosa的生长抑制率为评价指标对异丙隆酶催化氧化降解的产物进行了毒性评估,结果表明,随着底物降解率的逐渐增大,降解产物对绿藻的生长抑制率逐渐减小,说明经酶法降解后得到的产物与异丙隆相比毒性降低.     

Thermodynamic studies of alkaline-earth-metal cation complexation by lipophilic dioxa,trioxa, and dithia dicarboxylic acids

Five new lipophilic dicarboxylic acids with systematic structural variation in the bridge which joins the two lipophilic carboxylic acid units have been synthesized. Potentiometric equilibrium measurements of hydrogen ion concentrations have been employed to determine the protonation constants for these lipophilic di-ionizable acyclic ligands in 90% methanol-10% water (v/v) at 25.0 °C and an ionic strength of 0.10 M and the stability constants for their complexes with Mg²⁺, Ca²⁺, and Sr²⁺. Although all five ligands exhibit the highest stability constants for Ca²⁺, the magnitude of the differences between the stability constants for complexation of Ca²⁺ versus Mg²⁺ or Sr²⁺ is found to vary widely depending upon the identity of the bridging unit which joins the two carboxylic acid end groups.     

铁氨基黏土-葡萄糖氧化酶纳米复合催化剂的构筑及多酶级联反应研究

以铁氨基黏土(FeAC)为载体, 通过共价交联固定葡萄糖氧化酶(GO_x), 构筑了铁氨基黏土-葡萄糖氧化酶纳米复合催化剂(FeAC-GO_x). 利用FeAC的过氧化物酶活性, 与GO_x结合进行级联反应, 可催化葡萄糖转化为过氧化氢并产生显色反应; 采用扫描电子显微镜(SEM)、 X射线衍射(XRD)和傅里叶变换红外光谱(FTIR)对FeAC-GO_x进行了形貌和结构表征, 并评价了其酶动力学参数、 催化稳定性和重复使用性等. 结果表明, GO_x的固定化率可达到76.4%, 所构筑的纳米结构酶复合体系具有高效的级联催化能力. 与天然酶体系相比, FeAC-GO_x具有更优异的温度和pH耐受性, 且在重复使用6次后, 酶催化活性无明显降低. 该体系不仅为新型葡萄糖传感器的开发奠定了基础, 还为多酶级联纳米结构酶的构筑提供了新思路.     

Reflections on the calculation and publication of potentiometrically-determined formation constants

Calculation and reporting procedures are described, which aim to improve the quality and comparability of published formation constant values obtained by glass-electrode potentiometry. Ways in which the processing of data by computer optimization programs can be standardized are the main concern, particularly in respect of improving the usefulness of equilibrium data through incorporation into large publically available databases. These recommendations may be particularly valuable to researchers beginning in this field as well as to those who determine formation constants only occasionally.     

Iminium Ion Cascade Reactions: Stereoselective Synthesis of Quinolizidines and Indolizidines

A novel iminium ion cascade reaction has been developed that allows for the stereoselective synthesis of a variety of substituted aza-fused bicycles. The combination of amino allylsilanes and aldehydes (or ketones) was used to synthesize a number of quinolizidines and indolizidines in a one-pot reaction sequence. This technology has been used to effect the facile syntheses of several indolizidine and quinolizidine natural products including (±)-epilupinine, (±)-tashiromine, and (−)-epimyrtine. Substrate scope has been examined varying the type of amino allylsilanes (primary, secondary, and conjugated) and carbonyl compounds (aldehydes and ketones) to give a variety of fused ring structures. Varying the components chosen allows for the inclusion of synthetically useful functional groups at different positions on the core structure. The methodology has been used to construct the tricyclic core structures present in the cylindricine family and halichlorine.     

半胱胺-Zn(Ⅱ)络合反应稳定性及热力学特征研究

采用pH电位滴定法,于温度25℃条件下,获取半胱胺盐酸盐的各级加质子常数(lgK_1~H=10.92,lgK_2~H=8.25)、离解常数(K_(a1)=5.62E-09,K_(a2)=1.20E-11)及其与Zn(Ⅱ)形成配合物的稳定常数(lgk5=36.74)、热力学函数(△rHm=-157.14kJ/mol,△rSm=176.74J/(mol·K),△_rGm=-209.60kJ/mol),并计算各pH条件下半胱胺盐酸盐与Zn(Ⅱ)配合的条件稳定常数。计算得Zn(Ⅱ)与半胱胺盐酸盐配位反应的热力学函数△rGm0、△rHm0、△rSm0,证明反应过程为自发放热。半胱胺盐酸盐与Zn(Ⅱ)形成配合物的稳定常数和条件稳定常数均很大,表明形成的半胱胺锌很稳定。     

Enzyme-Polymer-Conjugate-Based Pickering Emulsions for Cell-Free Expression and Cascade Biotransformation

In this study, we addressed the limitations of conventional enzyme-polymer-conjugate-based Pickering emulsions for interfacial biocatalysis, which traditionally suffer from nonspecific and uncontrollable conjugation positions that can impede catalytic performance. By introducing a non-canonical amino acid (ncAA) at a specific site on target enzymes, we enabled precise polymer-enzyme conjugation. These engineered conjugates then acted as biocatalytically active emulsifiers to stabilize Pickering emulsions, while encapsulating a cell-free protein synthesis (CFPS) system in the aqueous phase for targeted enzyme expression. The resulting cascade reaction system leveraged enzymes expressed in the aqueous phase and on the emulsion interface for optimized chemical biosynthesis. The use of the cell-free system eliminated the need for intact whole cells or purified enzymes, representing a significant advancement in biocatalysis. Remarkably, the integration of Pickering emulsion, precise enzyme-polymer conjugation, and CFPS resulted in a fivefold enhancement in catalytic performance as compared to traditional single-phase reactions. Therefore, our approach harnesses the combined strengths of advanced biochemical engineering techniques, offering an efficient and practical solution for the synthesis of value-added chemicals in various biocatalysis and biotransformation applications.     

一种求算三元络合物稳定常数的新方法

一种求算三元络合物稳定常数的新方法主沉浮魏云鹤林秀丽张长桥（山东工业大学数理系济南２５００６１）关键词三元配合物稳定常数中图分类号Ｏ６４１．４１．引言一种金属离子与一种有色配体形成二元有色配合物后，若体系中有另一种无色配体存在，则会进一步形成有色三元...     

新型酰胺金属配合物的热力学稳定性研究

酰胺在自然界中广泛存在,生物体内很多金属酶中的酰胺都参与了金属配位,文献表明,配位的金属离子可以促进酰胺的去质子化,去质子后的酰胺氮原子是一种良好的电子授体,当前对酰胺配体的研究已有报道,为模拟抗癌药物博莱霉素,Rowland等合成了一个新型五齿酰胺配体：N,N-双(2-吡啶甲基)胺-N-乙基-2-吡啶-2-甲酰胺(L),并对其三价铁配合物的单晶结构进行了表征,实验证明此配体在配合物中的配位环境和化学性质与博莱霉素非常相似。     

Cascade synthesis of substituted 4-amino-1,2,4-triazol-3-ones from aldehyde hydrazones and azodicarboxylates

Substituted 4-amino-1,2,4-triazol-3-ones were synthesized from aldehyde hydrazones and azodicarboxylates in the presence of triphenylphosphine. The cascade reaction was conducted in a single step and the procedure is general and efficient.     

A Liquid-Liquid-Solid System to Manipulate the Cascade Reaction for Highly Selective Electrosynthesis of Aldehyde

Electrocatalytic synthesis of aldehydes from alcohols exhibits unique superiorities as a promising technology, in which cascade reactions are involved. However, the cascade reactions are severely limited by the low selectivity resulting from the peroxidation of aldehydes in a traditional liquid-solid system. Herein, we report a novel liquid-liquid-solid system to regulate the selectivity of benzyl alcohol electrooxidation. The selectivity of benzaldehyde increases 200-fold from 0.4 % to 80.4 % compared with the liquid-solid system at a high current density of 136 mA cm⁻², which is the highest one up to date. In the tri-phase system, the benzaldehyde peroxidation is suppressed efficiently, with the conversion of benzaldehyde being decreased from 87.6 % to 3.8 %. The as-produced benzaldehyde can be in situ extracted to toluene phase and separated from the electrolyte to get purified benzaldehyde. This strategy provides an efficient way to efficiently enhance the selectivity of electrocatalytic cascade reactions.     

Cascade reactions of 1,2,4-triazines: direct thermochemical access to functionalized 4,5-dihydroazocines

A rapid, facile approach to functionalized 4,5-dihydroazocines has been developed, exploiting a one-pot reaction cascade from easily-prepared 3-(ethoxycarbonyl)-5-phenyl-1,2,4-triazine, cyclobutanone and secondary amines.     

Cascade synthesis of benzofuran derivatives via laccase oxidation-Michael addition

The cascade synthesis of benzofuran derivatives was conducted from the reaction of catechols and 1,3-dicarbonyl compounds via oxidation-Michael addition in the presence of laccase and Sc(OTf)₃/SDS. This reaction was carried out under air at room temperature in aqueous medium, and provided benzofuran products in moderate to good yields. In addition, this reaction system showed recyclability.     

Determination of individual stability constants of coexisting molecular complexes formed by unresolvable isomers

Some biogenic substances undergo steric isomerism or tautomerism in which the isomers are unresolvable. Naturally, the isomers are expected to form molecular complexes with distinct stabilities. This paper proposes the method of determining individually the stability constants of complexes formed under isomerisation and complexation equilibria: the NMR titration curves are modelled and formulated for fast and slow isomeric equilibria, the process of least-squares fittings is explained, and the application to supramolecular complexation of unresolvable isomers is discussed as compared with NMR titration data reported for α- and β-D-glucosamine anomers.     

4-Dimethylaminopyridine-catalyzed Cascade Reaction for Efficient Synthesis of Naphthofurans

A convenient and efficient method was developed for the synthesis of naphtho[2,1-b]furans via 4-dimethylaminopyridine(DMAP)-catalyzed cascade reaction of 2-hydroxy-1-naphthaldehydes and α-halogenated ketones in moderate to good yields in the presence of Na₂CO₃ at 80℃ for 6 h. The mechanism for this process was briefly discussed with a tentative catalytic cycle proposed. Moreover, this method features organocatalysts and high step-economy, which makes it practical and attractive.     

一种新型磁天平在配合物磁化率测定中的应用

经典物理化学实验"磁化率测定实验"中,传统方法是使用Gouy磁天平,仪器笨重且操作复杂。本文提供一种新型台式磁天平,用于配合物磁化率的测定。文中通过测量三种亚铁化合物的磁化率,介绍该磁天平的基本原理、使用方法、操作步骤和数据分析。通过比较测量值和标准值,得出该仪器的测量误差小、精确度高,适用于实验教学和科学研究。     

Polarographic Eiectroreduction of Some Complexes of Uranium with Macrocyclic Polyethers

Abstract

The polarographic behaviour of uranium(VI) in aqueous C. 1 N nitric acid medium, in the presence of some polyoxa macrocyclic ligands (15-crown-5, benzo-15-crown-5, 18-crown-6, dicyclohexyl-18-crown-6), at 25°C, was investigated. Both in the absence and in the presence of the polyoxa macrocyclic ligands, the reduction of hexavalent uranium in aqueous medium takes place in two steps, each of which involving the transfer of an electron. Under diffusion-controlled conditions, the two steps of the reduction in acid medium proceed reversibly. The results of the polarographic measurements enabled to estimate the ratio of the stability constants of the complex ions of U(111) and of U(IV) with macrocyclic polyethers.