检测痕量纳米金的纳米催化光度法

在EDTA—NaOH介质中,金纳米微粒对盐酸联氨还原硫酸铜生成铜微粒这一慢反应具有较强的催化作用．铜微粒在750nm处产生一个吸收峰．随着纳米金浓度的增大,750nm处的吸光强度线性增大．对于粒径为10、30、50nm的纳米金,其线性范围、回归方程、检出限分别为0．12～1．68、0．36～2．80、1．00～5．00nmol／L,△A750nm=0．3205CAu＋0．0076、△A750nm=0．2201CAu＋0．0056、△A750nm=0．1150CAu＋0．0066,0．05、0．20、0．50nmol／L Au．分别对0．50、1．00nmol／L纳米金（d=10nm）平行测定10次,求得其相对标准偏差分别为4．2％、3．5％．     

meso—四（4—磺基苯基）卟啉双波长分光光度法测定阳离子表面活性剂

在酸性条件下，阳离子表面活性剂使ｍｅｓｏ－四（４－磺基苯基）卟啉（ＴＰＰＳ４）发生Ｊ－型聚合，在４９０ｎｍ处出现Ｊ－型聚集吸收并导致位于４３４ｎｍ的Ｓｏｒｅｔ吸收带降低。阴离子表面活性剂如十二烷基硫酸钠（ＳＤＳ）使聚集更一步增强，据此建立起水中痕量阳离子表面活性剂的双波长分光光度测定，方法成功地应用于合成和实际水样分析。     

Stabilizing a Platinum1 Single‐Atom Catalyst on Supported Phosphomolybdic Acid without Compromising Hydrogenation Activity

In coordination chemistry, catalytically active metal complexes in a zero‐ or low‐valent state often adopt four‐coordinate square‐planar or tetrahedral geometry. By applying this principle, we have developed a stable Pt₁ single‐atom catalyst with a high Pt loading (close to 1 wt %) on phosphomolybdic acid(PMA)‐modified active carbon. This was achieved by anchoring Pt on the four‐fold hollow sites on PMA. Each Pt atom is stabilized by four oxygen atoms in a distorted square‐planar geometry, with Pt slightly protruding from the oxygen planar surface. Pt is positively charged, absorbs hydrogen easily, and exhibits excellent performance in the hydrogenation of nitrobenzene and cyclohexanone. It is likely that the system described here can be extended to a number of stable SACs with superior catalytic activities.     

阴离子Gemini表面活性剂和阳离子传统表面活性剂混合体系双水相中囊泡形貌的转变

通过电子显微镜观察了阴离子gemini表面活性剂C₁₁- p-PhCNa和阳离子传统表面活性剂DTAB混合体系双水相中囊泡形貌随体系组成和浓度的转变。结果表明,双水相较浓的一相中形成了多层囊泡,囊泡的大小和壁厚随相的组成和浓度而改变,两组分等电荷混合有利于形成较大且壁较厚的囊泡。分析表明, gemini表面活性剂在聚集体中采取的反式构象可能是其容易形成厚壁多层囊泡的重要原因,C₁₁- p-PhCNa联接链上的苯氧基与DTA⁺之间的p-阳离子相互作用以及两组分相反电性头基之间的静电吸引使囊泡壁的多层结构更加稳定。     

Enhancing Temporal Control and Enabling Chain‐End Modification in Photoregulated Cationic Polymerizations by Using Iridium‐Based Catalysts

Gaining temporal control over chain growth is a key challenge in the enhancement of controlled living polymerizations. Though research on photocontrolled polymerizations is still in its infancy, it has already proven useful in the development of previously inaccessible materials. Photocontrol has now been extended to cationic polymerizations using 2,4,6‐triarylpyrylium salts as photocatalysts. Despite the ability to stop polymerization for a short time, monomer conversion was observed over long dark periods. Improved catalyst systems based on Ir complexes give optimal temporal control over chain growth. The excellent stability of these complexes and the ability to tune the excited and ground state redox potentials to regulate the number of monomer additions per cation formed allows polymerization to be halted for more than 20 hours. The excellent stability of these iridium catalysts in the presence of more nucleophilic species enables chain‐end functionalization of these polymers.     

New Ion‐Pair Based All‐Solid‐State Surfactant Sensitive Sensor for Potentiometric Determination of Cationic Surfactants

Cationic surfactants of different types were determined using a few potentiometric sensors based on ion‐pair complexes (dodecyldimethylbenzylammonium dodecylsulfate, dodecylmethylbenzylammonium dodecylbenzensulfonate, tetrahexadecylammonium dodecylsulfate and Hyamine (benzethonium dodecylsulfate)) as sensing materials. The response of the all‐solid state surfactant sensitive electrode based on a Teflonized graphite conducting substrate, coated with a PVC membrane containing sensing material, was investigated in the solutions of Hyamine and hexadecyltrimethylammonium ion in the concentration range from 1 μM to 10 mM. Potentiometric surfactant cation titration has been performed using sodium dodecylsulfate as titrant and an ion‐pair‐based surfactant sensitive electrode as a potentiometric indicator. Several commercial surfactant products have also been titrated and the results were compared with those obtained with two‐phase standard titration method.     

Interaction of Plasma Proteins with Tri‐quaternary Ammonium Salt Cationic Surfactant Studied by QCM‐D

A tri‐quaternary ammonium salt cationic surfactant was synthesized. Its structure was confirmed by using Fourier‐transform infrared spectroscopy, ¹H nuclear magnetic resonance spectroscopy, and X‐ray photoelectron spectroscopy analyses. Three model surfaces, including Au‐CH₃, Au‐OH and Au‐COOH, were fabricated. Adsorptions of surfactant on the three model surfaces and subsequent plasma proteins adsorption were investigated by quartz crystal microbalance with dissipation (QCM‐D). The mass of surfactant on the Au‐COOH surface was the largest, followed by that on the Au‐CH₃ surface, and that on the Au‐OH surface. These results suggested that the main driving force of surfactant immobilization was electrostatic interaction followed by hydrophobic interaction. Based on the results obtained, we concluded that the protein mass adsorbed on Au‐CH₃‐ S , Au‐OH‐ S , and Au‐COOH‐ S surfaces depended on the protein size and orientation. The mass and thickness of S on the Au‐COOH surface is the largest and the protein adsorption capacity of Au‐COOH‐ S surface is inferior to that of Au‐CH₃‐ S . The Au‐COOH‐ S surface could inhibit lysozyme adsorption, maintain the adsorption balance of bovine serum albumin, and induce fibrinogen‐binding protein adsorption.     

Metal‐Organic Frameworks as Platform for Lewis‐Acid‐Catalyzed Organic Transformations

Metal‐organic frameworks (MOFs) are highly promising Lewis acid catalysts; they either inherently possess Lewis acid sites (LASs) on it or the LASs can be generated through various post‐synthetic methods, the later can be performed in MOFs in a trivial fashion. MOFs are suitable platform for catalysis because of its highly crystalline and porous nature. Moreover, with recent advancements, thermal and chemical stability is not a problem with many MOFs. In this Minireview, an enormous versatility of MOFs, in terms of their microporosity/mesoporosity, size/shape selectivity, chirality, pore size, etc., has been highlighted. These are advantageous for designing and performing various targeted organic transformations. Although, many organic transformations catalyzed by MOFs with LASs have been reported in the recent past. In this Minireview, we have restricted ourselves to four important organic reactions: (i) cyanosilylation, (ii) Diels–Alder reaction, (iii) C?H activation, and (iv) CO₂‐addition. The discussion focuses mostly on the recent reports (42 examples).     

A New Method for The UV Spectrophotometric Determination of Mercury

Abstract

Mercury forms a complex with 2-mercaptobenzoic acid which may be extracted into ethyl acetate to form the basis of a selective and sensitive method for the determination of mercury by solution spectrophotometry at 265 nm. Of twenty-nine ions investigated, only Cu²⁺, Co²⁺, Zn²⁺ and Fe³⁺ interfered at 100-fold molar excess.     

Controlled Cationic Polymerization of 1‐Methoxy‐1,3‐Butadiene: Long‐Lived Species‐Mediated Reaction and Control over Microstructure with Weak Lewis Bases

Controlled cationic polymerization of trans‐1‐methoxy‐1,3‐butadiene was achieved through the design of appropriate initiating systems, yielding soluble polymers with controllable molecular weights. The combined use of SnCl₄ or GaCl₃ as a Lewis acid catalyst and a weak Lewis base in conjunction with HCl as a protonogen resulted in efficient and controlled polymerization. The M_n values of the product polymers increased linearly along the theoretical line, which indicates that intermolecular crosslinking reactions negligibly occurred. In addition, the polymer microstructure was critically dependent on the weak Lewis base employed. In particular, the use of tetrahydrofuran as an additive resulted in the highest 4,1/4,3‐structure ratio (96/4). Weak Lewis bases also affected the polymerization rates but exhibited unique trends that differed from their effects on the cationic polymerization of alkyl vinyl ethers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 288–296     

Selective Formic Acid Decomposition for High‐Pressure Hydrogen Generation: A Mechanistic Study

A viable storage system for hydrogen based on selective formic acid decomposition into H₂ and CO₂ has been developed (see scheme). Continuous generation of H₂ of very high purity, over a wide range of pressures and under mild conditions was achieved.

     

High‐Throughput Reaction Optimisation and Activity Screening of Ferrocene‐Based Lewis Acid–Catalyst Complexes by Using Continuous‐Flow Reaction Detection Mass Spectrometry

Optimising synthetic conversions and assessing catalyst performance is a tedious and laborious endeavour. Herein, we present an automated alternative to the commonly applied sequential approaches that are used to increase catalyst discovery process efficiencies by increasing the number of entities that can be tested. This new approach combines conversion of the reactants and determination of product formation into a single comprehensive reaction detection system that can be operated with minimal catalyst and reactant consumption. With this approach, rudimentary reaction conditions can be quickly optimised and the same system can then be used to screen for the optimal homogenous catalyst in a selected solution‐phase synthetic conversion. The system, which is composed of standard HPLC components, can be used to screen catalyst libraries at a repetition rate of five minutes and can be run unsupervised. The sensitive mass spectrometric detection that is implemented in the reaction detection methodology can be used for the simultaneous monitoring of reactants, catalysts and product ions. In the experiments, the three‐component reaction that gives a substituted 2‐imidazoline was optimised. Afterwards, the same method was used to assess a library of ferrocene‐based Lewis acid catalysts for performance in the aforementioned conversion in six different solvents. We demonstrate the feasibility of using this methodology to directly compare the performance results obtained in different solvents by calibrating the solvent‐specific MS responses.     

以金属离子为增稳剂的酶法终点法测定MPT- NAG含量

建立了快速、简便、灵敏地测定MPT - NAG含量的酶法终点法.以金属离子为增稳剂,N-乙酰-β-D-氨基葡萄糖苷酶(NAG)催化6-甲基-2-硫代吡啶-N-乙酰-β-D-氨基葡萄糖苷(MPT - NAG)水解,生成产物6-甲基-2巯基吡啶(MPT),MPT在340 nm处有吸收峰,通过测定340 nm处吸光度值计算M...     

New High‐Power LEDs Open Photochemistry for Near‐Infrared‐Sensitized Radical and Cationic Photopolymerization

Cyanines derived from heptamethines were investigated in combination with iodonium salts as initiators of the radical polymerization of tripropylene glycol diacrylate and epoxides derived from bisphenol‐A‐diglycidylether. A new near‐infrared (NIR) LED prototype emitting at 805 nm with an exposure intensity of 1.2 W cm^?2 facilitated initiation of both radical and cationic polymerization using sensitizers derived from cyanines. This new light‐emitting device has brought new insight into the photochemistry of cyanines with the general structure 1 because a combination of photonic and thermal processes strongly influences reaction pathways. In particular, cationic cyanines comprising a cyclopentene moiety and diphenylamino group in the center initiated the cationic polymerization of epoxides. Selective oxidation of this unit explains why specifically these derivatives may function as initiators for cationic polymerization. In contrast, when the diphenylamino group was replaced by a barbital group at the meso‐position cationic polymerization of epoxides was not initiated.     

A Diazido Mannose Analogue as a Chemoenzymatic Synthon for Synthesizing Di‐N‐acetyllegionaminic Acid‐Containing Glycosides

A chemoenzymatic synthon was designed to expand the scope of the chemoenzymatic synthesis of carbohydrates. The synthon was enzymatically converted into carbohydrate analogues, which were readily derivatized chemically to produce the desired targets. The strategy is demonstrated for the synthesis of glycosides containing 7,9‐di‐N‐acetyllegionaminic acid (Leg5,7Ac₂), a bacterial nonulosonic acid (NulO) analogue of sialic acid. A versatile library of α2‐3/6‐linked Leg5,7Ac₂‐glycosides was built by using chemically synthesized 2,4‐diazido‐2,4,6‐trideoxymannose as a chemoenzymatic synthon for highly efficient one‐pot multienzyme (OPME) sialylation followed by downstream chemical conversion of the azido groups into acetamido groups. The syntheses required 10 steps from commercially available d ‐fucose and had an overall yield of 34–52 %, thus representing a significant improvement over previous methods. Free Leg5,7Ac₂ monosaccharide was also synthesized by a sialic acid aldolase‐catalyzed reaction.     

Study of Spectrophotometric Characteristics of the Charge Transfer Reaction of Aminomethylbenzoic Acid with 7,7,8,8‐Tetracyanoquinodimethane

A new spectrophotometric method was developed for the determination of aminomethylbenzoic acid (PAMBA) using 7,7,8,8‐tetracyanoquinodimethane (TCNQ). The method was based on the formation of charge transfer (CT) complex of this drug as n‐electron donor with the π‐acceptor TCNQ. TCNQ was found to react with PAMBA to produce a kind of yellow complex. The CT reaction proceeded quantitatively in pH 8.5 buffer solution. Different variables affecting the reaction were carefully studied and optimized. Under optimal reaction conditions, the stoichiometric ratio of the reaction, maximum absorption wavelength and the value of molar absorptivity were measured to be 1:1, 425 nm, and 1.9×10⁴ L·mol^?1·cm^?1, respectively. Beer′s law was obeyed in the range of 1–9 µg·mL^?1 of PAMBA. The data have been filled to a linear regression equation A=?0.2612+0.1123c (µg·mL^?1), with a correlation coefficient of 0.9996. The detection limit was 0.4 µg·mL^?1, R.S.D. was less than 1.9%, and average recovery was over 97.6%. The formation of the CT complex was also confirmed by both infrared and ¹H NMR measurements. The thermodynamic property, kinetic property and reaction mechanism have also been discussed. The method developed was applied successfully to the determination of the subject drug in its pharmaceutical dosage forms with good precision and accuracy compared to official method revealed by t‐ and F‐tests.     

金属离子增稳的酶法终点法测定1,5-脱水葡糖醇

为建立金属离子增稳的酶法终点法测定1,5-脱水葡糖醇,通过葡萄糖激酶(GK)和葡萄糖-6-磷酸脱氢酶(G6PD)将样品中葡萄糖(Glu)转化为6-磷酸葡萄糖内酯(G6PL),1,5-AG经吡喃糖氧化酶(PROD)作用生成1,5-脱水果糖(1,5-AF)和H2O2,后者借Trinder’s系统显色定量。结果表明,该法线性范围0～250μmol/L,平均回收率为99.3%,批内变异系数(CV)和批间变异系数分别为0.009 8～0.027 7、0.016 2～0.036 8,与气相色谱-质谱法(GC-MS)比较具有良好的相关性,线性回归方程和相关系数分别为y=0.982 x+2.68,r=0.998 8。以金属离子为增稳剂的酶法终点法测定1,5-AG含量具有简便、灵敏、可靠的特点,适合实际推广应用。     

以铁的催化褪色新指示反应测定超痕量铁

本文研究了在乙酸介质中,铁(Ⅲ)催化过氧化氢氧化钙试剂羧酸钠盐的褪色反应,利用这个反应建立了超痕量铁测定的新方法。本方法的桑德尔灵敏度为2.92×10^-5μg/cm²,是目前铁的光度测定中灵敏度最高的方法之一。本方法已成功地用于饮用水、若干品种粮食和人发中超痕量铁的测定。     

Recent Developments in the Chiral Brønsted Acid‐catalyzed Allylboration Reaction with Polyfunctionalized Substrates

Asymmetric allylboration has played a central role in organic synthesis ever since the pioneering work by Hoffman and Brown, having found applications in the total synthesis of many natural products. A new dawn for this 40 year‐old reaction occurred with the beginning of the new century when the first catalytic asymmetric methods came into play. In less than one decade, several methodologies, able to achieve the desired homoallylic alcohols with ee ranges in the high 90s, were developed. Among them, in the present account, we will disclose our contribution to the development of the chiral binolphosphoric‐derived Brønsted acid‐catalyzed allylboration of aldehydes originally reported by Antilla in 2010. Our contribution to this field lies in its application to polyfunctionalized systems, both on the aldehyde and the allylboronate in question, which enables the rapid construction of molecular diversity and complexity. Parts of the work described herein have been carried out in collaboration with the groups of Profs. Akiyama and Houk.