Simultaneous accumulation of both skeletal and appendage-based diversities on tandem Ugi/Diels-Alder products

Diversity-oriented organic synthesis (DOS) is a key concept for construction of skeletally diverse small molecule libraries to discover drug-like small molecules. Here, we describe a DOS class to transform a complex 7-oxanorbornene skeleton, which is readily accessible by a tandem Ugi/Diels-Alder reaction, into two heterotricycle skeletons selectively by using tandem ROM/CM/RCM reaction. In the present study, the mode of cyclization is pre-encoded by building blocks used in the complexity-generating tandem Ugi/Diels-Alder reaction. Since variable alkenes can be used in the CM reaction, our approach can be extended to construct both skeleton- and appendage-diverse small molecule libraries.     

A Biocompatible Alkene Hydrogenation Merges Organic Synthesis with Microbial Metabolism

Organic chemists and metabolic engineers use orthogonal technologies to construct essential small molecules such as pharmaceuticals and commodity chemicals. While chemists have leveraged the unique capabilities of biological catalysts for small‐molecule production, metabolic engineers have not likewise integrated reactions from organic synthesis with the metabolism of living organisms. Reported herein is a method for alkene hydrogenation which utilizes a palladium catalyst and hydrogen gas generated directly by a living microorganism. This biocompatible transformation, which requires both catalyst and microbe, and can be used on a preparative scale, represents a new strategy for chemical synthesis that combines organic chemistry and metabolic engineering.     

Multichannel Conductance of Folded Single‐Molecule Wires Aided by Through‐Space Conjugation

Deciphering charge transport through multichannel pathways in single‐molecule junctions is of high importance to construct nanoscale electronic devices and deepen insight into biological redox processes. Herein, we report two tailor‐made folded single‐molecule wires featuring intramolecular π–π stacking interactions. The scanning tunneling microscope (STM) based break‐junction technique and theoretical calculations show that through‐bond and through‐space conjugations are integrated into one single‐molecule wire, allowing for two simultaneous conducting channels in a single‐molecule junction. These folded molecules with stable π–π stacking interaction offer conceptual advances in single‐molecule multichannel conductance, and are perfect models for conductance studies in biological systems, organic thin films, and π‐stacked columnar aggregates.     

A Novel Oscillating Chemical Reaction Using Ninhydrin as Single Organic Substrate

Nonlinear chemistry has been a focus in recent years1. Many chemical oscillating reactions have been found and studied intensively, such as Belousov-Zhabotinskii (BZ) reaction2, Briggs-Rauscher reaction3, peroxidase-oxidase4, Bray-Liebhafsky reaction5 and…     

环戊二噻吩中的硫原子被CH2、SiH2取代对化合物光电性质影响的理论研究

有机电致发光材料是国际上的研究热点之一。本文采用量子化学方法,研究了环戊二噻吩CH2和SiH2取代对其与2,1,3-苯并噻二唑和三苯胺的化合物光电性质的影响。研究结果表明,CH2取代对母体分子的电子和光谱性质的影响比SiH2取代明显。SiH2取代使吸收和发射光谱的振子强度增大的程度大于CH2取代,更有利于发光强度的提高。CH2和SiH2取代衍生物的空穴和电子重组能的差值极小,可以作为有机电致发光二极管中双极性电荷传输材料。静电势能结果表明,SiH2取代衍生物的稳定性高于母体分子的稳定性。通过探索分子结构与性质间关系,为实验设计合成新的有机电致发光材料提供了理论支持。     

Structure and property studies of hybrid xerogels containing bridged positively charged 1,4-diazoniabicycle[2.2.2]octane dichloride

The compound di-3-n-propyltrimethoxysilane (1,4-diazoniabicycle[2.2.2]octane) dichloride, [(MeO)3Si(CH2)3N+ (CH2CH2)3N+ (CH2)3Si(OME)3]Cl2 was obtained and was used as a precursor reagent to obtain hybrid xerogels where the organic molecule was bonded to a silica framework by reacting the ends of both sides of the precursor reagent. That is, both -Si(OME)3 groups react with tetraethylorthosilicate (TEOS) by hydrolysis-condensation reactions. The resulting hybrid xerogels with variable C/Si mole ratios were prepared and analyzed and their textural characteristics determined. The samples prepared presented micropores with diameter 1.5 nm, the chain length of which matched with the estimated length of the organic bridging group. The charged organic bridging groups allow the immobilization of hexacyanoferrate ions by an ion exchange process. The electron transfer process of the hexacyanoferrate anionic complex confined in the pores of the matrices was studied by cyclovoltammetry.     

基于钯催化C-H键活化的多米诺反应

近年来,多米诺反应作为一种合成复杂分子的高效手段已得到有机合成化学家的广泛关注。该反应过程中,不需改变反应条件和添加试剂,中间体也无需分离和提纯,实现了原子经济和环境友好。通过C-H键活化直接构建碳-碳键和碳-杂原子键,大大拓展了传统偶联反应的底物范围,同样具有高原子经济性,已经广泛地作为多米诺反应中的一个高效步骤。此外,钯催化剂运用广泛,能够与多种官能团兼容,是多米诺反应的理想金属催化剂。本文综述了基于钯催化C-H键活化的多米诺反应的最新研究进展,以反应中钯的价态变化进行分类,介绍有关反应的特点、优势及其在天然产物合成中的应用。     

Organic synthesis in the solid state via hydrogen-bond-driven self-assembly

This Perspective describes how chemists can control intermolecular [2 + 2] photodimerizations in the solid state using small molecules as linear templates. The templates assemble olefins into positions for the reaction via hydrogen-bond-driven self-assembly. We attach functional groups to the olefins that complement hydrogen bond donor and acceptor groups of the templates. The resulting cyclobutane-based products form stereospecifically, quantitatively, and in gram amounts. The templates are used to direct the formation of a [2.2]paracyclophane and ladderanes. The organic solid state is an exciting medium within which to control chemical reactivity since it is possible to synthesize, or construct, molecules that may be, otherwise, unobtainable from solution. The products form with a high degree of stereocontrol provided by a crystal lattice. The critical covalent-bond-forming process also occurs in a solvent-free environment. That molecules are virtually frozen in position in a solid also means that this methodology enables chemists to employ principles of molecular recognition and self-assembly to direct and conduct organic synthesis.     

三原子分子振转激发态的理论研究

三原子分子振转激发态的理论研究谢代前,鄢国森,田安民（四川大学化学系,成都,６１００６４）关键词振转激发态,三原子分子,变分法能级较高的振转激发态通常包含大振幅运动,其波函数分布于很广的势能面区域内,传统的正则模理论已不适合于解决这类问题．近年来,Ｈ...     

Hydration properties of symmetric chain and asymmetric chain sphingomyelin bilayers

Hydration properties of lipid bilayer systems are compared for symmetric chain sphingomyelin (N-palmitoylsphingomyelin) and asymmetric chain sphingomyelin (N-lignoceroylsphingomyelin). These sphingomyelins were semisynthesized by a deacylation- reacylation process with a natural sphingomyelin used as a starting material. The number of differently bound water molecules was estimated by a deconvolution analysis of the ice-melting curves obtained by a differential scanning calorimetry (DSC) and was used to construct a water distribution diagram for these water molecules. Similarly to a natural sphingomyelin used for comparison, the asymmetric chain sphingomyelin was found to form small size vesicles having an internal cavity and incorporate 15 water molecules per molecule of lipid into its cavity, in contrast with 5 H₂O/lipid for freezable interlamellar water observed for large size multilamellar vesicles formed by the symmetric chain sphingomyelin.     

Lipocalin文库的构建及与克百威有结合活性的小分子筛选

构建大菜粉蝶Lipocalin蛋白家族中的BBP蛋白突变文库, 依据基因序列, 分别设计10条和12条引物, 通过PCR重叠延伸法得到包含随机突变蛋白BBP的基因序列, 并重组到噬菌粒载体pCANTAB5E中构建Lipocalin突变文库, 库容达到4.0×109. 以偶联分子BSA-克百威和OVA-克百威为靶分子, 采用柱式和平皿式交叉法对Lipocalin文库进行了筛选, 用竞争洗脱法洗脱特异结合活性的噬菌体. 经过3轮筛选, 从第3轮的洗脱液中随机挑选了10个重组克隆, 用Dot-blotting法检测出K7 anticalin分子能与克百威特异结合. 为研发克百威的Anticalin类检测试剂盒提供了候选分子, 也为拓宽Lipocalin文库在有害小分子检测方面的应用奠定了基础.     

Visible‐light‐driven self‐cleaning SERS substrate of silver nanoparticles and graphene oxide decorated nitrogen‐doped titania nanotube array

Graphene oxide (GO) and silver nanoparticles (Ag NPs) sequentially decorated nitrogen‐doped titania nanotube array (N‐TiO₂ NTA) had been designed as visible‐light‐driven self‐cleaning surface‐enhanced Raman scattering (SERS) substrate for a recyclable SERS detection application. N‐TiO₂ NTA was fabricated by anodic oxidation and then doping nitrogen treatment in ammonia atmosphere, acting as a visible‐light‐driven photocatalyst and supporting substrate. Ag/GO/N‐TiO₂ NTA was prepared by decorating GO monolayer through an impregnation process and then depositing Ag NPs through a polyol process on the surface of N‐TiO₂ NTA, acting as the collection of organic molecule and Raman enhancement. The SERS activity of Ag/GO/N‐TiO₂ NTA was evaluated using methyl blue as an organic probe molecule, revealing the analytical enhancement factor of 4.54 × 10⁴. Ag/GO/N‐TiO₂ NTA was applied as active SERS substrate to determine a low‐affinity organic pollutant of bisphenol A, revealing the detection limit of as low as 5 × 10^?7 m . Ag/GO/N‐TiO₂ NTA could also achieve self‐cleaning function for a recycling utilization through visible‐light‐driven photocatalytic degradation of the adsorbed organic molecules. Ag/GO/N‐TiO₂ NTA has been successfully reused for five times without an obvious decay in accuracy and sensitivity for organic molecule detection. The unique properties of this SERS substrate enable it to have a promising application for the sensitive and recyclable SERS detection of low‐affinity organic molecules. Copyright © 2016 John Wiley & Sons, Ltd.     

Tafel Slopes in Relation to the Replacement of Adsorbed Water by Organic Molecules

Abstract

In the lecture presented by Prof. Reddy the role of water in determining the potential dependence of electrosorption of neutral organic molecules has been discussed. The process one considers is that of the replacement of a number of water molecules n by each organic molecule adsorbed. The dipole moments of the adsorbed water molecules interact with the electrical field in the double layer and hence cause a potential (or charge) dependent adsorption of the neutral organic molecule, even if the latter possesses no permanent dipole moment. The theory of this phenomenon has been worked out by Bockris, Devanathan and Muller. Corrections for lateral interactions between the adsorbed water molecules and for the permanent dipole moment of the electrosorbed neutral organic molecule have been made.^1,2     

An Efficient Method for the Conjugation of Hydrophilic and Hydrophobic Components by Solid‐Phase‐Assisted Disulfide Ligation

Chemical conjugation between hydrophilic and hydrophobic components is difficult because of their extremely different solubility. Herein, we report a new versatile method with a solid‐phase‐assisted disulfide ligation to overcome the difficulty of conjugation attributed to solubility. The method involves two steps in a one‐pot process: 1) loading of a hydrophobic molecule onto a resin in an organic solvent, and 2) release of the solid‐supported hydrophobic molecule as a conjugate with a hydrophilic molecule into an aqueous solvent. This strategy allows the use of a suitable solvent system for the substrates in each step. Conjugates of a water‐insoluble drug, plinabulin, with hydrophilic carriers that could not be prepared by solution‐phase reactions were obtained in moderate yields (29–45 %). This strategy is widely applicable to the conjugation of compounds with solubility problems.     

Reaction mechanism of oxidation, hydroxylation, and epoxidation by hypofluorous acid: a theoretical study of unusual H-bond-assisted catalysis

The oxidation of organic molecules by hypofluorous acid (HOF) was studied extensively and systematically by Rozen et al. Therefore, it seems appropriate to refer to the process as Rozen oxidation. An entire set of model molecules was selected for quantum chemical investigation of the oxidation mechanism: a C=C double bond in ethylene, sulfur and selenium in dimethyl derivatives, nitrogen and phosphorus in trimethyl derivatives, as well as methyl azides. In the gas phase, van der Waals complexes between HOF and the previously mentioned species easily are formed, but these complexes are reluctant to undergo oxidation. The addition of another HOF molecule connected with the formation of a cyclic complex (i.e., substrate and two molecules of HOF) seems to be decisive for the oxidation process. The attempt to substitute the second HOF molecule with H2O demonstrated the superiority of HOF. Complexes of this kind decompose along the reaction path smoothly (i.e., with a low activation energy) to the respective oxidation product. A potential role of the hydroxyl cation (HO+) in the oxidation step is mentioned. Besides an oxidation product, one HOF molecule is released (an essential feature of catalysis), and furthermore, hydrogen fluoride is formed. It was suggested by Sertchook et al. (J. Phys. Chem. A 2006, 110, 8275) that the interaction between the substrate to be oxidized and HOF is catalytically influenced by the HF molecule. The mechanism suggested here is more feasible and, particularly at the early stages of the oxidation process, decisive. Also, the role of acetonitrile, used as a solvent by Rozen et al., is discussed in terms of a continuum model. Moreover, passing from potential energies to Gibbs energies is considered.     

Self-assembled monolayers and preorganization of organosilanes prior to surface grafting onto silica: a quantum mechanical study

Quantum chemical calculations have been carried out on the grafting of chain organosilane compounds on SiO(2)-hydroxylated solid surfaces. It is shown that a single molecule interacting with the surface lies flat to it, inhibiting further homogeneous film growth. This adsorption exhibits two molecule/surface interactions: a covalent bond on one side of the molecule and a hydrogen bond on the other side. We then investigate the possible preorganization of the molecules before grafting due to the presence of water molecules either in the gas/liquid phase or near the surface. This gives rise to the formation of dimerized chains. We then demonstrate that this preorganization process prevents subsequent lying flat of the molecules to the substrate after grafting. Energetics and associated configurations of the overall deposition process are discussed in detail and provide new insights on the understanding of the formation of self-assembled homogeneous organic films on microelectronics-type substrates.     

Radiation-induced transformations of isolated organic molecules in solid rare gas matrices

The radiation-chemical behaviour of isolated organic molecules in solid rare gas matrices was studied using a combination of ESR and IR spectroscopy. The total radiation-chemical yields of degradation of organic molecules in solid argon and xenon were estimated. The effect of electron scavengers on the radiolysis of organic molecules in solid rare gases reveals that the main primary process is positive hole transfer from matrix to guest molecule. ESR spectra of a number of radical cations (alkanes, ethers, arenes) were characterized in a low-disturbing environment. It was found that the electronic characteristics (IP, polarizability) of the matrix used had crucial effect on trapping and reactions of the isolated radical cations.     

新型双功能复合电极的制备及其加速水中有机污染物降解作用的研究

介绍了新型复合电极的制备方法、其双功能特性以及在提高水中有机污染物(如苯胺)降解速度所起的作用,并对其作用机制进行了讨论.实验结果表明,由空气电极和TiO₂光催化剂组成的复合电极,当其工作电位控制在0.05V(vs.SCE)左右时,既具有良好的光电效应,又具有以较高效率合成H₂O₂的特性,使溶液中的有机分子获得来自光催化氧化与光化学氧化两方面的联合降解作用,从而显著地提高了有机分子的氧化降解速度.     

Carbon,Nitrogen, and Chalcogen Substitution Effects on 2,1,3-Benzothiadiazole Derivative: Theoretical Investigations of Electronic,Optical, and Charge Transport Properties

A series of CH₂, NH, O, and Se substituted 2,1,3-benzothiadiazole derivatives have been de-signed and investigated computationally to elucidate their potential as organic light-emitting materials for organic light-emitting diodes. Both ab initio Hartree-Fock and hybrid density functional methods are used. It is found that adjusting the central aromatic ring by replacing S by CH₂, NH, O, and Se makes it possible to fine-tune the electronic, optical, and charge transport properties of the pristine molecule.