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Accounts of Chemical Research

Cyril Poriel, Joëlle Rault-Berthelot
Bridged oligophenylenes are very important organic semiconductors (OSCs) in organic electronics (OE). The fluorene unit, which is a bridged biphenyl, is the spearhead of this class of materials and has, over the last 20 years, led to fantastic breakthroughs in organic light-emitting diodes. Dihydroindenofluorenes belong to the family of bridged terphenyls and can be viewed as the fusion of a fluorene unit with an indene fragment. Dihydroindenofluorenes have also appeared as very promising building blocks for OE applications...
July 18, 2018: Accounts of Chemical Research
Harry B Gray, Jay R Winkler
Work on the electronic structures of metal-oxo complexes began in Copenhagen over 50 years ago. This work led to the prediction that tetragonal multiply bonded transition metal-oxos would not be stable beyond the iron-ruthenium-osmium oxo wall in the periodic table and that triply bonded metal-oxos could not be protonated, even in the strongest Brønsted acids. In this theory, only double bonded metal-oxos could attract protons, with basicities being a function of the electron donating ability of ancillary ligands...
July 17, 2018: Accounts of Chemical Research
Leesa M Smith, Heather M Aitken, Michelle L Coote
Bolland and Gee's basic autoxidation scheme (BAS) for lipids and rubbers has long been accepted as a general scheme for the autoxidation of all polymers. This scheme describes a chain process of initiation, propagation, and termination to describe the degradation of polymers in the presence of O2 . Central to this scheme is the conjecture that propagation of damage to the next polymer chain occurs via hydrogen atom transfer with a peroxyl radical. However, this reaction is strongly thermodynamically disfavored for all but unsaturated polymers, where the product allylic radical is resonance-stabilized...
July 17, 2018: Accounts of Chemical Research
Haopeng Xiao, Suttipong Suttapitugsakul, Fangxu Sun, Ronghu Wu
Glycosylation is one of the most common protein modifications, and it is essential for mammalian cell survival. It often determines protein folding and trafficking, and regulates nearly every extracellular activity, including cell-cell communication and cell-matrix interactions. Aberrant protein glycosylation events are hallmarks of human diseases such as cancer and infectious diseases. Therefore, glycoproteins can serve as effective biomarkers for disease detection and targets for drug and vaccine development...
July 16, 2018: Accounts of Chemical Research
Kecheng Jie, Yujuan Zhou, Errui Li, Feihe Huang
Porous materials with high surface areas have drawn more and more attention in recent years because of their wide applications in physical adsorption and energy-efficient adsorptive separation processes. Most of the reported porous materials are macromolecular porous materials, such as zeolites, metal-organic frameworks (MOFs), or porous coordination polymers (PCPs), and porous organic polymers (POPs) or covalent organic frameworks (COFs), in which the building blocks are linked together by covalent or coordinative bonds...
July 16, 2018: Accounts of Chemical Research
Faiyaz Khan, Michael Dlugosch, Xin Liu, Martin G Banwell
Cross-coupling reactions, especially those that are catalyzed by palladium, have revolutionized the way in which carbon-carbon bonds can be formed. The most commonly deployed variants of such processes are the Suzuki-Miyaura, Mizoroki-Heck, Stille, and Negishi cross-coupling reactions, and these normally involve the linking of an organohalide or pseudohalide (such as a triflate or nonaflate) with an organo-metallic or -metalloid such as an organo-boron, -magnesium, -tin, or -zinc species. Since the latter type of coupling partner is often prepared from the corresponding halide, methods that allow for the direct cross-coupling of two distinct halogen-containing compounds would provide valuable and more atom-economical capacities for the formation of carbon-carbon bonds...
July 16, 2018: Accounts of Chemical Research
Michael Haumann, Sven T Stripp
Over the past two decades, the bioinorganic chemistry of hydrogenases has attracted much interest from basic and applied research. Hydrogenases are highly efficient metalloenzymes that catalyze the reversible reduction of protons to molecular hydrogen (H2 ) in all domains of life. Their iron- and nickel-based cofactors represent promising blueprints for the design of biomimetic, synthetic catalysts. In this Account, we address the molecular proceedings of hydrogen turnover with [FeFe]-hydrogenases. The active site cofactor of [FeFe]-hydrogenases ("H-cluster") comprises a unique diiron complex linked to a [4Fe-4S] cluster via a single cysteine...
July 12, 2018: Accounts of Chemical Research
Ye Lu, Hai-Ning Zhang, Guo-Xin Jin
Over the last two decades, interlocked molecular species have received considerable attention, not only because of their intriguing structures and topological importance, but also because of their potential applications as smart materials, nanoscale devices, and molecular machines. Through judicious choice of metal centers and their adjoining ligands, a range of interesting interlocked structures have been realized by coordination-driven self-assembly. In addition, researchers have extensively developed synthetic methodologies for the construction of organized self-assemblies...
July 10, 2018: Accounts of Chemical Research
Cuiling Li, Muhammad Iqbal, Jianjian Lin, Xiliang Luo, Bo Jiang, Victor Malgras, Kevin C-W Wu, Jeonghun Kim, Yusuke Yamauchi
Well-constructed porous materials take an essential role in a wide range of applications, including energy conversion and storage systems, electrocatalysis, photocatalysis, and sensing. Although the tailored design of various nanoarchitectures has made substantial progress, simpler preparation methods are compelled to meet large-scale production requirements. Recently, advanced electrochemical deposition techniques have had a significant impact in terms of precise control upon the nanoporous architecture (i...
July 9, 2018: Accounts of Chemical Research
Han Liu, Xuechen Li
Synthetic proteins are expected to go beyond the boundary of recombinant DNA expression systems by being flexibly installed with site-specific natural or unnatural modification structures during synthesis. To enable protein chemical synthesis, peptide ligations provide effective strategies to assemble short peptide fragments obtained from solid-phase peptide synthesis (SPPS) into long peptides and proteins. In this regard, chemoselective peptide ligation represents a simple but powerful transformation realizing selective amide formation between the C-terminus and N-terminus of two side-chain-unprotected peptide fragments...
July 6, 2018: Accounts of Chemical Research
Sai Ho Pun, Qian Miao
Negatively curved carbons are theoretical carbon allotropes as proposed by embedding heptagons or octagons in a graphitic lattice. Unlike five-membered rings in fullerenes, which induce positive curvature, the seven- or eight-membered rings induce negative curvature, giving rise to a variety of esthetic carbon nanostructures known as Mackay crystals or carbon schwarzites. In addition, hypothetical toroidal carbon nanotubes consisting of five-, six-, and seven-membered rings present positive curvature on the outside and negative curvature on the inside of the torus...
July 5, 2018: Accounts of Chemical Research
Song Yang, Min Shi
Vinylidenecyclopropanes (VDCPs), having an allene moiety connected to a highly strained cyclopropyl group, have attracted a substantial amount of attention since they are fascinating building blocks for organic synthesis. During recent years, the reactions of VDCPs in the presence of a Lewis acid or a Brønsted acid and those induced by heat or light have experienced significant advancements due to the unique structural and electronic properties of VDCPs. Transition-metal-catalyzed reactions of VDCPs were not intensely investigated until the last 5 years...
June 29, 2018: Accounts of Chemical Research
Yifu Yu, Yanmei Shi, Bin Zhang
The rational synthesis of advanced nanomaterials with well-defined structures has been intensively studied due to the remarkable properties and intriguing applications of the formed materials. Recently, inorganic-organic hybrids have been widely adopted as precursors for chemical transformations toward the preparation of diverse nanomaterials. Specifically, inorganic and organic species with nano/molecule/atom-scale distribution serve as self-templates and sacrificial agents, respectively, endowing the products with controlled morphologies, band gaps, defects, and spatial architectures...
June 22, 2018: Accounts of Chemical Research
Samir Z Zard
The alkylation of enolates is one of the backbones of ketone chemistry, yet in practice it suffers from numerous limitations due to problems of regiochemistry (including O- versus C-alkylation), multiple alkylations, self-condensation, competing elimination, and incompatibility with many polar groups that have to be protected. Over the years, various solutions have been devised to overcome these difficulties, such as the employment of auxiliary ester or sulfone groups to modify the p Ka of the enolizable hydrogens, the passage by the corresponding hydrazones, the use of transition-metal-catalyzed redox systems to formally alkylate ketones with alcohols, etc...
June 22, 2018: Accounts of Chemical Research
Ieva Goldberga, Rui Li, Melinda J Duer
The extracellular matrix of a tissue is as important to life as the cells within it. Its detailed molecular structure defines the environment of a tissue's cells and thus their properties, including differentiation and metabolic status. Collagen proteins are the major component of extracellular matrices. Self-assembled collagen fibrils provide both specific mechanical properties to handle external stresses on tissues and, at the molecular level, well-defined protein binding sites to interact with cells. How the cell-matrix interactions are maintained against the stresses on the tissue is an important and as yet unanswered question...
June 22, 2018: Accounts of Chemical Research
Congqing Zhu, Haiping Xia
The construction of metal-carbon bonds is one of the most important issues of organometallic chemistry. However, the chelation of polydentate ligands to a metal via several metal-carbon bonds is rare. Metallapentalyne, which can be viewed as a 7-carbon (7C) chain coordinated to a metal via three metal-carbon bonds, was first reported in 2013. Although metallapentalyne contains a metal-carbon triple bond in a five-membered ring (5MR) and the bond angle around the carbyne carbon is only 129.5°, metallapentalyne exhibits excellent stability to air, moisture, and heat...
June 21, 2018: Accounts of Chemical Research
Ruquan Ye, Dustin K James, James M Tour
Research on graphene abounds, from fundamental science to device applications. In pursuit of complementary morphologies, formation of graphene foams is often preferred over the native two-dimensional (2D) forms due to the higher available area. Graphene foams have been successfully prepared by several routes including chemical vapor deposition (CVD) methods and by wet-chemical approaches. For these methods, one often needs either high temperature furnaces and highly pure gases or large amounts of strong acids and oxidants...
June 20, 2018: Accounts of Chemical Research
Peng Yang, Ulrich Kortz
Noble metal catalysts, in particular palladium-containing materials, are of prime commercial interest, because of their role as oxidation catalysts in automobile emission-control systems and reforming catalysts for the production of high-octane gasoline. However, despite almost two centuries of research, the precise structure of such materials is still ill-defined on the sub-nanometer scale, which severely limits the understanding of the underlying catalytic mechanisms. As a burgeoning class of structurally well-defined noble metal oxide nanoclusters, polyoxopalladates (POPs) have been highly rated as ideal models to fully decipher the molecular mechanism of noble metal-based catalysis...
June 18, 2018: Accounts of Chemical Research
Chenxi Wei, Sihao Xia, Hai Huang, Yuwei Mao, Piero Pianetta, Yijin Liu
Functional materials and devices are usually morphologically complex and chemically heterogeneous. Their structures are often designed to be hierarchical because of the desired functionalities, which usually require many different components to work together in a coherent manner. The lithium ion battery, as an energy storage device, is a very typical example of this kind of structure. In a lithium ion battery, the cathode, anode, and separator are soaked in a liquid electrolyte, facilitating the back and forward shuttling of the lithium ions for energy storage and release...
June 11, 2018: Accounts of Chemical Research
Kenneth S Suslick, Nathan C Eddingsaas, David J Flannigan, Stephen D Hopkins, Hangxun Xu
Acoustic cavitation (the growth, oscillation, and rapid collapse of bubbles in a liquid) occurs in all liquids irradiated with sufficient intensity of sound or ultrasound. The collapse of such bubbles creates local heating and provides a unique source of energy for driving chemical reactions. In addition to sonochemical bond scission and formation, cavitation also induces light emission in many liquids. This phenomenon of sonoluminescence (SL) has captured the imagination of many researchers since it was first observed 85 years ago...
May 17, 2018: Accounts of Chemical Research
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