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Accounts of Chemical Research

Julia W Darcy, Brian Koronkiewicz, Giovanny A Parada, James M Mayer
Proton-coupled electron transfer (PCET) covers a wide range of reactions involving the transfer(s) of electrons and protons. The best-known PCET reaction, hydrogen atom transfer (HAT), has been studied in detail for more than a century. HAT is generally described as the concerted transfer of a hydrogen atom (H• ≡ H+ + e- ) from one group to another, Y + H-X → Y-H + X, but a strict definition of HAT has been difficult to establish. Distinctions are more challenging when the transfer of "H• " involves e- and H+ that transfer to/from spatially distinct sites or even completely separate reagents (multiple-site concerted proton-electron transfer, MS-CPET)...
September 20, 2018: Accounts of Chemical Research
Yanyan Liu, Yaqin Jiang, Meng Zhang, Zhongmin Tang, Mingyuan He, Wenbo Bu
The common existence of hypoxia in solid tumors has been heavily researched because it renders tumors more resistant to most standard therapeutic methods, such as radiotherapy (RT), chemotherapy, and photodynamic therapy (PDT), and is associated with a more malignant phenotype and poor survival in patients with tumors. The development of hypoxia modulation methods for advanced therapeutic activity is therefore of great interest but remains a considerable challenge. Since the significant development of nanotechnology and nanomedicine, functionalized nanomaterials can be exploited as adjuvant "drugs" for these oxygen-dependent standard therapies or as hypoxia initiators for advanced new therapies to solid tumors...
September 20, 2018: Accounts of Chemical Research
Mengqi Zeng, Lei Fu
Due to the confinement of the charge, spin, and heat transport in the plane, graphene and related two-dimensional (2D) materials have been demonstrated to own many unique and excellent properties and witnessed many breakthroughs in physics. They show great application potential in many fields, especially for electronics and optoelectronics. However, a bottleneck to widespread applications is precise and reliable fabrication, in which the control of the layer number and domain assembly is the most basic and important since they directly determine the qualities and properties of 2D materials...
September 17, 2018: Accounts of Chemical Research
Thomas Just Sørensen, Stephen Faulkner
Kinetically inert lanthanide complexes are proving to be highly effective building blocks for the preparation of complex heterometallic architectures, allowing complete control of metal ion domains, which cannot be achieved under thermodynamic control. Kinetic stability may render perceivable labile coordination bonds more durable than several types of covalent interactions. For complexes in clinical use, the significance of kinetic stability cannot be overstated, and this Account treats the topic accordingly...
September 17, 2018: Accounts of Chemical Research
Dawei Zhang, Tanya K Ronson, Jonathan R Nitschke
Coordination-driven self-assembly can produce large, symmetrical, hollow cages that are synthetically easy to access. The functions provided by these aesthetically attractive structures provide a driving force for their development, enabling practical applications. For instance, cages have provided new methods of molecular recognition, chirality sensing, separations, stabilization of reactive species, and catalysis. We have fruitfully employed subcomponent self-assembly to prepare metal-organic capsules from simple building blocks via the simultaneous formation of dynamic coordinative (N→metal) and covalent (N═C) bonds...
September 12, 2018: Accounts of Chemical Research
Bryan Robertson, Mu-Jie Huang, Jiang-Xing Chen, Raymond Kapral
Active matter, some of whose constituent elements are active agents that can move autonomously, behaves very differently from matter without such agents. The active agents can self-assemble into structures with a variety of forms and dynamical properties. Swarming, where groups of living agents move cooperatively, is commonly observed in the biological realm, but it is also seen in the physical realm in systems containing small synthetic motors. The existence of diverse forms of self-assembled structures has stimulated the search for new applications that involve active matter...
September 12, 2018: Accounts of Chemical Research
M Haris Mahyuddin, Yoshihito Shiota, Aleksandar Staykov, Kazunari Yoshizawa
As fossil-based energy sources become more depleted and with renewable-energy technologies still in a very early stage of development, the utilization of highly abundant methane as a transitional solution for current energy demands is highly important despite difficulties in transport and storage. Technologies enabling the conversion of methane to liquid/condensable energy carriers that can be easily transported and integrated into the existing chemical infrastructures are therefore essential. Although there commercially exists a two-step gas-to-liquid process involving syngas production, a novel route of methane conversion that can circumvent the high-cost production of syngas should be developed...
September 12, 2018: Accounts of Chemical Research
Heidi R Culver, John R Clegg, Nicholas A Peppas
No abstract text is available yet for this article.
September 11, 2018: Accounts of Chemical Research
Michael Mastalerz
The interest in shape-persistent organic cages is nearly as old as the interest in supramolecular chemistry. In the beginning, organic cages have often been synthesized in a stepwise manner, which is not only laborious but very often also accompanied by low overall yields. In 1988, MacDowell published the one pot high-yielding synthesis of [2 + 3] imine cages based on TREN and aromatic dialdehydes, exploiting the reversible condensation of amines and aldehydes to  imines, which was later used by others to make even larger cages on the basis of resorcinarenes...
September 11, 2018: Accounts of Chemical Research
David Bartee, Caren L Freel Meyers
Antibiotics are the cornerstone of modern healthcare. The 20th century discovery of sulfonamides and β-lactam antibiotics altered human society immensely. Simple bacterial infections were no longer a leading cause of morbidity and mortality, and antibiotic prophylaxis greatly reduced the risk of infection from surgery. The current healthcare system requires effective antibiotics to function. However, antibiotic-resistant infections are becoming increasingly prevalent, threatening the emergence of a postantibiotic era...
September 11, 2018: Accounts of Chemical Research
Jung Su Park, Jonathan L Sessler
Molecular and supramolecular systems capable of switching between two or more states as the result of an applied chemical stimulus are attracting ever-increasing attention. They have seen wide application in the development of functional materials including, but not limited to, molecular and supramolecular switches, chemosensors, electronics, optoelectronics, and logic gates. A wide range of chemical stimuli have been used to control the switching within bi- and multiple state systems made up from either singular molecular entities or supramolecular ensembles...
September 11, 2018: Accounts of Chemical Research
Siqi Zhang, Liang Zhao
Macrocyclic ligands have been extensively applied to recognize single metal ions with high selectivity and good affinity based on the size-match principle. The resulting metal-macrocycle complexes play a significant role in mimicking the function of natural metal ion carriers and understanding and reproducing the catalytic activity of metalloenzymes. Because of the known macrocyclic effect, those single metal-macrocycle adducts often show an enhanced kinetic and thermodynamic stability in comparison with their open-chain analogues...
September 10, 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
Jingxian Yu, John R Horsley, Andrew D Abell
Molecular electronics is at the forefront of interdisciplinary research, offering a significant extension of the capabilities of conventional silicon-based technology as well as providing a possible stand-alone alternative. Bio-inspired molecular electronics is a particularly intriguing paradigm, as charge transfer in proteins/peptides, for example, plays a critical role in the energy storage and conversion processes for all living organisms. However, the structure and conformation of even the simplest protein is extremely complex, and therefore, synthetic model peptides comprising well-defined geometry and predetermined functionality are ideal platforms to mimic nature for the elucidation of fundamental biological processes while also enhancing the design and development of single-peptide electronic components...
September 18, 2018: Accounts of Chemical Research
Sourav Saha
As counterintuitive as it might seem, in aprotic media, electron transfer (ET) from strong Lewis basic anions, particularly F- , OH- , and CN- , to certain π-acids (πA) is not only spectroscopically evident from the formation of paramagnetic πA•- radical anions and πA2- dianions, but also thermodynamically justified because these anions' highest occupied molecular orbitals (HOMOs) lie above the π-acids' lowest unoccupied molecular orbitals (LUMOs) creating negative free energy changes (Δ G°ET < 0)...
September 18, 2018: Accounts of Chemical Research
Maria Jose Esplandiu, Kuan Zhang, Jordi Fraxedas, Borja Sepulveda, David Reguera
The development of effective autonomous micro- and nanomotors relies on controlling fluid motion at interfaces. One of the main challenges in the engineering of such artificial machines is the quest for efficient mechanisms to power them without using external driving forces. In the past decade, there has been an important increase of man-made micro- and nanomotors fueled by self-generated physicochemical gradients. Impressive proofs of concept of multitasking machines have been reported demonstrating their capabilities for a plethora of applications...
September 18, 2018: Accounts of Chemical Research
Yingjie Zhao, Yoann Cotelle, Le Liu, Javier López-Andarias, Anna-Bea Bornhof, Masaaki Akamatsu, Naomi Sakai, Stefan Matile
The objective of this Account is to summarize the first five years of anion-π catalysis. The general idea of anion-π catalysis is to stabilize anionic transition states on aromatic surfaces. This is complementary to the stabilization of cationic transition states on aromatic surfaces, a mode of action that occurs in nature and is increasingly used in chemistry. Anion-π catalysis, however, rarely occurs in nature and has been unexplored in chemistry. Probably because the attraction of anions to π surfaces as such is counterintuitive, anion-π interactions in general are much younger than cation-π interactions and remain under-recognized until today...
September 18, 2018: Accounts of Chemical Research
Richard E Palmer, Rongsheng Cai, Jerome Vernieres
It is hard to predict the future of science. For example, when C60 and its structure were identified from the mass spectra of gas phase carbon clusters, few could have predicted the era of carbon nanotechnology which the discovery introduced. The solubilization and functionalization of C60 , the identification and then synthesis of carbon nanotubes, and the generation and physics of graphene have made a scale of impact on the international R&D (and to some extent industrial) landscape which could not have been foreseen...
September 18, 2018: Accounts of Chemical Research
Fei Wang, Pinhong Chen, Guosheng Liu
The direct transformation of C-H bonds into diverse functional groups represents one of the most atom- and step-economical strategies for organic synthesis and has received substantial attention over the last few decades. Despite recent advances, asymmetric C-H bond functionalizations are less developed, especially asymmetric oxidations of sp3 C-H bonds. Inspired by enzyme (e.g., P450) catalysis, chemists have made great efforts to develop non-enzymatic systems for enantioselective oxidations of sp3 C-H bonds...
September 18, 2018: Accounts of Chemical Research
Wonwoo Nam, Yong-Min Lee, Shunichi Fukuzumi
Molecular oxygen (O2 ), the greenest oxidant, is kinetically stable in the oxidation of organic substrates due to its triplet ground state. In nature, O2 is reduced by two electrons with two protons to produce hydrogen peroxide (H2 O2 ) and by four electrons with four protons to produce water (H2 O) by oxidase and oxygenase metalloenzymes. In the process of the two-electron/two-proton and four-electron/four-proton reduction of O2 by metalloenzymes and their model compounds, metal-oxygen intermediates, such as metal-superoxido, -peroxido, -hydroperoxido, and -oxido species, are generated depending on the numbers of electrons and protons involved in the O2 activation reactions...
September 18, 2018: Accounts of Chemical Research
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