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Accounts of Chemical Research

Zitong Liu, Guanxin Zhang, Deqing Zhang
Organic semiconductors have received increasing attentions in recent years because of their promising applications in various optoelectronic devices. The key performance metric for organic semiconductors is charge carrier mobility, which is governed by the electronic structures of conjugated backbones and intermolecular/interchain π-π interactions and packing in both microscopic and macroscopic levels. For this reason, more efforts have been paid to the design and synthesis of conjugated frameworks for organic semiconductors with high charge mobilities...
May 17, 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
Suresh K Vasa, Petra Rovó, Rasmus Linser
Solid-state nuclear magnetic resonance (ssNMR) is a spectroscopic technique that is used for characterization of molecular properties in the solid phase at atomic resolution. In particular, using the approach of magic-angle spinning (MAS), ssNMR has seen widespread applications for topics ranging from material sciences to catalysis, metabolomics, and structural biology, where both isotropic and anisotropic parameters can be exploited for a detailed assessment of molecular properties. High-resolution detection of protons long represented the holy grail of the field...
May 15, 2018: Accounts of Chemical Research
Xingyue Ji, Binghe Wang
Carbon monoxide is widely acknowledged as an important gasotransmitter in the mammalian system with importance on par with that of nitric oxide. It has also been firmly established as a potential therapeutic agent with a wide range of indications including organ transplantation, cancer, bacterial infection, and inflammation-related conditions such as colitis and sepsis. One major issue in developing CO based therapeutics is its delivery in a pharmaceutically acceptable form. Currently, there are generally five forms of deliveries: inhaled CO, photosensitive CO-releasing molecules, encapsulated CO, CO dissolved in drinks, and molecules that would release CO under physiological conditions without the need for light...
May 15, 2018: Accounts of Chemical Research
Michael Z Kamrath, Thomas R Rizzo
Ion mobility spectrometry (IMS) has become a valuable tool in biophysical and bioanalytical chemistry because of its ability to separate and characterize the structure of gas-phase biomolecular ions on the basis of their collisional cross section (CCS). Its importance has grown with the realization that in many cases, biomolecular ions retain important structural characteristics when produced in the gas phase by electrospray ionization (ESI). While a CCS can help distinguish between structures of radically different types, one cannot expect a single number to differentiate similar conformations of a complex molecule...
May 10, 2018: Accounts of Chemical Research
Alex Inthasot, Shun-Te Tung, Sheng-Hsien Chiu
In 1987, Pedersen, Cram, and Lehn were awarded the Nobel Prize in Chemistry to honor their achievements in, among other things, the selective recognition of alkali metal ions by synthetic hosts. Almost three decades later, the 2016 Nobel Prize went to Stoddart, Sauvage, and Feringa for the development of artificial molecular machines, in which interlocked molecules play a significant role. Surprisingly, although many rotaxane- and catenane-based molecular machines have been constructed using various templating approaches, alkali metal ions, which are good templates for crown ether synthesis, have only rarely been applied as templates for the assembly of these interlocked molecules...
May 10, 2018: Accounts of Chemical Research
Tian Zhao, Patrick J Herbert, Hongjun Zheng, Kenneth L Knappenberger
Electronic carrier dynamics play pivotal roles in the functional properties of nanomaterials. For colloidal metals, the mechanisms and influences of these dynamics are structure dependent. The coherent carrier dynamics of collective plasmon modes for nanoparticles (approximately 2 nm and larger) determine optical amplification factors that are important to applied spectroscopy techniques. In the nanocluster domain (sub-2 nm), carrier coupling to vibrational modes affects photoluminescence yields. The performance of photocatalytic materials featuring both nanoparticles and nanoclusters also depends on the relaxation dynamics of nonequilibrium charge carriers...
May 8, 2018: Accounts of Chemical Research
Qinming Wu, Xiangju Meng, Xionghou Gao, Feng-Shou Xiao
Zeolites have been extensively studied for years in different areas of chemical industry, such as shape selective catalysis, ion-exchange, and gas adsorption and separation. Generally, zeolites are prepared from solvothermal synthesis in the presence of a large amounts of solvents such as water and alcohols in sealed autoclaves under autogenous pressure. Water has been regarded as essential to synthesize zeolites for fast mass transfer of reactants, but it occupies a large space in autoclaves, which greatly reduces the yield of zeolite products...
May 8, 2018: Accounts of Chemical Research
Guangxue Feng, Bin Liu
Theranostic nanolights refer to luminescent nanoparticles possessing both imaging and therapeutic functions. Their shape, size, surface functions, and optical properties can be precisely manipulated through integrated efforts of chemistry, materials, and nanotechnology for customized applications. When localized photons are used to activate both imaging and therapeutic functions such as photodynamic or photothermal therapy, these theranostic nanolights increase treatment efficacy with minimized damage to surrounding healthy tissues, which represents a promising noninvasive nanomedicine as compared to conventional theranostic approaches...
May 7, 2018: Accounts of Chemical Research
Binh T Mai, Soraia Fernandes, Preethi B Balakrishnan, Teresa Pellegrino
Combining hard matter, like inorganic nanocrystals, and soft materials, like polymers, can generate multipurpose materials with a broader range of applications with respect to the individual building blocks. Given their unique properties at the nanoscale, magnetic nanoparticles (MNPs) have drawn a great deal of interest due to their potential use in the biomedical field, targeting several applications such as heat hubs in magnetic hyperthermia (MHT, a heat-damage based therapy), contrast agents in magnetic resonance imaging (MRI), and nanocarriers for targeted drug delivery...
May 7, 2018: Accounts of Chemical Research
Hiroyuki Katsuki, Nobuyuki Takei, Christian Sommer, Kenji Ohmori
Coherent control is a technique to manipulate wave functions of matter with light. Coherent control of isolated atoms and molecules in the gas phase is well-understood and developed since the 1990s, whereas its application to condensed matter is more difficult because its coherence lifetime is shorter. We have recently applied this technique to condensed matter samples, one of which is solid para-hydrogen ( p-H2 ). Intramolecular vibrational excitation of solid p-H2 gives an excited vibrational wave function called a "vibron", which is delocalized over many hydrogen molecules in a manner similar to a Frenkel exciton...
May 7, 2018: Accounts of Chemical Research
R David Row, Jennifer A Prescher
Chemical tools are transforming our understanding of biomolecules and living systems. Included in this group are bioorthogonal reagents-functional groups that are inert to most biological species, but can be selectively ligated with complementary probes, even in live cells and whole organisms. Applications of these tools have revealed fundamental new insights into biomolecule structure and function-information often beyond the reach of genetic approaches. In many cases, the knowledge gained from bioorthogonal probes has enabled new questions to be asked and innovative research to be pursued...
May 4, 2018: Accounts of Chemical Research
Seijiro Hosokawa
The construction of libraries of acyclic polyketides remains a challenging topic, mostly due to the difficulties associated with finding the right balance between diversity and brevity for the synthetic routes leading to polyketides. Recently, relatively short methods have been developed and applied to the synthesis of natural products. However, these short routes often suffer from limited diversity with respect to the arrangement of functional groups and stereochemistry, as these usually require reactions that direct multiple functional groups simultaneously in one step...
May 4, 2018: Accounts of Chemical Research
Hironori Tsunoyama, Masahiro Shibuta, Masato Nakaya, Toyoaki Eguchi, Atsushi Nakajima
Nanoclusters, aggregates of several to hundreds of atoms, have been one of the central issues of nanomaterials sciences owing to their unique structures and properties, which could be found neither in nanoparticles with several nanometer diameters nor in organometallic complexes. Along with the chemical nature of each element, properties of nanoclusters change dramatically with size parameters, making nanoclusters strong potential candidates for future tailor-made materials; these nanoclusters are expected to have attractive properties such as redox activity, catalysis, and magnetism...
May 1, 2018: Accounts of Chemical Research
Connor W Coley, William H Green, Klavs F Jensen
Computer-aided synthesis planning (CASP) is focused on the goal of accelerating the process by which chemists decide how to synthesize small molecule compounds. The ideal CASP program would take a molecular structure as input and output a sorted list of detailed reaction schemes that each connect that target to purchasable starting materials via a series of chemically feasible reaction steps. Early work in this field relied on expert-crafted reaction rules and heuristics to describe possible retrosynthetic disconnections and selectivity rules but suffered from incompleteness, infeasible suggestions, and human bias...
May 1, 2018: Accounts of Chemical Research
Qian Wang, De-Xian Wang, Mei-Xiang Wang, Jieping Zhu
The Passerini three-component (P-3CR) and the Ugi four-component (U-4CR) are two of the most prominent isocyanide-based multicomponent reactions (IMCRs). The P-3CR transforms isocyanides, aldehydes (ketones), and carboxylic acids to α-acyloxy carboxamides, while the U-4CR converts isocyanides, aldehydes (ketones), amines, and carboxylic acids to α-acetamido carboxamides. Conversion of the high energy formal divalent isocyano carbon into a tetravalent amide carbonyl carbon provides the driving force for these reactions...
April 30, 2018: Accounts of Chemical Research
Christian Petermayer, Henry Dube
Indigoid photoswitches comprise a class of chromophores that are derived from the parent and well-known indigo dye. Different from most photoswitches their core structures absorb in the visible region of the spectrum in both isomeric states even without substitutions, which makes them especially interesting for applications not tolerant of high-energy UV light. Also different from most current photoswitching systems, they provide highly rigid structures that undergo large yet precisely controllable geometry changes upon photoisomerization...
April 25, 2018: Accounts of Chemical Research
Sihong Wang, Jin Young Oh, Jie Xu, Helen Tran, Zhenan Bao
Future electronics will take on more important roles in people's lives. They need to allow more intimate contact with human beings to enable advanced health monitoring, disease detection, medical therapies, and human-machine interfacing. However, current electronics are rigid, nondegradable and cannot self-repair, while the human body is soft, dynamic, stretchable, biodegradable, and self-healing. Therefore, it is critical to develop a new class of electronic materials that incorporate skinlike properties, including stretchability for conformable integration, minimal discomfort and suppressed invasive reactions; self-healing for long-term durability under harsh mechanical conditions; and biodegradability for reducing environmental impact and obviating the need for secondary device removal for medical implants...
April 25, 2018: Accounts of Chemical Research
Elena Meirzadeh, Isabelle Weissbuch, David Ehre, Meir Lahav, Igor Lubomirsky
Crystals are physical arrays delineated by polar surfaces and often contain imperfections of a polar nature. Understanding the structure of such defects on the molecular level is of topical importance since they strongly affect the macroscopic properties of materials. Moreover, polar imperfections in crystals can be created intentionally and specifically designed by doping nonpolar crystals with "tailor-made" additives as dopants, since their incorporation generally takes place in a polar mode. Insertion of dopants also induces a polar deformation of neighboring host molecules, resulting in the creation of polar domains within the crystals...
April 20, 2018: Accounts of Chemical Research
Igor V Alabugin, Edgar Gonzalez-Rodriguez
Do not bend the triple bonds! This familiar undergraduate mantra must be disobeyed if the alkyne group is used as a building block in molecular construction. This Account will describe our exploits in "alkyne origami", that is, folding oligoalkynes into new shapes via cyclization cascades. This research stems from a set of guidelines for the cyclizations of alkynes that we suggested in 2011 ( Gilmore Chem. Rev. 2011 , 111 , 6513 ; Alabugin J. Am. Chem. Soc. 2011 , 133 , 12608 ). The guidelines blended critical analysis of ∼40 years of experimental research with computations into the comprehensive predictions of the relative favorability of dig-cyclizations of anions and radicals...
April 20, 2018: Accounts of Chemical Research
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