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Accounts of Chemical Research

Alexander P Gorka, Roger R Nani, Martin J Schnermann
Optical approaches that visualize and manipulate biological processes have transformed modern biomedical research. An enduring challenge is to translate these powerful methods into increasingly complex physiological settings. Longer wavelengths, typically in the near-infrared (NIR) range (∼650-900 nm), can enable advances in both fundamental and clinical settings; however, suitable probe molecules are needed. The pentamethine and heptamethine cyanines, led by prototypes Cy5 and Cy7, are among the most useful compounds for fluorescence-based applications, finding broad use in a range of contexts...
November 12, 2018: Accounts of Chemical Research
Michael Kuron, Patrick Kreissl, Christian Holm
Active matter concerns itself with the study of particles that convert energy into work, typically motion of the particle itself. This field saw a surge of interest over the past decade, after the first micrometer-sized, man-made chemical motors were created. These particles served as a simple model system for studying in a well-controlled manner complex motion and cooperative behavior as known from biology. In addition, they have stimulated new efforts in understanding out-of-equilibrium statistical physics and started a revolution in microtechnology and robotics...
November 12, 2018: Accounts of Chemical Research
Gregorio Guisado-Barrios, Michèle Soleilhavoup, Guy Bertrand
Classical carbenes are usually described as neutral compounds featuring a divalent carbon with only six electrons in their valence shell. It was only in 1988 that our group prepared the first isolable example, in which the carbene center was stabilized by a push-pull effect, using a phosphino and a silyl substituent. In the last 30 years, a myriad of acyclic and cyclic push-pull and push-push carbenes, bearing different heteroatom substituents, have been isolated. Among them, the so-called N-heterocyclic carbenes (NHCs), which include cyclic (alkyl)(amino)carbenes (CAACs), are arguably the most popular...
November 12, 2018: Accounts of Chemical Research
Judit Horváth, István Szalai, Patrick De Kepper
Since Alan Turing's 1952 pioneering work, reaction-diffusion (RD) processes are regarded as prototype mechanisms for pattern formation in living systems. Though suspected in many aspects of morphogenetic development, pure RD patterns have not yet been demonstrated in living organisms. The first observations of an autonomous development of stationary chemical patterns were made in the early 1990s. In this Account, we discuss the recent developments for producing stationary pH RD patterns in open spatial reactors...
November 9, 2018: Accounts of Chemical Research
Jinhui Zhu, Chongqing Yang, Chenbao Lu, Fan Zhang, Zhanhui Yuan, Xiaodong Zhuang
Inorganic porous materials have long dominated the field of porous materials due to their stable structure and wide applications. In the past decade, porous polymers have generated considerable interest among researchers because of their easily tunable porosity, carbon-rich backbones, and prominent physical properties. These attributes enable porous polymers to be used in various applications such as sensing, gas separation and storage, catalysis, and energy storage. However, poor dispersibility has long hindered the development of porous polymers...
November 9, 2018: Accounts of Chemical Research
Samantha A Green, Steven W M Crossley, Jeishla L M Matos, Suhelen Vásquez-Céspedes, Sophia L Shevick, Ryan A Shenvi
The implementation of any chemical reaction in a structurally complex setting ( King , S. M. J. Org. Chem. 2014 , 79 , 8937 ) confronts structurally defined barriers: steric environment, functional group reactivity, product instability, and through-bond electronics. However, there are also practical barriers. Late-stage reactions conducted on small quantities of material are run inevitably at lower than optimal concentrations. Access to late-stage material limits extensive optimization. Impurities from past reactions can interfere, especially with catalytic reactions...
November 8, 2018: Accounts of Chemical Research
Jireh Joy D Sacramento, David P Goldberg
There has been considerable interest in hydrogen atom transfer (HAT) reactions mediated by metal/oxygen species because of their central role in metalloenzyme function as well as synthetic catalysts. This Account focuses on our progress in synthesizing high-valent metal-oxo and metal-hydroxo porphyrinoid complexes and determining their reactivities in a range of HAT processes. For these studies we have utilized corrolazine and corrole ligands, which are a ring-contracted subclass of porphyrinoid compounds designed to stabilize high-valent metal complexes...
November 7, 2018: Accounts of Chemical Research
Moo Yeol Lee, Hae Rang Lee, Cheol Hee Park, Seul Gi Han, Joon Hak Oh
Bioelectronics for healthcare that monitor the health information on users in real time have stepped into the limelight as crucial electronic devices for the future due to the increased demand for "point-of-care" testing, which is defined as medical diagnostic testing at the time and place of patient care. In contrast to traditional diagnostic testing, which is generally conducted at medical institutions with diagnostic instruments and requires a long time for specimen analysis, point-of-care testing can be accomplished personally at the bedside, and health information on users can be monitored in real time...
November 7, 2018: Accounts of Chemical Research
Mihail N Popescu, William E Uspal, Alvaro Domínguez, Siegfried Dietrich
Chemically active colloids can achieve force- and torque-free motility ("self-propulsion") via the promotion, on their surface, of catalytic chemical reactions involving the surrounding solution. Such systems are valuable both from a theoretical perspective, serving as paradigms for nonequilibrium processes, as well as from an application viewpoint, according to which active colloids are envisioned to play the role of carriers ("engines") in novel lab-on-a-chip devices. The motion of such colloids is intrinsically connected with a "chemical field", i...
November 7, 2018: Accounts of Chemical Research
Jayoung Kim, Itthipon Jeerapan, Juliane R Sempionatto, Abbas Barfidokht, Rupesh K Mishra, Alan S Campbell, Lee J Hubble, Joseph Wang
In this Account, we detail recent progress in wearable bioelectronic devices and discuss the future challenges and prospects of on-body noninvasive bioelectronic systems. Bioelectronics is a fast-growing interdisciplinary research field that involves interfacing biomaterials with electronics, covering an array of biodevices, encompassing biofuel cells, biosensors, ingestibles, and implantables. In particular, enzyme-based bioelectronics, built on diverse biocatalytic reactions, offers distinct advantages and represents a centerpiece of wearable biodevices...
November 6, 2018: Accounts of Chemical Research
Belén Nieto-Ortega, Thomas Bürgi
Over recent years, the field of thiolate-protected gold nanoclusters has made remarkable progress. The successful determination of the structure of some of these clusters by X-ray crystallography was a milestone in this field. X-ray crystallography is arguably the most important technique in the field up to now, and it enabled the study of structure evolution as a function of cluster size. It also shed light on the structure of the Au-S interface. Recently, it has been realized that thiolate-protected gold clusters are very dynamic systems...
November 6, 2018: Accounts of Chemical Research
Yang Yu, Julius Rebek
The chemistry of confined molecules is a relatively new undertaking, and this Account describes the effects of certain host container compounds on the behavior of molecules held as guests within. The containers are known as cavitands, which have one open end that allows small molecules to go in and out. The containers are amphiphilic: they feature aromatic surfaces that create a hydrophobic space inside but their peripheries are polar and permit solubility in water. The tension between the inner space of the cavitand and the outer space of the medium is experienced by the guest molecules...
November 6, 2018: Accounts of Chemical Research
Qing Tang, Guoxiang Hu, Victor Fung, De-En Jiang
Atomically precise, ligand-protected metal nanoclusters are of great interest for their well-defined structures, intriguing physicochemical properties, and potential applications in catalysis, biology, and nanotechnology. Their structure precision provides many opportunities to correlate their geometries, stability, electronic properties, and catalytic activities by closely integrating theory and experiment. In this Account, we highlight recent theoretical advances from our efforts to understand the metal-ligand interfaces, the energy landscape, the electronic structure and optical absorption, and the catalytic applications of atomically precise metal nanoclusters...
November 6, 2018: Accounts of Chemical Research
Shuxin Wang, Qi Li, Xi Kang, Manzhou Zhu
The properties of metal materials can be greatly enriched by including various elements to generate alloys. The galvanic replacement represents a classical method for the preparation of both bulk- and nanoalloy materials. The difference of the electrochemical potential between the two metals acts as the driving force for the galvanic replacement reaction. However, this classical rule partially fails at the ultrasmall size scale, for that novel chemistry emerges by the decrease of the size of materials down to less than 3 nm due to the strong quantum effect...
November 2, 2018: Accounts of Chemical Research
Max R Friedfeld, Jennifer L Stein, Andrew Ritchhart, Brandi M Cossairt
Clusters are unique molecular species that can be viewed as a bridge between phases of matter and thus between disciplines of chemistry. The structural and compositional complexity observed in cluster chemistry serves as an inspiration to the material science community and motivates our search for new phases of matter. Moreover, the formation of kinetically persistent cluster molecules as intermediates in the nucleation of crystals makes these materials of great interest for determining and controlling mechanisms of crystal growth...
November 2, 2018: Accounts of Chemical Research
Igor S Aranson
Active matter is a wide class of nonequilibrium systems consisting of interacting self-propelled agents transducing the energy stored in the environment into mechanical motion. Numerous examples range from microscopic cytoskeletal filaments and swimming organisms (bacteria and unicellular algae), synthetic catalytic nanomotors, colloidal self-propelled Janus particles, to macroscopic bird flocks, fish schools, and even human crowds. Active matter demonstrates a remarkable tendency toward self-organization and development of collective states with the long-range spatial order...
October 31, 2018: Accounts of Chemical Research
Hailey J Knox, Jefferson Chan
Photoacoustic imaging (PAI) is a powerful imaging modality capable of mapping the absorption of light in biological tissue via the PA effect. When chromophores are optically excited, subsequent energy loss in the form of heat generates local thermoelastic expansion. Repeated excitation from a pulsed laser induces pressure fluctuations that propagate through tissue and can be detected as ultrasound waves. By combining ultrasonic detection with optical excitation, PAI enables high-resolution image acquisition at centimeter depths...
October 31, 2018: Accounts of Chemical Research
Sonja Pullen, Guido H Clever
Porous nanostructures and materials based on metal-mediated self-assembly have developed into a vibrantly studied subdiscipline of supramolecular chemistry during the past decades. In principle, two branches of such coordination compounds can be distinguished: Metal-organic frameworks (MOFs) on the one side represent infinite porous networks of metals or metal clusters that are connected via organic ligands to give solid-state materials. On the other hand, metal-organic cages (MOCs) are discrete and soluble systems with only a limited number of pores...
October 31, 2018: Accounts of Chemical Research
Zibao Gan, Nan Xia, Zhikun Wu
Among many outstanding findings associated with the quantum size effect, one of the most exciting is the discovery of the antigalvanic reaction (AGR), which is the opposite of the classic galvanic reaction (GR) that has a history of nearly 240 years. The GR, named after Italian scientist Luigi Galvani, involves the spontaneous reduction of a noble-metal cation by a less noble metal in solution driven by the difference in electrochemical potentials. Classic galvanic reduction has been widely applied and has recently received particular interest in nanoscience and nanotechnology...
October 31, 2018: Accounts of Chemical Research
Yun-Fei Zhang, Zhang-Jie Shi
Transition-metal catalyzed cross-coupling reactions have emerged as a powerful tool for constructing biaryl compounds. Aryl halides and aryl metallic reagents (typically prepared from aryl halides) are used as coupling partners. It would be desirable to replace either aryl halide or aryl metallic reagents used in cross-couplings reactions with more readily available surrogates. Oxidative dehydrogenative cross-coupling between two different "inert" aryl C-H bonds represents an ideal system that would revolutionize cross-coupling chemistry...
October 30, 2018: Accounts of Chemical Research
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