An electrochemical C–H acylation of electron-deficient N-heteroarenes with α-keto acids is reported. This first electrochemical Minisci acylation reaction proceeded using NH4I as a redox catalyst. A ...broad N-heteroarene scope and high functional group tolerance are observed. Selective monoacylation of N-heteroarenes is achieved via control of acyl radical at a low concentration. The results of cyclic voltammetry and control experiments disclose that the electrogenerated I2 is likely the active species to initiate the oxidative decarboxylation of carboxylate anion via an acyl hypoiodite intermediate. The electrochemical Minisci acylation provides a straightforward approach for the late-stage functionalization of pharmacophores.
An electrochemical oxidative addition of sulfonamides and imide to allyl sulfones was developed for the facile synthesis of synthetically useful allylamines. This method avoids the use of transition ...metal catalysts and additional bases, which are commonly used for the synthesis of allylamines. Moreover, cheap and easily available NaI was employed as the mediator without use of an external supporting electrolyte. Radical trapping experiments showed that nitrogen‐centered radicals were involved in these transformations.
Ferromagnetism is usually deemed incompatible with superconductivity. Consequently, the coexistence of superconductivity and ferromagnetism is usually observed only in elegantly designed ...multi-ingredient structures in which the two competing electronic states originate from separate structural components. Here we report the use of surface molecular adsorption to induce ferromagnetism in two-dimensional superconducting NbSe2, representing the freestanding case of the coexistence of superconductivity and ferromagnetism in one two-dimensional nanomaterial. Surface-structural modulation of the ultrathin superconducting NbSe2 by polar reductive hydrazine molecules triggers a slight elongation of the covalent Nb-Se bond, which weakens the covalent interaction and enhances the ionicity of the tetravalent Nb with unpaired electrons, yielding ferromagnetic ordering. The induced ferromagnetic momentum couples with conduction electrons generating unique correlated effects of intrinsic negative magnetoresistance and the Kondo effect. We anticipate that the surface molecular adsorption will be a powerful tool to regulate spin ordering in the two-dimensional paradigm.
Conspectus Understanding special stability of numerous ligand-protected gold nanoclusters has always been an active area of research. In the past few decades, several theoretical models, including ...the polyhedral skeletal electron pair theory (PSEPT), superatom complex (SAC), and superatom network (SAN), among others, have been developed for better understanding the stabilities and structures of selected ligand-protected gold nanoclusters. This Account overviews the recently proposed grand unified model (GUM) to offer some new insights into the structures and growth mechanism of nearly all crystallized and predicted ligand-protected gold nanoclusters. The main conceptual advancement of the GUM is identification of the duet and octet rules on the basis of the “big data” of 70+ reported ligand-protected gold nanoclusters. According to the two empirical rules, the cores of the gold nanoclusters can be regarded as being composed of two kinds of elementary blocks (namely, triangle Au3 and tetrahedron Au4), each having 2e closed-shell valence electrons (referred as Au3(2e) and Au4(2e)), as well as the secondary block (icosahedron Au13) with 8e closed-shell valence electrons (referred as Au13(8e)). The two elementary blocks (Au3(2e) and Au4(2e)) and the secondary block (Au13(8e)), from electron counting point of view, can be regarded as an analogy of the highly stable noble-gas atoms of He and Ne, respectively. In each elementary block, the Au atoms exhibit three different valence-electron states (i.e., 1e, 0.5e, and 0e), depending on the type of ligands bonded with these Au atoms. Such three valence-electron states are coined as three “flavors” of gold (namely, bottom, middle, and top “flavor”), a term borrowed from the quark model in the particle physics. Upon application of the duet and octet rules with accounting the three valence states of gold atoms, the Au3(2e), Au4(2e), and Au13(8e) blocks can exhibit 10 (denoted as Δ1–Δ10), 15 (denoted as T1–T15), and 91 (denoted as I1–I91) variants of valence states, respectively. When packing these blocks (with distinct electronic states) together, it forms the gold core of ligand-protected gold nanocluster. As such, the special stabilities of the ligand-protected gold nanoclusters are explained based on the local stability of each block. With GUM, rich and complex structures of ligand-protected gold nanoclusters have been analyzed through structure anatomy. Moreover, the growth of these clusters can be simply viewed as sequential addition of the blocks, rather than as addition of the gold atoms. Another useful application of the GUM is to analyze the structural isomerism. The three types of isomerism for the gold nanoclusters, i.e., core, staple, and complex isomerism, can be considered as an analogy of chain, point, and functional isomerism (known in organic chemistry), respectively. GUM can be applied to predict new clusters, thereby guiding experimental synthesis. Indeed, a number of ligand-protected gold nanoclusters with high stabilities were rationally designed based on the GUM.
Efficient electrocatalytic aziridination of alkenes has been achieved for the first time. A structurally broad range of aziridines was easily accessed using an undivided cell operated at constant ...current and mediated by a catalytic quantity of n-Bu4NI. The electrocatalytic reaction also proceeded in the absence of additional conducting salt. The aziridination is proposed to follow a radical mechanism.
The material should be in harmony with the environment during its life cycle. This article reviews the origin, concept, research status and application prospects of eco-environmental materials, ...discusses the environmental coordination evaluation methods of eco-environmental materials, discusses the principles and methods of environmental coordination design of various materials, and lists several typical examples of research on eco-environmental materials. It focuses on the separation and removal of impurities during the alloy regeneration cycle, as well as the organic polymer regeneration cycle technology. In this regard, this article conducts a series of analyses on the development trend of ecological environment materials.
A tightly coupled integrated navigation system (TCINS) for hypersonic vehicles is proposed when the satellite signals are disturbed. Firstly, the architecture of the integrated navigation system for ...the hypersonic vehicle is introduced. This system applies fiber SINS, BeiDou satellite receiver (BDS) and System On a Parogrammable Chip (SOPC) missile-born computer. Subsequently, the SINS mechanization for hypersonic vehicle is presented. The J2 model is employed for the normal gravity of the near space. An algorithm for updating the attitude, velocity and position is designed. State equations and measurement equations of SINS/BDS tightly coupled integrated navigation for hypersonic vehicle are given, and a scheme of validity for satellite data is designed. Finally, the SINS/BDS tightly coupled vehicle field tests and hardware-in-the-loop (HWIL) simulation tests are carried out. The vehicle field test and HWIL simulation results show that the heading angle error of tightly coupled integrated navigation is within 0.2°, the pitch and roll angle errors are within 0.05°, the maximum velocity error is 0.3 m/s, and the maximum position error is 10 m.
An electrochemical strategy for the efficient synthesis of 2‐substituted benzoxazoles was developed using a catalytic amount of sodium iodide (NaI) as a redox catalyst in a two‐phase buffer system.
In this paper, a high resolution, high precision and ultra-low power consumption time-to-digital converter (TDC) is presented. The proposed TDC is based on the gateable Vernier ring oscillator ...architecture. Fine resolution is achieved through two ring oscillators arranged in the Vernier configuration. This TDC employs a single-transition end-of-conversion detection circuit and turns off the ring oscillators whenever the conversion is completed to reduce power consumption. The prototype chip is fabricated in a standard 130 nm digital CMOS process and its area is only 0.03 mm 2 . Using a 1.2 V supply, the TDC achieves a resolution of 7.3 ps, a single-shot precision of 1.0LSB, and an average power consumption of 1.2 mW. A root-mean-square integral nonlinearity (INL) of 1.2 LSB is obtained with the help of an INL look-up-table calibration. Compared to previously reported ring-oscillator based TDCs, the proposed design achieves the lowest power consumption to date.
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