Site-specific fluorescent labeling approaches for naringenin, an essential flavonone in plant nitrogen-fixation signaling pathways

In search of an appropriate position for the fluorescent labeling, six chemically available positions of the flavonone core of naringenin have been examined. A number of azido-containing naringenin derivatives were accordingly prepared in various site-specific fashions, and the mild Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition successfully served as the common "Click" labeling tool in the final steps. On the basis of the biological activities of the first batch of labeled compounds, further optimization at the C-6 position of naringenin finally afforded naringenin-flu (27), which acquired 20% of the potency of naringenin and presented good optical properties. Entry of naringenin-flu into living Rhizobium cells was demonstrated by in vitro fluorescent imaging experiments.     

Synthesis and structures of binuclear half-sandwich cobalt (III) ortho-carboranedithiolato complexes with silyl-bridged bis(cyclopentadienyl) ligands

Five binuclear half-sandwich cobalt complexes, [(η⁵-C₅H₄)Co(CO)I₂]₂SiMe₂ (3), [(η⁵-C₅H₄)Co(S₂C₂B₁₀H₁₀)]₂SiMe₂ (4), [(η⁵-C₅H₄)]₂Co₂(μ₂-S₂C₂B₁₀H₁₀)SiMe₂ (5), [(η⁵-C₅H₃)CoI₂](μ-I)[(η⁵-C₅H₃)Co(CO)I](SiMe₂)₂ (8), [(η⁵-C₅H₃)Co(S₂C₂B₁₀H₁₀)]₂(SiMe₂)₂ (9), were successfully synthesized in moderate yield by the reactions of corresponding ligands, (C₅H₅)₂SiMe₂ (1) and (C₅H₄)₂(SiMe₂)₂ (6), respectively. The molecular structures of 3, 5, 6, 8 and 9 was determined by X-ray crystallographic analysis, which distinctly depict various molecular structures containing the Cp rings and the metal centers with halide or 1,2-dicarba-closo-dodecaborane-1,2-dithiolato ligands. For the (η⁵-C₅H₄)₂SiMe₂ complexes, coordination of the fragments CpCo favors a exo conformation. With the rigid structure of the di-bridged ligand (C₅H₄)₂(SiMe₂)₂, only cis isomers of the corresponding (η⁵-C₅H₃)₂(Si₂Me₂)₂ complexes are formed. All the complexes have been well characterized by elemental analysis, NMR and IR spectra.     

Asymmetric Total Synthesis of Hasubanan Alkaloids: Periglaucines A–C,N,O-Dimethyloxostephine and Oxostephabenine

We report herein the asymmetric total synthesis of periglaucines A–C, N,O-dimethyloxostephine and oxostephabenine. The key strategies used include: 1) a Rh^I-catalyzed regio- and diastereoselective Hayashi-Miyaura reaction to connect two necessary fragments; 2) an intramolecular photoenolization/Diels–Alder (PEDA) reaction to construct the highly functionalized tricyclic core skeleton bearing a quaternary center; 3) a bio-inspired intramolecular Michael addition and transannular acetalization to generate the aza[4.4.3]propellane and the tetrahydrofuran ring.     

高比能锂离子电池层状富锂正极材料改性策略研究进展

层状富锂材料具有超过250 mAh∙g⁻¹的高可逆比容量,被认为是下一代高比能锂离子电池最具商业化前景的正极材料之一。然而,层状富锂材料在实际应用之前仍需解决诸多挑战,如高电压氧释放、层状到岩盐相的结构变化、过渡金属离子迁移等结构劣化,并由此带来了较低的初始库伦效率、电压/容量的衰减以及循环寿命的不足。针对以上问题,进行层状富锂材料改性无疑是一种行之有效的方法。本综述全面介绍了层状富锂材料的结构、组分以及电化学性能,在此基础上对材料改性策略进行了系统阐述,详细介绍了体相掺杂、表面包覆、缺陷设计、离子交换和微结构调控等一系列改性策略的现状以及发展趋势,最终提出了高容量和长循环层状富锂材料和高比能锂离子电池的设计思路。     

A Compartmentalized Nanoreactor Formed by Interfacial Hydrogelation for Cascade Enzyme Catalytic Therapy

Some cellular enzymatic pathways are located within a single organelle, while most others involve enzymes that are located within multiple compartmentalized cellular organelles to realize the efficient multi-step enzymatic process. Herein, bioinspired by enzyme-mediated biosynthesis and biochemical defense, a compartmented nanoreactor (Burr-NCs@Gl^SOD) was constructed through a self-confined catalysis strategy with burr defect-engineered molybdenum disulfide/Prussian blue analogues (MoS₂/PBA) and an interfacial diffusion-controlled hydrogel network. The specific catalytic mechanism of the laccase-like superactivity induced hydrogelation and cascade enzyme catalytic therapy were explored. The confined hydrogelation strategy introduces a versatile means for nanointerface functionalization and provides insight into biological construction of simulated enzymes with comparable activity and also the specificity to natural enzymes.     

Fused Indacene Dimers

Polycyclic hydrocarbons consisting of two or more directly fused antiaromatic subunits are rare due to their high reactivity. However, it is important to understand how the interactions between the antiaromatic subunits influence the electronic properties of the fused structure. Herein, we present the synthesis of two fused indacene dimer isomers: s-indaceno[2,1-a]-s-indacene ( s -ID ) and as-indaceno[3,2-b]-as-indacene ( as -ID ), containing two fused antiaromatic s-indacene or as-indacene units, respectively. Their structures were confirmed by X-ray crystallographic analysis. ¹H NMR/ESR measurements and DFT calculations revealed that both s -ID and as -ID have an open-shell singlet ground state. However, while localized antiaromaticity was observed in s -ID , as -ID showed weak global aromaticity. Moreover, as -ID exhibited a larger diradical character and a smaller singlet-triplet gap than s -ID . All the differences can be attributed to their distinct quinoidal substructures.     

Formation of a three-dimensional bispyridyl based metal-organic architecture containing unique Ag...Ag （d^10-d^10） interactions

A novel co-ordination polymer based on IB metal thiocyanates, [Ag2（NCS）2（4,4＇-bipy）]. （1）（4,4＇-bipy = 4,4＇-bispyridine）, has been synthesized by the pre-assembly method and characterized by X-ray crystallography. The complex exists as a three- dimensional network consisting of （AgSCN）. undulating layers linked by 4,4＇-bipy bridges.     

LIBS技术在土壤重金属污染快速测量中的应用

激光诱导击穿光谱(laser-induced breakdown spectroscopy,LIBS)作为一种很有前景的分析和测量技术在过去的10多年中已经显现出来.本文介绍了激光诱导击穿光谱的工作原理和定量定性分析的理论基础,综述了LIBS技术在土壤重金属As、Cd、Cr、Hg、Pb 和Zn等污染快速测量中的应用和仪器研究进展,分析了LIBS应用在该领域中存在的主要问题,对未来基于LIBS快速检测土壤重金属污染需要解决的定量测量和检测限等关键问题进行了探讨.     

Synthesis of Carbon Nanofibers for Mediatorless Sensitive Detection of NADH

Highly sensitive amperometric detection of dihydronicotinamide adenine dinucleotide (NADH) by using novel synthesized carbon nanofibers (CNFs) without addition of any mediator has been proposed. The CNFs were prepared by combination of electrospinning technique with thermal treatment method and were applied without any oxidation pretreatment to construct the electrochemical sensor. In amperometric detection of NADH, a linear range up to 11.45 μM with a low detection limit of 20 nM was obtained with the CNF‐modified carbon paste electrode (CNF‐CPE). Good selectivity was exhibited for the simultaneous detection of NADH and its common interferent of ascorbic acid (AA) by differential pulse voltammogram. The attractive electrochemical performance and the versatile preparation process of the CNF‐CPE made it a promising candidate for designing effective NADH sensor.     

Synthesis, crystal structure, and optical properties of a novel rare-earth complex Nd(C2F5COO)3 · Phen

A novel neodymium pentafluoropropionate binuclear complex, Nd(C₂F₅COO)₃ · Phen (Phen: 1,10-phenanthroline), was synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, FT-IR spectra, UV–Vis–NIR absorption, and PL spectra. Single-crystal data show that the complex bears centrosymmetric dinuclear structure with a planar ligand configuration. Four carboxylato groups act as η²-chelate-μ²-carboxylato-k¹O:k¹O′-bridge-ligands, the other two occupy the terminal position as monodentate ligands. At the same time, the C–O distances appear averaged which indicate the three atoms of carboxylato forming electron-conjugate system. Hydrogen bond and π–π-stacking link the binuclear to two-dimensional sheet. Optical spectra exhibit the complex possesses typical Nd(III) ion absorption and photoluminescence emission.