A New Carotane Sesquiterpenoid Derivative with Antifungal Activity from Gymnopus sp. 0612-9

Chemistry of Natural Compounds - A new carotane sesquiterpenoid, methyl gymnabloate (1), was isolated from the fermentation broth of the wild macrofungus Gymnopus sp. 0612-9. Its structure was...     

Chemical Synthesis and Immunological Evaluation of a Pentasaccharide Bearing Multiple Rare Sugars as a Potential Anti-pertussis Vaccine

With the infection rate of Bordetella pertussis at a 60-year high, there is an urgent need for new anti-pertussis vaccines. The lipopolysaccharide (LPS) of B. pertussis is an attractive antigen for vaccine development. With the presence of multiple rare sugars and unusual glycosyl linkages, the B. pertussis LPS is a highly challenging synthetic target. In this work, aided by molecular dynamics simulation and modeling, a pertussis-LPS-like pentasaccharide was chemically synthesized for the first time. The pentasaccharide was conjugated with a powerful carrier, bacteriophage Qβ, as a vaccine candidate. Immunization of mice with the conjugate induced robust anti-glycan IgG responses with IgG titers reaching several million enzyme-linked immunosorbent assay (ELISA) units. The antibodies generated were long lasting and boostable and could recognize multiple clinical strains of B. pertussis, highlighting the potential of Qβ-glycan as a new anti-pertussis vaccine.     

Nb(iPrNPMe2)3Fe–PMe3: A potential high reactivity heterobimetallic catalyst for acetylene cycloadditions

Alkynes cycloaddition reactions are powerful tools for constructing cyclic molecules with optimal atom efficiency, but these reactions cannot proceed at ambient temperature without transition-metal catalysts. In this work, a heterobimetallic complex featuring an Nb–Fe triple bond, Nb(ⁱPrNPMe₂)₃Fe–PMe₃, has been evaluated as the potential catalyst for acetylene cycloaddition, using density functional theory. The calculated results show that the singlet-state (i.e. ground-state) Nb(ⁱPrNPMe₂)₃Fe–PMe₃ can be applied to benzene synthesis, but is not suitable for cyclobutadiene. Benzene can be obtained easily at room temperature and is the unique product on the singlet potential surface. The irradiation of infrared-red light can drive the excitation of singlet Nb(ⁱPrNPMe₂)₃Fe–PMe₃ to its triplet state. Both benzene and cyclobutadiene can be formed on the triplet reaction potential surface due to their low energy barriers. Therefore, Nb(ⁱPrNPMe₂)₃Fe–PMe₃ is a potential high reactivity heterobimetallic catalyst for the cyclotrimerization of alkynes. In the reaction process, the catalytic active site of Nb(ⁱPrNPMe₂)₃Fe–PMe₃ moves from niobium to iron.     

表面喷砂对有机玻璃沿面闪络性能影响

绝缘子表面粗糙处理是提升其沿面闪络性能的重要途径,表面粗糙化处理方式不当,极易带来表面结构不均匀,难以获得稳定耐压性能的绝缘材料。为提升绝缘子表面粗糙处理的均匀性,本文利用表面喷砂技术对圆柱形有机玻璃(PMMA)绝缘子进行了粗糙化处理研究,以球形二氧化硅(SiO2)颗粒为工作介质,研究了不同喷砂粒径、氢氟酸后处理等因素对绝缘材料表面形貌和组分的影响,并利用短脉冲高压测试平台对喷砂处理前后有机玻璃绝缘子样品进行了真空沿面闪络性能测试。研究结果表明,喷砂处理在有机玻璃表面形成了较为均匀的凹坑,HF酸能够有效去除表面残留的SiO2颗粒,具有表面喷砂粗糙结构的绝缘子沿面闪络电压得到了稳定提升,相较于未处理的绝缘子闪络电压提升了约80%。     

Recent Advances of Freestanding Cathodes for Li-S Batteries

Lithium-sulfur batteries (LSBs) with high energy density and low cost have been recognized as one of the most promising next-generation energy storage systems. Although it has taken decades of development, the practical application of LSBs has been hindered by several inherent obstacles, particularly the severe shuttle effect and sluggish reaction kinetics in the sulfur cathode. Various strategies have been proposed to address these problems via rational design of electrode materials and configurations. Freestanding sulfur cathode could be a promising strategy to improve the sulfur mass loading at the cathode level and energy density of LSBs. This minireview will briefly summary the recent advances in freestanding cathodes for LSBs. The advantages and disadvantages of various freestanding cathodes are discussed and the prospects for the development of flexible cathodes are envisioned.     

Polyhydrido Copper Nanoclusters with a Hollow Icosahedral Core: [Cu30H18{E2P(OR)2}12] (E=S or Se; R=nPr,iPr or iBu)

Although atomically precise polyhydrido copper nanoclusters are of prime interest for a variety of applications, they have so far remained scarce. Herein, this work describes the synthesis of a dithiophosphate-protected copper(I) hydride-rich nanocluster (NC), [Cu₃₀H₁₈{S₂P(OnPr)₂}₁₂] ( 1_H ), fully characterized by various spectroscopic methods and single-crystal X-ray diffraction. The X-ray structure of 1_H reveals an unprecedented central Cu₁₂ hollow icosahedron. Six faces of this icosahedron are capped by Cu₃ triangles, the whole Cu₃₀ core being wrapped by twelve dithiophosphate ligands and the whole cluster has ideal S₆ symmetry. The locations of the 18 hydrides in 1_H were ascertained by a single-crystal neutron diffraction study. They are composed of three types: capping μ₃-H, interstitial μ₄-H (seesaw) and μ₅-H ligands (square pyramidal), in good agreement with the DFT simulations. The numbers of hydrides and ligand resonances in the ¹H NMR spectrum of 1_H are in line with their coordination environment in the solid state, retaining the S₆ symmetry in solution. Furthermore, two new Se-protected polyhydrido copper nanoclusters, [Cu₃₀H₁₈{Se₂P(OR)₂}₁₂] ( 2_H : R=iPr 3_H : R=iBu) were synthesized from their sulfur relative 1_H via ligand displacement reaction and their X-ray structures feature the exceptional case where both the NC shape and size are fully conserved during the course of ligand exchange. DFT and TD-DFT calculations allow understanding the bonding and optical properties of clusters 1_H – 3_H . In addition, the reaction of 1_H with [Pd(PPh₃)₂Cl₂] in the presence of terminal alkynes led to the formation of new bimetallic Cu−Pd alloy clusters [PdCu₁₄H₂{S₂P(OnPr)₂}₆(C≡CR)₆] ( 4 : R=Ph; 5 : R = C₆H₄F).     

Tuning the Triplet Excited State of Bis(dipyrrin) Zinc(II) Complexes: Symmetry Breaking Charge Transfer Architecture with Exceptionally Long Lived Triplet State for Upconversion

Zinc(II) bis(dipyrrin) complexes, which feature intense visible absorption and efficient symmetry breaking charge transfer (SBCT) are outstanding candidates for photovoltaics but their short lived triplet states limit applications in several areas. Herein we demonstrate that triplet excited state dynamics of bis(dipyrrin) complexes can be efficiently tuned by attaching electron donating aryl moieties at the 5,5′-position of the complexes. For the first time, a long lived triplet excited state (τ_T=296 μs) along with efficient ISC ability (Φ_Δ=71 %) was observed for zinc(II) bis(dipyrrin) complexes, formed via SBCT. The results revealed that molecular geometry and energy gap between the charge transfer (CT) state and triplet energy levels strongly control the triplet excited state properties of the complexes. An efficient triplet–triplet annihilation upconversion system was devised for the first time using a SBCT architecture as triplet photosensitizer, reaching a high upconversion quantum yield of 6.2 %. Our findings provide a blueprint for the development of triplet photosensitizers based on earth abundant metal complexes with long lived triplet state for revolutionary photochemical applications.     

Stereoselectivity and nonmigratory insertion mechanism of dimethylacetylene dicarboxylate into metallocene-hydride of Cp2M(L)H [Cp = η5-C5H5; M = Nb,V; L = CO,P (OMe)3]: A DFT study

The insertion of an alkyne into transition metal–hydrogen bonds is a key elementary step in catalytic polymerization and hydrogenation processes. It was found that a (Z)- or (E)-type alkyenyl complex can be formed through trans/cis stereospecific processes. In this work, the reaction mechanism of Cp₂M(L)H [Cp = η⁵-C₅H₅; M = Nb, V; L = CO, P (OMe)₃] with dimethylacetylene dicarboxylate (DMAD), and the factors influencing the stereoselectivity have been investigated based on density functional theory calculations. The calculated results show that all of the reactions are exothermic. For L = CO, the Z-isomer product forms first even at low temperatures because of the low Gibbs free energy barrier (ΔG^#). Then the Z-pro converts to E-pro , while for L = P (OMe)₃, the exclusive product is the E-isomer. For different metal centers, the reaction mechanisms of the Cp₂M(CO)H + DMAD (M = Nb and V) reaction are similar, while their products are different at room temperature. For M = Nb, because the energy barrier of the isomerization from Z-pro to E-pro is low and the relative free energies of Z-pro and E-pro are almost equal, both Z-pro and E-pro can be obtained. While for the Cp₂V(CO)H + DMAD reaction, only the Z-pro can be obtained under mild conditions, E-pro can be obtained only at high temperatures. For the Cp₂M(CO)H+DMAD(M=V and Nb) reactions, the formation of E-isomer products proceeds via two five-membered ring transition states. The calculated results provide an reasonable explanation for the experimental results and predict a new insertion reaction.     

Stereodivergent Desymmetrization of Simple Dicarboxylates via Branch-Selective Pd/Cu Catalyzed Allylic Substitution

Asymmetric desymmetrization has been demonstrated to be a powerful strategy for building stereocenters in asymmetric synthesis. Herein, a Pd/Cu catalyzed asymmetric desymmetrization reaction with a simple geminal dicarboxylate is reported. A wide scope of imino esters bearing an aryl or heteroaromatic group were compatible with this bimetallic catalytic system. The reactions proceeded smoothly, giving the desired products in good yields with high to excellent regio-, diastereo-, and enantioselectivity (up to 20 : 1 branched:linear, >20 : 1 dr, >99 % ee). Notably, the reaction favored branched selectivity, which is unusual for the Pd-catalyzed allylic alkylation reaction. In addition, the standard product could be easily transformed to other valuable molecules such as chiral allylic alcohols, carbamates, and organic boron compounds. Furthermore, DFT calculations were conducted to explain the origin of the branched selectivity.     

Assembled synthesis of luminescent mono/double‐layered 2D and 3D Zn (II)‐based coordination polymers tuned by flexible bis (pyridyl)propane‐1,2‐diamines and diverse organic dicarboxylates

Six mono/double‐layered 2D and three 3D coordination polymers were synthesized by a self‐assembly reaction of Zn (II) salts, organic dicarboxylic acids and L1/L2 ligands. These polymeric formulas are named as [Zn(L1)(C₄H₂O₄)_0.5 (H₂O)]_n·0.5n(C₄H₂O₄)·2nH₂O ( 1 ), [Zn₂(L2)(C₄H₂O₄)₂]_n·2nH₂O ( 2 ), [Zn(L1)(m‐BDC)]_n ( 3 ), [Zn₂(L2)(m‐BDC)₂]_n·2nH₂O ( 4 ), [Zn₃(L1)₂(p‐BDC)₃(H₂O)₄]_n·2nH₂O ( 5 ), [Zn₂(OH)(L2) (p‐BDC)_1.5]_n ( 6 ), [Zn₂(L1)(p‐BDC)₂]_n·5nH₂O ( 7 ), [Zn₂(L2)(p‐BDC)₂]_n·3nH₂O ( 8 ) and [Zn₂(L1)(C₄H₄O₄)_1.5(H₂O)]_n·n(ClO₄)·nH₂O ( 9 ) [L1 = N,N′‐bis (pyridin‐4‐ylmethyl)propane‐1,2‐diamine, L2 = N,N′‐bis (pyridin‐3‐ylmethyl)propane‐1,2‐ diamine, m‐BDC^2? = m‐benzene dicarboxylate, p‐BDC^2? = p‐benzene dicarboxylate]. Meanwhile, these polymers have been characterized by elemental analysis, infrared, thermogravimetry (TG), photoluminescence, powder and single‐crystal X‐ray diffraction. Polymers 1–6 present mono‐ and double (4,4)‐layer motifs accomplished by L1/L2 ligands with diverse conformations and organic dicarboxylates, and the layer thickness locates in the range of 5.8–15.0 Å. In three 3D polymers, the L1 and L2 molecules adopt the same cis‐conformations and join adjacent Zn (II) cations together with p‐BDC^2? or succinate, giving rise to different binodal (4,4)‐c nets with (4.5².8³)(4.5³.7²) ( 7 ), pts ( 8 ) topology and twofold interpenetrated binodal (5,5)‐c nets with (3².4⁴.5².6²)(3.4³.5².6⁴) ( 9 ). Therefore, the diverse conformations of the two bis (pyridyl)‐propane‐1,2‐diamines and the feature of different organic dicarboxylate can effectively influence the architectures of these polymers. Powder X‐ray diffraction patterns demonstrate that these bulk solid polymers are pure phase. TG analyses indicate that these polymers have certain thermal stability. Luminescent investigation reveals that the emission maximum of these polymers varies from 402 to 449 nm in the solid state at room temperature. Moreover, 1 , 3 and 5–8 show average luminescence lifetimes from 8.81 to 16.30 ns.