Chinese Journal of Chemistry最新文献

The pursuit of sustainable and environmentally benign synthetic methods continues to challenge organic chemists. Herein, we introduce a magnetoredox system for tri- and difluoromethylation of isocyanides and N-arylacrylamides using a rotating magnetic field and steel rods. This magnetoredox approach enables facile synthesis of functionalized phenanthridines and oxindoles without the need for catalysts and additives under mild conditions. Such a system potentially represents an attractive strategy for selective formation of bonds through multifaceted regulation of magnetic intensity, rotating frequency, and rod size.

Two families of cyclopentadienyl (Cp)/carboranyl heteroleptic sandwiched organolanthanide complexes, namely [Ln{η⁵:σ-Me₂C(C₅H₄)(C₂B₁₀H₁₀)}₂][Li(DME)₃] (1Ln, Ln = Tb, Dy, Ho, Er) and [2-THF-2'-(μ²-Cl)Li(THF)₃-2,2'-Ln(nido-1,7-C₂B₉H₁₁)Cp*] (2Dy), were synthesized. Family of 1Ln has been proposed based on the mixing-ligands idea by linking Cp and nido-dicarborllide. However, the carborane cage of [Me₂C(C₅H₄)(C₂B₁₀H₁₀)]²⁻ deprotons and forms a mono-C⁻ anion rather than deboron to form dicarborllide dianion. Hence, the family of 1Ln features a dysprosocenium skeleton with extra two coordination of C⁻ anions of carborllides. Such coordination geometry is more like a tetrahedron if abstracting the centroids of two coordinated Cp rings. In this cubic-type geometry, no significant magnetic axiality is presented; only 1Dy and 1Tb show field-induced slow magnetic relaxation behavior below 10 K. Inspired by 1Ln, the free pentamethylcyclopentadienyl (Cp*⁻) and nido-dicarborllide ligands are used to sandwich central Dy³⁺ ion, achieving heteroleptic complex 2Dy. The bending angle by linking the centroid of Cp*⁻, Dy³⁺ and C₂B₃²⁻ in 2Dy is increased to 132.8(1)°. As such, the effective energy barrier for magnetic reversal (U_eff) and magnetic blocking temperature T_B (ZFC) are both increased (U_eff = 616(10) K; T_B = 6 K). The effort of further enhancing U_eff and T_B in such heteroleptic organolanthanide sandwiches should rely on keeping increasing the ligand axiality.

Oil-in-oil nonaqueous emulsions are of great interest for developing emulsion-templated polymers and encapsulation systems that are incompatible with water-sensitive substances. Tailor-made amphiphilic block copolymers are by far the most efficient stabilizers for oil-in-oil emulsions while less attention is given to copolymers with more complex architectures. Here, we report the stabilization of DMSO-silicone oil interface by bottlebrush random copolymers (BRCPs) containing norbornene backbones with densely grafted poly(methyl methacrylate) (PMMA) and polystyrene (PS) side chains. The assembly kinetics of BRCPs at the DMSO-silicone oil interface can be divided into three processes, including diffusion, reconfiguration and reorganization, and can be varied by tuning the degree of polymerization of the backbone (N_B). Due to the high efficiency of BRCPs in reducing the interfacial tension, when using BRCPs as stabilizers, stable silicone oil-in-DMSO traditional emulsions and high internal phase emulsions (HIPEs) can be successfully obtained, while no stable emulsions can be achieved with linear PMMA-b-PS serving as the stabilizer. This study, for the first time, underscores the great potential of amphiphilic bottlebrush copolymers in preparing oil-in-oil emulsions. Given the advances in polymerization strategy, a broad variety of amphiphilic bottlebrush copolymers are expected to be synthesized and applied in the stabilization of nonaqueous biphasic systems.

In on-surface synthesis, dimers are typically utilized to explore reaction mechanisms or as intermediates in the formation of final products. However, constructing the innovative nanostructures with dimers as building blocks remains challenging. Here, using non-planar 2,2′,7,7′-tetrabromo-9,9′-biflurenyliden molecules, we have successfully synthesized dimeric covalent organic frameworks (COFs) on the Au(111) surface through a temperature-controlled cascade reaction. Notably, the H-H steric hindrance within precursors caused by double bonds leads to selective stepwise debromination during the thermal annealing, which promotes the dimerization through intermolecular Ullmann coupling and cyclodehydrogenation reaction to form COFs primarily constituted by dimer building blocks. Combining scanning tunneling microscopy/spectroscopy and density functional theory calculations, we have precisely confirmed the structural evolution and reaction mechanism. Furthermore, by introducing Ag adatoms to form C−Ag−C intermediates, we have successfully regulated the reaction path and synthesized one-dimensional nanoribbons with dimers as building blocks. This work not only validates the strategy of synthesizing dimeric nanostructures on different surfaces through cascade reactions induced by precursor design, but also enriches the research field of surface synthesis of COFs and nanoribbons.

Improving the catalytic efficiency and anti-poisoning ability of Pt-based catalysts is very critical in methanol electrolysis technology for high-purity hydrogen generation. Herein, the nitrogen-doped carbon polyhedrons-encapsulated MoP (MoP@NC) supported Pt nanoparticles were demonstrated to be effective for methanol electrolysis resulting from the combined advantages. The nitrogen-doped carbon polyhedrons not only greatly enhanced the conductivity but also effectively prevented the aggregation of MoP to offer Pt anchoring sites. The electronic structure modification of Pt from their interaction reduced the adsorption energy of CO*, resulting in good CO-poisoning resistance and accelerated reaction kinetics. Specifically, Pt-MoP@NC exhibited the highest peak current density of 106.4 mA·cm^–2 for methanol oxidation and a lower overpotential of 28 mV at 10 mA·cm^–2 for hydrogen evolution. Energy-saving hydrogen production from methanol electrolysis was demonstrated in the two-electrode systems assembled by Pt-MoP@NC which required a low cell voltage of 0.65 V to reach a kinetic current density of 10 mA·cm^–2 on the glass carbon system, about 1.02 V less than that of water electrolysis.

Salimabromide, a unique and scarce marine tetracyclic polyketide, was synthesized in both racemic and optically active forms. A novel carboxylic acid-directed method for tandem oxidative difunctionalization of olefins was developed, whereby the formation of bridged butyrolactone and enone moieties occurs concurrently. Density functional theory (DFT) calculations indicate that this reaction follows a [3+2] process rather than the [2+2] process. In the meantime, the distinctive benzo-fused [4.3.1] carbon skeleton and highly hindered vicinal quaternary stereocenters were simultaneously constructed through a challenging intramolecular Giese-Baran radical cyclization. Furthermore, deuterium kinetic isotopic effects were utilized to enhance the efficacy of this pivotal step. This represents a new illustration of the application of kinetic isotope effects in natural product synthesis. Then, the short asymmetric synthesis of (+)-salimabromide (13 or 15 steps) was accomplished by combing this method with rhodium-catalyzed enantioselective hydrogenation of a cycloheptenone derivative (97% ee) or conjugate addition of an aryl boronic acid with 2-cyclohepten-1-one (> 99% ee).

Spin crossover (SCO), characterized by distinct high-spin (HS) and low-spin (LS) states, has potential applications in memory, electronic, and electroluminescent devices. The OFF/ON switching of SCO is crucial for obtaining bistable magnetic properties. However, there are few strategies for achieving this switching. Herein, based on a ligand chemical doping strategy, we report an Fe(III) solid solution that can be prepared using a ligand chemical doping strategy, enabling not only the OFF/ON switching of SCO but also the fine-tuning of the spin transition temperature (T_c) within a 45 K range near room temperature. The experimental results show that when the polar ligand doping ratio reaches 20%, SCO behavior is triggered, and the crystal phase transforms significantly, becoming loose and flexible. Furthermore, T_c can be continuously regulated as the ligand-doping ratio increases. Density functional theory (DFT) calculations reveal that solid packing-induced molecular distortion blocks SCO, whereas loosely flexible packing triggers SCO via fluorinated ligand chemical doping.

Enhancing the DNA toolbox with innovative photochemical reactions is pivotal for advancing nucleic acid-based technologies. Aldehyde groups, versatile bioorthogonal handles for imine formation under acidic conditions, are particularly valuable due to their roles in nucleic acid epigenetics. Here, we present the first photocatalytic on-DNA aldehyde allylation, enabling precise DNA functionalization under mild, neutral aqueous conditions. Our approach utilizes a photocatalytic polarity-reversal reaction between DNA-conjugated benzaldehydes and allyl sulfones. This reaction demonstrates exceptional chemoselectivity while preserving DNA integrity. By varying allyl sulfones, we achieve site-specific labeling of non-native DNA with the aldehyde group and cross-linking with DNA-bearing allyl sulfones. Furthermore, our method facilitates selective labeling and pull-down enrichment of 5-formylpyrimidine nucleotides among complex cellular DNA. This photocatalytic on-DNA aldehyde transformation expands the limited bioorthogonal photochemical toolboxes, providing novel avenues for functionalizing both non-native and native aldehyde modifications on DNA.