Chinese Journal of Chemistry最新文献

Organic materials have obtained unprecedented attention as emerging electrodes for sodium-ion batteries (SIBs), but they suffer from poor cycling stability and rate performance. Herein, we develop a simple strategy via locking the coplanarity to tune the electron and ion transport in linear polyimide for sodium-ion batteries. From unlocked and flexible molecular chain to spatially locked molecular chain, the polyimide cathodes possess better structural stability and higher electronic conductivity, exhibiting better cycling stability and higher reversible capacity. Moreover, the locked-in coplanar conformation endows the polyimide cathode with large surface area and rich porosity, leading to a rapid ion transport, which synergizes with the good electronic conductivity to improve the rate performance of the SIBs. As a result, the optimized polyimide electrode displays high capacity retentions of 99% after 100 cycles at 50 mA·g^–1 and 100% after 3000 cycles at 1000 mA·g^–1. This work expands the palette to design organic electrodes for high-performance SIBs.

A practical photoinitiated synthetic method for the site-selective γ - and α-chlorination of C(sp³)–H bonds of ketones, (E)-1,3-enones, and alkylbenzenes by chloramine-T (CAT) and N-chlorosuccinimide (NCS) under blue LED (λ_max = 456 nm) light irradiation is reported. Mechanistic studies suggest the reaction to proceed via a radical pathway where the chlorination reagent dichloramine-T (DCT) is generated in situ from the reaction of CAT with NCS. Its premised controlled formation along with that of the carbon-centered radical species derived from the substrate is thought to contribute to product site-selectivity. The developed protocol operates under mild reaction conditions at room temperature and demonstrates excellent functional group tolerance as exemplified by the site-selective γ-C(sp³)–H bond chlorination of carboxylic esters and amides, and late-stage functionalization of several bioactive natural products and drug molecules. The study also highlights the potential of CAT for the first time as a versatile and controllable chlorine radical atom source for site-selective halogenation reactions, expanding its synthetic utility beyond traditional applications.

The origin of a transformation's stereoselectivity is one of the core issues in asymmetric catalysis. Herein, we propose a general competitive induction model for predicting stereoselectivity in dual transition-metal-NHC asymmetric catalysis. This model is demonstrated to explore the origin of stereoselectivity for the asymmetric synthesis of spirooxindoles by Cu(I)/NHC-catalysed [3+3] annulation. Computational studies suggest a mechanism involving deprotonation, Brønsted-acid-assisted decarboxylation, nucleophilic addition, cyclic esterification, and protonation. Our studies suggest that nucleophilic addition is the reversible stereocenter-generating step, while subsequent irreversible cyclic esterification is the stereoselectivity-determining step. The metal-coordinated chiral NHC ligand and the NHC organocatalyst work together to induce chirality in the stereocenter-generating step. In the subsequent stereoselectivity-determining step, the NHC ligand is innocent due to its long distance from the reaction site. Thus, the stereoselectivity is fully determined by the NHC organocatalyst. This constitutes a significant difference from the widely proposed synergistic induction model. This competitive induction model elucidates how the two chiral sources govern stereoselectivity in the stereocenter-generating and stereoselectivity-determining steps, providing valuable insights for the rational design of cooperative asymmetric catalyst systems.

Direct C(sp³)−H alkylation of alkylpyridines provides an efficient route to C(sp³)-rich pyridine motifs, which are highly prevalent in pharmaceuticals and agrochemicals. While numerous ionic methods have been developed, they typically require strong bases, elevated temperatures, or pre-functionalized substrates. To circumvent these limitations, photocatalytic methods relying on radical reactions have emerged, however, pre-activation of the substrates is required or the olefin scope is limited. Here, we report a visible light photocatalytic strategy for pyridylic C(sp³)−H alkylation via in situ borane exchange between pyridine substrates and triphenylphosphine-borane. This method operates under mild conditions, avoids the need for strong bases or metal catalysts, and accommodates both styrenes and unactivated olefins as coupling partners. Mechanistic studies revealed that borane exchange enhances the acidity of the C(sp³)−H bonds, thereby enabling rapid deprotonation to form a pyridylic carbanion intermediate. Subsequent single-electron oxidation by the oxidized form of the photocatalyst (PC) then generates the key pyridylic radical intermediate, which adds to olefins to generate another carbon-centered radical. Final hydrogen atom transfer from an arylthiol affords the desired product in good yields.

Two-dimensional conductive metal–organic frameworks (2D c-MOFs), constructed by coordination between metal ions and π-conjugated ligands, represent a unique class of materials that combine intrinsic porosity and electrical conductivity. However, the contribution of metal nodes to the overall electrical properties remains unclear. In this work, we systematically investigate the role of metal centers on a series of six highly crystalline hexahydroxytriphenylene (HHTP) based c-MOFs, M-HHTP, which incorporate alkaline earth including magnesium and calcium, as well as transition metals including cobalt, nickel, copper, and zinc. Comprehensive structural characterizations reveal that while all M-HHTP frameworks adopt a general honeycomb lattice, however, subtle variations in stacking patterns and coordination environments are induced by different metal ions. Electrical measurements show a pronounced dependence of conductivity on the nature of the metal nodes, in which the conductivity differs by four orders of magnitude due to the difference in metal centers. Furthermore, non-contact terahertz spectroscopy combined with theoretical calculations suggests that in alkaline earth metal-based MOFs, charge transport may proceed via a through-space hopping mechanism between organic ligands. This study elucidates the critical role of metal centers in governing charge transport in M-HHTP MOFs and offers valuable guidance for the rational design of high-performance 2D conductive frameworks.

Conventional lithium-ion batteries that utilize high melting point ethylene carbonate (EC) solvent and graphite anodes exhibit a narrow operating temperature range, which is insufficient to meet the wide-temperature requirements of electric vehicle power batteries. Herein, a novel electrolyte featuring an anion-enriched solvation structure is developed by incorporating ethyl difluoroacetate (DFAE), a fluorinated solvent with wide liquid range and weak solvation capability, which enables the stable operation of lithium metal batteries (LMBs) over a broad temperature range (–50 °C to 60 °C). The anion-enrich solvation structure facilitates rapid desolvation and enables the formation of inorganic-dominated interphases on both the cathode and anode surfaces. NMC811||DEF||Li cells exhibit a high specific capacity of 194.7 mAh·g^–1 at a 2 C rate and room temperature, retaining 77.16% capacity after 400 cycles. The pouch cell using DEF electrolyte successfully powered an LED panel at –50 °C, demonstrating practical viability. This innovative strategy provides a promising pathway for the development of next generation wide-temperature LMBs.

Thermally activated delayed fluorescence (TADF) materials that simultaneously exhibit short-range (SR) and long-range (LR) charge-transfer (CT) excited states represent a promising new class of emitters for organic light-emitting diodes (OLEDs). Such systems combine the advantages of conventional donor–acceptor (D–A) and multi-resonance (MR) emitters, including high photoluminescence quantum yield (PLQY), fast radiative decay (k_r) and reverse intersystem crossing rates (k_RISC), and narrowband emission profiles. However, their molecular design principles and structure–property relationships remain largely unexplored. In this work, two new TADF emitters featuring both SR-CT and LR-CT excited states were developed by attaching electron donors to an MR fragment via a boron–meta–donor linkage. Together with reference compounds, these emitters enable a systematic investigation of the influence of the donor structure and linkage mode on the key photophysical properties of such light-emitting materials. Compared with conventional boron–para–donor linked emitters, the boron–meta–donor linked designs display highly hybridized SR–LR–CT character, manifested in distinctive emission bandwidths, enhanced solvatochromism, and donor-strength-dependent excited-state kinetics. Leveraging these features, high-performance narrowband OLEDs were fabricated, achieving a maximum external quantum efficiency (EQE_max) of 35.1% and exhibiting remarkably low efficiency roll-off, with an EQE of 18.1% maintained at a luminance of 10,000 cd·m⁻².

α-Nitroketones represent an important class of organic compounds in synthetic chemistry because of the synergistic interaction between their adjacent carbonyl and nitro functional groups. However, current reporting methods often pose environmental concerns and require harsh reaction conditions, such as the use of noble metal catalysts and external oxidants. Herein, we report a novel and environmentally benign electrochemical bifunctional groups strategy for the efficient synthesis of α-nitroketones directly from olefins. This approach is based on a dual-source system, in which Fe(NO₃)₃·9H₂O serves as a versatile precursor, simultaneously supplying the nitro group, while trace amounts of water inherently present in the electrolyte act as the oxygen source for carbonyl formation. This tandem oxidation–nitration process enables the direct construction of the valuable α-nitroketone scaffold from simple starting materials in a single operational step. A primary advantage of this methodology lies in its inherently green and sustainable nature. Compared with conventional methods, this strategy markedly decreases the necessity of using hazardous and volatile nitromethane as a nitro source and avoids the routine application of stoichiometric condensation or oxidizing agents that tend to produce large quantities of chemical waste. Instead, electricity functions as a traceless redox agent, driving the transformation under mild conditions—generally at room temperature or with minimal heating and under ambient pressure. This leads to a significantly reduced environmental footprint and enhances operational safety. The reaction demonstrates remarkable synthetic utility, characterized by a broad substrate scope. A wide variety of olefins, including those bearing aryl, aliphatic, and heterocyclic substituents, are smoothly converted into the corresponding α-nitroketones in moderate to good yields. In summary, we have developed a mild, efficient, and sustainable electrochemical route to α-nitroketones. By integrating atom-economic principles with the advantages of electrosynthesis—including inherent safety and scalability—this work provides a powerful and practical alternative to conventional methods, aligning with the growing demands of modern green chemistry.