Science China Chemistry最新文献

Asymmetric reductive amination directly converts ketones and amines to alkylamines, which are important motifs in medicines. We report that cationic nickel complexes of chiral diphosphines promote enantioselective reductive amination of benzylic ketones with both arylamines and benzhydrazide. Isopropanol was used as a safe and cheap source of hydrogen instead of formic acid. The reaction can be readily applied to a concise synthesis of diarylethylamines, a class of neuroactive substances.

The effect of side-chain engineering of conjugated molecules on the morphology and device performance in binary organic solar cells has been widely investigated. However, this relationship has hardly been studied in the guest components of ternary organic solar cells. In this study, a family of non-fullerene guest acceptors, namely XY-3, XY-5 and XY-7, with hydrogen substituent, straight and branched alkyl chains on the bithiophene units, respectively, were designed and synthesized to understand their effects on aggregation properties and device performance. The straight and branched alkyl chains on the bithiophene units result in sightly blue-shifted absorption compared to the hydrogen substituent and the XY-7 demonstrates the most appropriate phase separation scale and the most balanced charge transport. Consequently, the OSCs based on D18:eC9:XY-7 achieve a high short-circuit current density (J_SC) and fill factor (FF), while maintaining the enhancement of the open-circuit voltage (V_OC) achieving an efficiency of 19.32%, exceeding those of D18:eC9, D18:eC9:XY-3, D18:eC9:XY-5 (PCE:18.28%, 19.04%, 18.75%, respectively). These results highlight that the side-chain engineering of Y series non-fullerene acceptors as the guest acceptors has great potential in optimizing morphology properties and promoting photovoltaic performance.

Luminescent organic radicals have garnered increasing attention owing to their versatile applications in sensing, imaging, and organic light-emitting diodes (OLEDs), attributed to their unique emission properties originating from the doublet spin state. However, the natural narrow bandgap of organic free radicals typically limits their emission to the long-wavelength region. Designing luminescent organic radicals with short-wavelength emission remains a significant challenge. Herein, a series of carbon-centered radicals with short-wavelength emission (383–476 nm) by combining N-heterocyclic carbenes with various polycyclic aromatic hydrocarbons (PAHs) (2-naphthyl, 2a^I and 2b^I; 2-phenanthryl, 2a^II and 2b^II; 2-anthryl, 2a^III and 2b^III; 3-phenanthryl, 2a^IV and 2b^IV). Theoretical calculations reveal that the introduction of PAHs significantly increases the ΔE_D2-D1 in 2a^I–III and 2b^I–III compared to that in phenyl-derived radical congeners. Consequently, the internal transition from D2 to D1 is impeded, leading to a high yield of D2 emission and a suppressed Kasha’s rule, thereby overcoming the limitations imposed by their narrow bandgap. For 2a^IV and 2b^IV, despite a moderately large ΔE_D2-D1 value, the ΔE_D3-D1 value exceeds 1 eV, indicating that their emission likely originates from the D3 state. Furthermore, we utilized 2a^III and 2b^III as emissive materials in OLEDs, resulting in blue emissions with external quantum efficiencies of 7.5% and 6.5%, respectively.

Recent years have witnessed the transformative impact from the integration of artificial intelligence with organic and polymer synthesis. This synergy offers innovative and intelligent solutions to a range of classic problems in synthetic chemistry. These exciting advancements include the prediction of molecular property, multi-step retrosynthetic pathway planning, elucidation of the structure-performance relationship of single-step transformation, establishment of the quantitative linkage between polymer structures and their functions, design and optimization of polymerization process, prediction of the structure and sequence of biological macromolecules, as well as automated and intelligent synthesis platforms. Chemists can now explore synthetic chemistry with unprecedented precision and efficiency, creating novel reactions, catalysts, and polymer materials under the data-driven paradigm. Despite these thrilling developments, the field of artificial intelligence (AI) synthetic chemistry is still in its infancy, facing challenges and limitations in terms of data openness, model interpretability, as well as software and hardware support. This review aims to provide an overview of the current progress, key challenges, and future development suggestions in the interdisciplinary field between AI and synthetic chemistry. It is hoped that this overview will offer readers a comprehensive understanding of this emerging field, inspiring and promoting further scientific research and development.

Exploration of single molecular species synchronously featured by long excitation/emission wavelength, accurate diagnosis, and effective therapy, remains supremely appealing to implement high-performance cancer phototheranostics. However, those previously established phototheranostic agents are undiversified and stereotyped in terms of structural skeleton, and generally exhibit insufficient phototheranostic outcomes. Herein, we innovatively utilized indanone-condensed thiadiazolo[3,4-g]quinoxaline (ITQ) as electron acceptor to construct novel photosensitizer with second near-infrared (NIR-II) emission. Experimental study and theoretical calculation demonstrated that comparing with the counterparts constituting by widely employed NIR-II building block benzobisthiadiazole (BBTD) and 6,7-diphenylthiadiazoloquinoxaline (DPTQ), ITQ-based photosensitizer (TITQ) showed superior aggregation-induced emission (AIE) characteristics, much stronger type-I reactive oxygen species (ROS) production, and prominent photothermal conversion capacity. Furthermore, TITQ nanoparticles with excellent biocompatibility were capable of effectively accumulating in the tumor site and visualizing tumor through fluorescence-photoacoustic-photothermal trimodal imaging with highly spatiotemporal resolution, and completely eliminating tumor by type-I photodynamic-photothermal therapy.

Organocatalytic cascade reactions represent a powerful strategy for the rapid construction of complex chiral molecules with multiple stereocenters from simple substrates under mild conditions. The intriguing structural feature and diverse reactivity of catalytically generated dienolate species render them competent and versatile intermediates for the development of practical and valuable cascade reactions. Over the past years, a plethora of innovative and pioneering noncovalent ammonium dienolate-mediated cascade reactions have been designed and implemented under the catalysis of chiral organocatalysts, making dienolate activation a general, robust, and complementary method for the functionalization of unsaturated carbonyl compounds and related substances. This review illustrates the recent advances in organocatalytic noncovalent ammonium dienolate-mediated cascade reactions (mainly from 2010 to 2023), including the cascade transformations of ammonium dienolates directly generated from unsaturated ketone/aldehyde, ester/lactone/azlactone, amide/lactam/pyrazolone/oxindole, and alkylidene nitrile compounds. The contents are arranged based on the reaction types of the ammonium dienolates, with an emphasis on cascade 2,5-, 3,5-, and 4,5-difunctionalizations of these intermediates. Furthermore, other cascade reactions involving the 1,3-, 2,3-, and even more complex 3,4,5-reactivities of ammonium dienolates were also discussed. The reaction pathway, reaction stereoinduction, and synthetic applications of the ammonium dienolate-mediated cascade reactions were highlighted throughout the article. As a stimulating and ever-growing research area, the organocatalytic noncovalent ammonium dienolate-mediated cascade reactions are expected to continue demonstrating their magic power for constructing chiral targets in the future and further expanding the boundaries of asymmetric catalysis.

The development of efficient Si–O bond formation reaction with 100% atom-economy, excellent functional group tolerance, and broad scope under mild conditions is highly desired due to the prevalence of silanol, silyl ether, and their derivatives in synthetic chemistry and materials science. Here, we have realized the Pd-catalyzed Si–O formation reaction via a Si–C activation approach with 100% atom-economy by employing silacyclobutanes (SCBs) and various hydroxy-containing substrates, including water, alcohols, phenols, and silanols. This protocol features a broad substrate scope, remarkable functional compatibility and mild conditions, providing a series of silanols, silyl ethers in high efficiency. Notably, this protocol could also be used for selective protection of hydroxy functionalities, and for the access of a class of novel polymers containing Si–O main chain. Preliminary mechanistic studies unveiled that this reaction underwent a Pd-catalyzed concerted ring-opening mechanism.

Developing highly sensitive optical thermometers is of great significance due to their capability to enable remote and non-contact temperature measurements, rendering them highly applicable in diverse and harsh environments. Herein we report a temperature-dependent phosphor of 0D metal halide hybrid by incorporating Bi³⁺ into the (MePPh₃)₂ZnCl₄ matrix. Through Bi³⁺ doping, the initially non-luminescent (MePPh₃)₂ZnCl₄ matrix exhibits a deep-blue emission centered at 453 nm, with a photoluminescence quantum yield (PLQY) of 5.71% and a Stokes shift of 75 nm at room temperature. Experimental characterization demonstrates that exciton-like luminescence of Bi³⁺ is mainly responsible for the blue emission. Single crystals of Bi³⁺-doped (MePPh₃)₂ZnCl₄ show an unusual correlation between photoluminescence (PL) lifetime and temperature. Particularly, the dependence of luminescence lifetime on temperature is most remarkable in the temperature range of 80 to 100 K with an exceptional sensitivity up to 0.09 K⁻¹, representing one of the best levels for thermometry based on PL decay lifetime. Our work not only provides a viable strategy for designing a novel, environmentally friendly, and stable blue emitter, but also paves the way for precise thermometric application at low temperature.

Seawater electrolysis is an effective way to obtain hydrogen (H₂) in a sustainable manner. However, the lack of electrocatalysts with high activity, stability, and selectivity for oxygen evolution reaction (OER) severely hinders the development of seawater electrolysis technology. Herein, sulfur-doped nickel-iron selenide nanosheets (S-NiFeSe₂) were prepared by an ion-exchange strategy and served as highly active OER electrocatalyst for alkaline seawater electrolysis. The overpotential is 367 mV, and it can run stably for over 50 h at 100 mA cm⁻². Excitingly, the S-NiFeSe₂∥Pt/C pair exhibits cell voltage of 1.54 V at 10 mA cm⁻² under alkaline seawater conditions, which can run smoothly for 100 h without decay, and the efficiency of electricity-to-hydrogen (ETH) energy conversion reaches more than 80%. Such electrode, with abundant accessible reactive sites and good corrosion resistance, is a good candidate for seawater electrolysis. Moreover, density functional theory calculations reveal that the surface sulfur atoms can activate the adjacent Ni sites and decrease the free energy changes of the associated intermediates at the adjacent Ni sites for OER, and the step of *OH → *O is the potential rate-limiting step. In this work, the true reactive site in nickel-iron selenides is the Ni sites, but not the Fe sites as commonly believed.

CF₂H-containing molecules play pivotal roles in diverse fields from medicinal chemistry to materials science. However, the application of existing CF₂H reagents as a source of CF₂H radical is limited by their reactivity and preparation. Herein, we develop a simple and general visible-light-catalyzed radical difluoromethylation reaction of alkenes, dienes, and heteroaromatics using commercially available, easy-to-handle, and low-cost difluoroacetic anhydride as the CF₂H reagent. This scalable protocol enables the convenient synthesis of a range of CF₂H-containing compounds under mild conditions, exhibiting a broad substrate scope and functional group tolerance. Potential applications are further demonstrated by gram-scale synthesis, sunlight experiments, derivatization experiments as well as the synthesis of bioactive molecules.