Science China Chemistry最新文献

The synthesis of mesoporous zeolite-anchored atomically dispersed metal catalysts (ADCs) is a considerable challenge in chemistry and materials science. Here we report the synthesis of atomically dispersed cationic nickel-confined mesoporous ZSM-48 (ANMZ-48) by in situ hydrothermal reaction employing a designed tri-functional metal complex template, by which the triquaternary ammonium groups in the hydrophilic region direct the formation of ZSM-48 zeolite; the aromatic groups in the hydrophobic tail generate the mesopores through π-π stacking; and the complexes formed by nickel ions coordinated with terpyridyl groups generate atomically dispersed Ni²⁺ confined in zeolite frameworks due to the strong sintering resistance generated by the strong coordination interaction. The ANMZ-48 is consisting of stacking of sheet-like ZSM-48 domains connected by multiply crystal twinning sharing the common (011) plane, generating abundant of imbedded mesopores with the uniform thickness of ∼2.4 nm and with the width of 10–50 nm. The excellent catalytic activity and stability of ANMZ-48 were also reflected in the dry reforming of methane (DRM) reaction.

Versatile stimuli-responsive circularly polarized luminescent (CPL) materials have potential applications in information storage, security encryption, and intelligent displays. In this study, the Z/E isomerization of ultraviolet (UV)-photosensitive achiral α-cyanostilbene derivative was used as an achiral dichroic dye (Switch) to drive the controllable CPL-active response in cholesteric liquid crystals (CLCs). Under irradiation by 365 nm UV light, the resulting CLCs-Z-Switch underwent a Z-to-E configuration isomerization as CLCs-E-Switch, accompanied by a decrease in its dichroic order parameter (S_F value) from 0.15 to 0.07. Although the quantum yield (QY) of CLCs-E-Switch increased from 8.1% (CLCs-Z-Switch) to 16.8%, the corresponding g_lum values of CPL emission decreased from +0.55/−0.57 to +0.37/−0.39 due to a decrease in the order of helical arrangement of E-Switch in E7 media. This study enables photosensitive CLCs-Switch to be applied for optical information storage devices.

Tumor hypoxia severely limits the therapeutic efficacy of photodynamic therapy (PDT) for solid tumors, which is highly dependent on tissue oxygen concentration. In this study, we developed a platinum(II)-acetylide-based metallacycle compound bearing six 1,4-dimethylnaphthalenes (DMN) groups, and controlled the photodynamic and photothermal effects of the compound by adjusting the power of 730 nm laser to achieve reversible sensitization, storage and release of ¹O₂ within a single molecule. The compound formed nanoparticles by self-assembly and exhibited good water solubility and biocompatibility. Under laser irradiation, the strong spin-orbit coupling of platinum atoms in the metallacycle facilitated ¹O₂ generation. The produced ¹O₂ was captured by the DMN carriers and transported into the hypoxic tumor, where ¹O₂ release was triggered owing to the good photothermal effect of the extended conjugation of the metallacycle. During therapy, the metallacycle serving as a photosensitizer, ¹O₂ carrier, and photothermal reagent, achieved the synergistic therapy of PDT/PTT, demonstrating the versatility of the metallacycle. This study proposes a new strategy to develop phototherapy agents that are suitable for hypoxic tumors.

An asymmetric catalytic strategy in photocatalysis utilizing a chirality-induced approach through an organocatalytic/photoredox relay catalysis strategy is successfully achieved for the rapid construction of polycyclic compounds containing vicinal amino alcohols in a one-pot protocol. This methodology facilitates the efficient synthesis of diverse substituted polycyclic tetra-hydroquinoline and benzofuran-derived vicinal amino alcohols, each containing five consecutive chiral centers, with high yields, excellent diastereoselectivities and enantioselectivities (up to 95% yield, >20:1 dr and 98% ee), under mild reaction conditions driven by sequential bifunctional squaramide organocatalyst-catalyzed [4+2] annulation and photocatalyst-catalyzed ketyl radical addition cyclization reaction process. Furthermore, investigations into the stereoselectivity mechanism and high-resolution mass spectrometry (HRMS) experiments on free radical trapping have provided evidence for elucidating the detailed mechanism of chirality-induced processes and chiral intermediate conversions in this procedure.

Molecular solid solutions of metal clusters containing different metal centers with well-defined structures can accurately regulate the HOMO-LUMO gap, but are rarely available. Herein, a series of colorless lanthanide-titanium-oxo clusters Ln₂Ti₄(μ₂-O)₂(μ₃-O)₄(Piv)₁₀(THF)₂ (Ln₂Ti₄, Ln = Eu, Gd, Tb, and Ce, HPiv = pivalic acid) were synthesized by the reaction of pivalic acid with Ln(Ac)₃ and titanium isopropoxide. The light yellow crystal of cluster solid solutions Eu₂Ti_4−xCd_x, containing a mixture of Eu₂Ti₄ and Eu₂Ti₃Cd, was obtained by in situ doping Cd²⁺ and S²⁻. Eu₂Ti_3.92Cd_0.08 displays efficient photocatalytic hydrogen evolution activity without a co-catalyst, which is up to 2.6 times that of Eu₂Ti₄. Femtosecond time-resolved transient absorption spectroscopy and spin-polarized density functional calculations showed that the enhanced photocatalytic performance of Eu₂Ti_4−xCd_x can be attributed to the narrower HOMO-LUMO gap and lower LUMO position than that of Eu₂Ti₄. This studyprovides an in situ doping method to realize the simple preparation of cluster solid solution.

Transition metal-catalyzed olefination of aryl C–H bond is a powerful tool for the synthesis of alkenes. While the Pd-catalyzed oxidative C–H olefination of arenes, also known as Fujiwara-Moritani reaction, has been established as one of the most efficient methods, the substrates are largely limited to terminal olefins with electron-withdrawing group(s). Herein, we report a synergistic silver-mediated and palladium-catalyzed non-directed C–H olefination of arenes with vinyl (pseudo)halides, which offers a complementary strategy to the typical Fujiwara-Moritani reaction. The reactions proceeded well for a variety of halogenated arenes, heteroarenes, and olefin substrates, providing an efficient access to various multi-substituted aryl olefins, including trisubstituted/tetrasubstituted olefins and several complex olefins derived from medicines or natural products. Mechanistic studies indicated a bimetallic Pd/Ag cooperation is operative in the catalysis, i.e., the reaction is initiated by aryl C–H bond cleavage via ligation with phosphine/Ag species, followed by transferring of the aryl moiety to a vinyl palladium intermediate, which is in turn formed by oxidative addition of vinyl (pseudo)halide to a Pd complex. This method enables the synthesis of a wide range of challenging multi-substituted vinyl products from simple arenes (directing-group free) in a streamlined and controllable fashion.

Carbon dioxide reduction, as a sustainable and versatile strategy for the access of chemical fuels, has attracted increasing attention and enormous efforts have been devoted to it in recent years. However, employing carbon dioxide as double synthons via bimolecular reduction remains challenging. Here, by leveraging the bimolecular reduction of carbon dioxide to carbonyl and methyl respectively, we describe a Pd-catalyzed trifunctionalization of alkynes with aryl iodide for the first time and showcase its advantages on the formation of various β-diketones and their application in the constructing of heterocyclic compounds with important biological activity, including pyrimidine, oxazole, pyrazole