Chinese Chemical Letters最新文献

Two o-carborane based tetraphenylethene (TPE) cationic cyclophanes O1·4PF₆ and O2·4PF₆ were synthesized through an S_N2 reaction. Their structures were confirmed both possessing Z-shaped cavities in single crystal analysis. The optical properties of these macrocycles were systematically investigated using UV–vis spectroscopy and fluorescence techniques. It is worth noting that the introduction of a methoxy group to the TPE unit enables the synthesis of a near-infrared-emitting macrocycle O2·4PF₆. The recognition behaviors of these two macrocycles towards nucleotides were investigated using various techniques including fluorescence titration, UV–vis titration, and transmission electron microscopy (TEM). Interestingly, these cyclophanes exhibited aggregation-induced emission (AIE) effects in water or under the induction of nucleotides.

The rational design of high-performance bifunctional electrocatalysts for overall water splitting (OWS) is the key to popularize hydrogen production technology. The active metal oxyhydroxide (MOOH) formed after surface self-reconfiguration of transition metal sulfide (TMS) electrocatalyst is often regarded as the "actual catalyst" in oxygen evolution reaction (OER). Herein, an Fe doped CoS₂/MoS₂ hollow TMS polyhedron (Fe-CoS₂/MoS₂) with rich Mott-Schottky heterojunction is reported and directly utilized as an OWS electrocatalyst. The spontaneous built-in electric field (BEF) at the heterogeneous interface regulates the electronic structure and D-band center of the catalyst. More importantly, the “TMS-MOOH” core-shell structure obtained in the KOH electrolyte shows enhanced OER properties. And the introduction of Fe ions activates the inert basal plane of MoS₂, which greatly steps up the performance of HER. Hence, the preferable Fe-CoS₂/MoS₂–400 presents superior OER activity (η₁₀ = 178 mV, η₁₀₀ = 375 mV), HER activity (η₁₀ = 92 mV) and ultra-high stability for 50 h. This work has deeply explored the catalytic mechanism of TMS and provided a new idea for the construction of efficient bifunctional catalysts.

Benzo[4,5]imidazo[1,2-a]pyrimidine-based derivatives play crucial roles in medicines, pesticides, tracers and photoelectric materials. However, their synthesis approach still needs to be optimized, and their fluorescent properties in intracellular microenvironment are unclear. Here, a Cu(II)-catalyzed cascade coupling cyclization reaction was successfully developed to synthesize benzo[4,5]imidazo[1,2-a]pyrimidine scaffold with mild reaction conditions, broad substrate scopes and high yields. After a system study, we found that compound 4aa displayed an optimal viscosity-specific response with remarkable fluorescence enhancement (102-fold) for glycerol at 490 nm. Particularly, 4aa possessed excellent structure-inherent targeting (SIT) capability for lysosome (P = 0.95) with high pH stability and large Stokes shift. Importantly, 4aa was validated for its effectiveness in diagnosing lysosomal storage disorders (LSD) in living cells. The 4aa also showed its potential to map the micro-viscosity and its metabolism process in zebrafish. This work not only affords an efficient protocol to fabricate benzo[4,5]imidazo[1,2-a]pyrimidine derivatives, reveals this skeleton has excellent SIT features for lysosome, but also manifests that 4aa can serve as a practical tool to monitor lysosomal viscosity and diagnose LSD.

An efficient and scalable electrochemical asymmetric protocol with metal-free catalysts and even without additional oxidants for the cross-dehydrogenative coupling reaction (CDC) of two C(sp³)-H bonds is reported. A series of aldehydes including natural products and various substrates containing C(sp³)-H bonds including xanthenes, acridines, cycloheptatrienes and even diarylmethane have been shown to undergo asymmetric CDC to afford a series of carbon-carbon bond coupling products with up to 94% yield and 98% ee. Mechanistic studies such as radical clock experiment suggest that the reaction proceeds via nucleophilic attack by enamine under electrochemical conditions.

Surface chemistry focuses on the investigation of the adsorption, migration, assembly, activation, reaction, and desorption of atoms and molecules at surfaces. Surface chemistry plays the pivotal roles in both fundamental science and applied technology. This review will summarize the recent progresses on surface assembly, synthesis and catalysis investigated mainly by scanning tunneling microscopy and atomic force microscopy. Surface assemblies of water and small biomolecules, construction of Sierpiński triangles and surface chirality are summarized. On-surface synthesis of conjugated carbo- and heterocycles and other kinds of carbon nanostructures are surveyed. Surface model catalysis, including single-atom catalysis and electrochemical catalysis, are discussed at the single-atom level.

The first example of sono-photocatalytic bond formation was reported. With both visible light and ultrasound wave as the energy, various 3-aminoquinoxalin-2(1H)-ones were efficiently obtained with good functional group tolerance in the absence of any additive or external photocatalyst. Compared with the conventional photocatalysis, sono-photocatalysis not only dramatically improved the reaction rates and yields, but also reduced energy consumption.

Carbon-based materials with single-atom (SA) transition metals coordinated with nitrogen (M-N_x) have attracted extensive attention due to their superior electrochemical CO₂ reduction reaction (CO₂RR) performance. However, the uncontrolled recombination of metal atoms during the typical high-temperature synthesis process in M-N_x causes deterioration of CO₂RR activity. Herein, by using electrospinning, we propose a novel strategy for constructing a highly active and selective SA Fe-modified N-doped porous carbon fiber membrane catalyst (Fe-N-CF). This carbon membrane has an interconnected three-dimensional structure and a hierarchical porous structure, which can not only confine Fe to be single atom as active centers, but also provide a diffusion channel for CO₂ molecules. Relying on its special structure and stable mechanical properties, Fe-N-CF is directly used for CO₂RR, which presents an excellent selectivity (CO Faradaic efficiency of 97 %) and stability. DFT calculations reveals that the synthesized Fe-N₄-C can significantly reduce the energy barrier for intermediate COOH* formation and CO desorption. This work highlights the specific advantages of using electrospinning method to prepare the optimal SA catalysts.