Latest ArticlesHighly enantioselective Rh-catalyzed partial hydrogenation of unprotected simple 2-alkyl-5-aryl-disubstituted pyrroles has been successfully developed, generating a series of chiral 1-pyrroline derivatives generally with excellent results (95%–99% yields, 91%–96% ee). Moreover, 2,5-aryl-1H-pyrroles were hydrogenated well in high yields and good enantioselectivities. This efficient protocol features easily accessible substrates, wide substrate scope, well functional group compatibility, commercially available rhodium precursor and chiral ligand. It provides a versatile route to access chiral 1-pyrroline derivatives that are of great importance in organic synthesis and pharmaceutical chemistry.
The need for temporal resolution and long-term stability in super-resolution fluorescence imaging has motivated research to improve the photostability of fluorescent probes. Due to the inevitable photobleaching of fluorophores, it is difficult to obtain long-term super-resolution imaging regardless of the self-healing strategy of introducing peroxide scavengers or the strategy of fluorophore structure modification to suppress TICT formation. The buffered fluorogenic probe uses the intact probes in the buffer pool to continuously replace the photobleached ones in the target, which greatly improves the photostability and enables stable dynamic super-resolution imaging for a long time. But the buffering capacity comes at the expense of reducing the number of fluorescent probes in targets, resulting in low staining fluorescence intensity. In this paper, we selected BODIPY 493, a lipid droplet probe with high fluorescence brightness, to explore the dynamic process of lipid droplet staining of this probe in cells. We found that BODIPY 493 only needs very low laser power for lipid droplet imaging due to the high molecular accumulation in lipid droplets and the high brightness, and the spatiotemporal resolution is greatly improved. More importantly, we found that BODIPY 493 also has a certain buffering capacity, which enables BODIPY 493 to be used for super-resolution imaging of lipid droplet dynamics. This work reminds researchers to coordinate the buffering capacity and brightness of fluorogenic probes.
The construction of secondary alkylsilanes is a challenging subject in the synthetic community. The cross-coupling provides a practical solution to address this problem, but it typically relies on organometallic species. Herein, we report an Mn-mediated reductive C(sp3)–Si coupling to synthesize these compounds from alkyl and silyl electrophiles. This approach avoids the requirement for activation of Si–Cl by transition metals and thus allows for the coupling of various common chlorosilanes. The reaction proceeds under mild conditions and shows good functional group compatibility. The method offers access to α-silylated organophosphorus and sulfones with a scope that is complementary to those obtained from the established methods.
Recently, exploiting a novel supramolecular fabrication pathway have drawn great attention. To this endeavor, we firstly designed and reported an original light-activated platform based on the internal-driven forces of macrocyclic host by hiring the pillar[5]arene as the host molecule (H) and phenazine derivatives acting as an energetic guest molecule (G). Surprisingly, after adding the H solution into G system, the intensive fluorescence emission of the G molecule rapidly decreased under the irradiation of the UV-light (254 nm) until absolutely quenching. Delightfully, different from the traditional supramolecular host-guest interaction, the fluorescent emission of G molecule could be recovered after irradiating under the nature light. In view of this interesting observations, the interaction mechanism was carefully investigated by a series of characterizations. Those results suggested that the G molecule was easily threaded into the macrocyclic cavity (H) under the internal-driven forces induced by the UV-light irradiation, forming a 1:1 host-guest complex. Moreover, taking advantage of this especial feature, the light-activated platform of host–guest complex was further applied for ink-free light-driven printing materials, exhibiting great potential in the real application.
Ammonia is one of the most essential chemicals in the modern society but its production still heavily relies on energy-consuming Haber-Bosch processes. The photocatalytic reduction of nitrogen with water for ammonia production has attracted much attention recently due to its synthesis under mild conditions at room temperature and atmospheric pressure using sunlight. Herein, we report a high-performance Au/MIL-100(Cr) photocatalyst, comprising MIL-100(Cr) and Au nanoparticles in photocatalytic nitrogen reduction to ammonia at ambient conditions under visible light irradiation. The optimized photocatalyst (i.e., 0.10Au/MIL-100(Cr)) achieved the excellent ammonia production rate with 39.9 µg gcat−1 h−1 compared with pure MIL-100(Cr) (2.73 µg gcat−1 h−1), which was nearly 15 times that on pure MIL-100(Cr). The remarkable activity could be attributed to the adsorption-plasmonic synergistic effects in which the MIL-100(Cr) and Au are responsible to the strong trapping and adsorption of N2 molecules and photo-induced plasmonic hot electrons activating and decomposing the N2 molecules, respectively. This study might provide a new strategy for designing an efficient plasmonic photocatalyst to improve the photocatalytic performance of N2 fixation under visible light irradiation.
A green and highly efficient strategy for the preparation of bridged spirocyclic compounds via visible-light-induced cyclization of 2-(2-(arylethynyl)benzylidene)malononitrile derivatives with 2,6-di(tert-butyl)-4-methylphenol (BHT) at room temperature was developed. The photoinduced radical reactions generated the corresponding products in good yields under simple and mild reaction conditions.
Graphene oxide (GO) has been widely used in the modification of membranes due to its excellent properties, i.e., huge specific surface area, good electrical conductivity, good hydrophilicity and various functional groups. The addition of GO in membranes were proved to exhibit improved properties in water permeability, molecular selectivity, membrane fouling mitigation and contaminants decomposition. Recently, the development of laminated GO in membranes achieved both high selectivity and high water permeability, conquering the limitations of conventional polymeric or inorganic membranes. By analyzing the separation mechanisms and the performance of GO composite membranes, this review systematically summarized the applications of GO composite membranes in three highlighted areas of environmental fields: desalination, gas separation and wastewater treatment, with challenges discussed faced with GO composite membranes.
Once inevitably released into the aquatic environment, polystyrene nanoplastics (PS-NPs) will present complicated environmental behaviors, of which the aggregation is a key process determining their environmental fate and impact. In this study, the aggregation kinetics of different sizes (30 nm and 100 nm) of PS-NPs with metal cations (Na+, K+, Ca2+, Mg2+ and Pb2+) at different solution pH (3, 6 and 8) were investigated. The results showed that the aggregation of PS-NPs increased with cation concentration. Taking Pb2+ as an example, the adsorption behavior of cations onto PS-NPs was determined by transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) spectroscopy, which demonstrated Pb2+ could be adhered onto the surface of PS-NPs with the effect of charge neutralization. The critical coagulation concentrations (CCC) of smaller PS-NPs were higher than that of larger PS-NPs for monovalent cations, whereas a different pattern is observed for divalent cations. It was suggested that there were other factors that DLVO theory does not consider affect the stability of NPs with different particle sizes. In addition, it should be noted that PS-NPs had the capacity of adsorbing large amounts of heavy metal cations and carried them transport to a long distance, and the corresponding ecological risks need to further elucidate.
X-ray detection and imaging via scintillators has been utilized in missions worldwide within areas of scientific research, medical industry, military defense and homeland security. Commercial scintillators are costly with high energy consumption through the sintering. It is of great significance to seek alternative scintillating materials for sensitive X-ray detection in the next-generation. Herein, eight structure-defined Ln(Ⅲ)-based metal–organic frameworks (Ln-MOFs) were prepared, 2D [Ln2(1,4-ndc)3(DMF)4]n·nH2O (Ln = Sm 1, Eu 2, Dy 3, Tb 4) and 3D [Ln4(2,6-ndc)6(μ2H2O)2(H2O)4]n·2nH2O (Ln = Sm 5, Eu 6, Dy 7, Tb 8), where 1,4-H2ndc = 1,4-naphthalene dicarboxylate acid, 2,6-H2ndc = 2,6-napthalene dicarboxylate acid, DMF = N, N-dimethylformamide. Merely compounds 2 and 6 show remarkable X-ray scintillation performance via the characteristic red emissions of Eu(Ⅲ) ions, in which the absorbed energy from the triplet states of the organic moieties can be transferred more efficiently to the resonance emission levels of Eu(Ⅲ) ions than other lanthanide(Ⅲ) ions. The X-ray dosage rate detection limits of 2 and 6 are superior to the standard for the medical X-ray diagnosis dosage rate. As proofs-of-concepts, matrix-mixed membranes fabricated with 2 and 6 have achieved remarkable X-ray imaging with high resolution for practical object shooting.
An SN2-based photochemical strategy using dithiocarbamate anion as catalyst was developed for the activation of benzyl halides, which are extremely challenging to be applied as radical precursors in visible light photocatalysis. With this transition-metal-free and oxidant-free protocol, the benzylation (or cyanomethylation) of various heterocycles including quinoxalin-2(1H)-ones, coumarin, 2-phenyl-2H-indazole, 1-methyl-5-phenylpyrazin-2(1H)-one, 1-(fluoromethyl)cinnolin-4(1H)-one, and 2, 4-dibenzyl-1,2,4-triazine-3,5(2H, 4H)‑dione could be realized (46 examples, up to 98% yield). Importantly, some biologically relevant 3-benzylquinoxalin-2(1H)-ones were also be synthesized under mild conditions.
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