Latest ArticlesThe transition metal-catalyzed C-H activation have been considered as increasingly useful approach for installing new functional groups onto organic small molecules due to their high step- and atom-economy, the abundance of hydrocarbon compounds, and the potential for late-stage functionalization of complex organic molecules. The ortho- and meta-C-H activation and functionalization of aromatic compounds have been widely explored in recent years, however the distal para-C-H activation and functionalization has remained a significant challenge because of the difficulty in forming energetically favorable metallacyclic transition states. The utilization of appropriate directing groups or templates as well as the meticulous design of catalysts and ligands has proven to be effective in transition-metal-catalyzed remote para-C-H bonds activation and functionalization of aromatic compounds. This review aims to summarize the strategies for controlling para-selective C-H functionalization using the directing group, template engineering, and catalyst/ligand design under transition metals catalysis in recent years.
Room-temperature phosphorescence (RTP) materials exhibiting long emission lifetimes have gained increasing attention owing to their potential applications in encryption, anti-counterfeiting, and sensing. However, most polymers exhibit a short RTP lifetime (<1 s) because of their unstable triplet excitons. Herein, a new strategy of polymer chain stabilized phosphorescence (PCSP), which yields a new kind of RTP polymers with an ultralong lifetime and a sensitive oxygen response, has been reported. The rigid polymer chains of poly(methyl mathacrylate) (PMMA) immobilize the emitter molecules through multiple interactions between them, giving rise to efficient RTP. Meanwhile, the loosely-packed amorphous polymer chains allow oxygen to diffuse inside, endowing the doped polymers with oxygen sensitivity. Flexible and transparent polymer films exhibited an impressive ultralong RTP lifetime of 2.57 s at room temperature in vacuum, which was among the best performance of PMMA. Intriguingly, their RTP was rapidly quenched in the presence of oxygen. Furthermore, RTP microparticles with a diameter of 1.63 µm were synthesized using in situ dispersion polymerization technique. Finally, oxygen sensors for quick, visual, and quantitative oxygen detection were developed based on the RTP microparticles through phosphorescence lifetime and image analysis. With distinctive advantages such as an ultralong lifetime, oxygen sensitivity, ease of fabrication, and cost-effectiveness, PCSP opens a new avenue to sensitive materials for oxygen detection.
Triphenylamine (TPA) is the most promising donor fragment for the construction of long-wavelength thermally activated delayed fluorescence (TADF) emitters owing to its suitable dihedral angle that could enhance radiative decay to compete with the serious non-radiative decay. However, the moderate electron-donating capacity of TPA seriously limits the selection of acceptor for constructing long-wavelength TADF emitters with narrow bandgaps. To address this issue, in this work, the peripheral benzene of TPA was replaced with 1,4-benzodioxane and anisole to obtain two new electron-donating units N-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-N-phenyl-2,3-dihydrobenzo[b][1,4]dioxin-6-amine (TPADBO, −5.02 eV) and 4-methoxy-N-(4-methoxyphenyl)-N-phenylaniline (TPAMO, −5.00 eV), which possess much shallower highest occupied molecule orbital (HOMO) energy levels than the prototype TPA (−5.33 eV). Based on TPA and the modified TPA donor fragments, three TADF emitters were designed and synthesized, namely Py-TPA, Py-TPADBO and Py-TPAMO, with the same acceptor fragment 12-(2,6-diisopropylphenyl)pyrido[2′,3′:5,6]pyrazino[2,3-f][1,10]phenanthroline (Py). Among them, Py-TPAMO exhibits the highest photoluminescence quantum yield of 78.4% and the smallest singlet-triplet energy gap, which is because the introduction of anisole does not cause significant molecule deformation for the excited Py-TPAMO. And Py-TPAMO-based OLEDs successfully realize a maximum external quantum efficiency of 25.5% with the emission peak at 605 nm. This work provides a series of candidate of donor fragments for the development of efficient long-wavelength TADF emitters.
Metal ions trigger Fenton/Fenton-like reactions, generating highly toxic hydroxyl radicals (•OH) for chemodynamic therapy (CDT), which is crucial in inducing lethal oxidative DNA damage and subsequent cell apoptosis. However, tumor cells can counteract this damage through repair pathways, particularly MutT homolog 1 (MTH1) protein attenuation of oxidative DNA damage. Suppression of MTH1 can enhance CDT efficacy, therefore, orderly integrating Fenton/Fenton-like agents with an MTH1 inhibitor is expected to significantly augment CDT effectiveness. Carrier-free CuTH@CD, self-assembled through the supramolecular orchestration of γ-cyclodextrin (γ-CD) with Cu2+ and the MTH1 inhibitor TH588, effectively overcoming tumor resistance by greatly amplifying oxidative damage capability. Without additional carriers and mediated by multiple supramolecular regulatory effects, CuTH@CD enables high drug loading content, stability, and uniform size distribution. Upon internalization by tumor cells, CuTH@CD invalidates repair pathways through Cu2+-mediated glutathione (GSH) depletion and TH588-mediated MTH1 inhibition. Meanwhile, both generated Cu+ ions and existing ones within the nanoassembly initiate a Fenton-like reaction, leading to the accumulation of •OH. This strategy enhances CDT efficiency with minimal side effects, improving oxidative damage potency and advancing self-delivery nanoplatforms for developing effective chemodynamic tumor therapies.
Transition metal cobalt exhibits strong activation capabilities for alkanes, however, the instability of Co sites leads to sintering and coke deposition, resulting in rapid deactivation. Hierarchical zeolites, with their diverse pore structures and high surface areas, are used to effectively anchor metals and enhance coke tolerance. Herein, a post-treatment method using an alkaline solution was employed to synthesize meso-microporous zeolite supports, which were subsequently loaded with Co species for propane dehydrogenation catalyst. The results indicate that the application of NaOH, an inorganic base, produces supports with a larger mesopore volume and more abundant hydroxyl nests compared to TPAOH, an organic base. UV–vis, Raman, and XPS analyses reveal that Co in the 0.5Co/SN-1–0.05 catalyst is mainly in the form of tetrahedral Co2+, which effectively activates CH bonds. In contrast, the 0.5Co/S-1 catalyst contains mainly Co3O4 species. Co2+ supported on hierarchical zeolites shows better propane conversion (58.6%) and propylene selectivity (>96%) compared to pure silica zeolites. Coke characterization indicates that hierarchical zeolites accumulate more coke, but it is mostly in the form of easily removable disordered carbon. The mesopores in the microporous zeolite support help disperse the active Co metal and facilitate coke removal during dehydrogenation, effectively preventing deactivation from sintering and coke coverage.
Photocatalytic overall water splitting is a promising method for producing clean hydrogen energy, but faces challenges such as low light utilization efficiency and high charge carrier recombination rates. This study demonstrates that dielectric Mie resonance in TiO2 hollow nanoshells can enhance electric field intensity and increase light absorption through resonant energy transfer, compared to crushed TiO2 nanoparticles. The Mie resonance effect was confirmed through fluorescence spectra, photo-response current measurements, photocatalytic water splitting experiments, and Mie calculation. The incident electric-field amplitude was doubled in hollow nanoshells, allowing for increased light trapping. Additionally, the spatially separated Pt and RuO2 cocatalysts on the inner and outer surfaces facilitated the separation of photoinduced electrons and holes. Pt@TiO2@RuO2 hollow nanoshells exhibited superior photocatalytic water splitting performance, with a stable H2 generation rate of 50.1 µmol g−1 h−1 and O2 evolution rate of 25.1 µmol g−1 h−1, outperforming other nanostructures such as TiO2, Pt@TiO2, and TiO2@RuO2 hollow nanoshells. This study suggests that dielectric Mie resonance and spatially-separated cocatalysts offer a new approach to simultaneously enhance light absorption and charge carrier transfer in photocatalysis.
Simultaneous degradation and detoxification during pharmaceutical and personal care product removal are important for water treatment. In this study, sodium niobate nanocubes decorated with graphitic carbon nitride (NbNC/g-C3N4) were fabricated to achieve the efficient photocatalytic degradation and detoxification of ciprofloxacin (CIP) under simulated solar light. NaNbO3 nanocubes were in-situ transformed from Na2Nb2O6·H2O via thermal dehydration at the interface of g-C3N4. The optimized NbNC/g-C3N4–1 was a type-Ⅰ heterojunction, which showed a high conduction band (CB) level of −1.68 eV, leading to the efficient transfer of photogenerated electrons to O2 to produce primary reactive species, •O2−. Density functional theory (DFT) calculations of the density of states indicated that C 2p and Nb 3d contributed to the CB, and 0.37 e– transferred from NaNbO3 to g-C3N4 in NbNC/g-C3N4 based on the Mulliken population analysis of the built-in electric field intensity. NbNC/g-C3N4–1 had 3.3- and 2.3-fold of CIP degradation rate constants (k1 = 0.173 min−1) compared with those of pristine g-C3N4 and NaNbO3, respectively. In addition, N24, N19, and C5 in CIP with a high Fukui index were reactive sites for electrophilic attack by •O2−, resulting in the defluorination and ring-opening of the piperazine moiety of the dominant degradation pathways. Intermediate/product identification, integrated with computational toxicity evaluation, further indicated a substantial detoxification effect during CIP degradation in the photocatalysis system.
The addition of cold flow improvers (CFIs) is considered as the optimum strategy to improve the cold flow properties (CFPs) of diesel fuels, but this strategy is always limited by the required large dosage. To obtain low-dosage and high-efficiency CFIs for diesel, 1,2,3,6-tetrahydrophthalic anhydride (THPA) was introduced as a third and polar monomer to enhance the depressive effects of alkyl methacrylate-trans anethole copolymers (C14MC-TA). The terpolymers of alkyl methacrylate-trans anethole-1,2,3,6-tetrahydrophthalic anhydride (C14MC-TA-THPA) were synthesized and compared with the binary copolymers of C14MC-TA and alkyl methacrylate-1,2,3,6-tetrahydrophthalic anhydride (C14MC-THPA). Results showed that C14MC -THPA achieved the best depressive effects on the cold filter plugging point (CFPP) and solid point (SP) by 11 ℃ and 16 ℃ at a dosage of 1250 mg/L and monomer ratio of 6:1, while 1500 mg/L C14MC-TA (1:1) reached the optimal depressive effects on the CFPP and SP by 12 ℃ and 18 ℃. THPA introduction significantly improved the depressive effects of C14MC-TA. Lower dosages of C14MC-TA-THPA in diesel exerted better improvement effects on the CFPP and SP than that of C14MC-TA and C14MC-THPA. When the monomer ratio and dosage were 6:0.6:0.4 and 1000 mg/L, the improvement effect of C14MC-TA-THPA on diesel reached the optimum level, and the CFPP and SP were reduced by 13 ℃ and 19 ℃, respectively. A 3D nonlinear surface diagram fitted by a mathematical model was also used for the first time to better understand the relationships of monomer ratios, dosages, and depressive effects of CFIs in diesel. Surface analysis results showed that C14MC-TA-THPA achieved the optimum depressive effects at a monomer ratio of 6:0.66:0.34 and dosage of 1000 mg/L, and the CFPP and SP decreased by 14 ℃ and 19 ℃, respectively. The predicted results were consistent with the actual ones. Additionally, the improvement mechanism of these copolymers in diesel was also explored.
The development of general and practical strategies toward the construction of medium-sized rings is still challenging in organic synthesis, especially for the multiple stereocenters control of substituted groups on the ring owing to the long distance between groups. Thus, stereoselective synthesis of multi-substituted ten-membered rings is attractive. Herein, a rapid assembly of various highly substituted ten-membered nitrogen heterocycles between two 1,3-dipoles through a tandem [3 + 3] cycloaddition/aza-Claisen rearrangement of N-vinyl-α,β-unsaturated nitrones and aza-oxyallyl or oxyallyl cations are disclosed. Products containing two or multiple stereocenters could be obtained in up to 96% yield with high regioselectivity and diastereoselectivity. Selective N-O bond cleavages of ten-membered nitrogen heterocycles lead to various novel 5,6,6-perifused benzofurans, bicyclo[4.4.0] or bicyclo[5.3.0] skeletons containing three or multiple continuous stereocenters in good yields and high diastereoselectivity. Biological tests show that the obtained ten-membered N-heterocycles and bicyclo[4.4.0] skeletons inhibited nitric oxide generation in LPS-stimulated RAW264.7 cells and might serve as good anti-inflammatory agents.
Rational tuning of crystallographic surface and metal doping were effective to enhance the catalytic performance of metal organic frameworks, but limited work has been explored for achieving modulation of crystal facets and metal doping in a single system. MIL-68(In) was promising for photocatalytic applications due to its low toxicity and excellent photoresponsivity. However, its catalytic activity was constrained by severe carrier recombination and a lack of active sites. Herein, increased (001) facet ratio and active sites exposure were simultaneously realized by cobalt doping in MIL-68(In) through a one-pot solvothermal strategy. Optimized MIL-68(In/Co)-2.5 exhibited remarkable catalytic performance in comparison with pristine MIL-68(In) and other MIL-68(In/Co). The reaction kinetic constant and degradation efficiency of MIL-68(In/Co) were approximately twice and 17% higher than the pristine MIL-68(In) in 36 min reaction, respectively. Density functional theory calculations revealed that Co dopant could modulate the orientation of MIL-68(In) facets, facilitate the exchange of electrons and reduce the adsorption energy of peroxymonosulfate (PMS). This work provides a novel pathway for improvement of In-based MOFs in PMS/vis system, it also promotes the profound comprehension of the correlation between crystal facet regulation and catalytic activation in the PMS/vis system.
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