Chinese Journal of Chemistry最新文献

Open-shell graphene fragments (OGFs) with non-benzenoid topologies are attracting increasing attention due to their potential applications in organic light-emitting diodes (OLEDs) and organic radical conductors. Herein, we report the synthesis of an air-stable fluorenyl radical derivative (AR1) containing a seven-membered ring, achieving thermodynamic stabilization through the fusion of a naphthalene ring around its periphery and anthracene substituent. The half-life times (τ_1/2) of AR1 in air-saturated solution is 71.9 h. The high stability was ascribed to kinetic blocking of reactive sites with high spin densities. The geometric and electronic structures of AR1 were systematically studied by combining various experimental methods and density functional theory (DFT) calculations, which include X-ray crystallographic analysis, electron spin resonance (ESR), cyclic voltammetry, and UV−vis−NIR measurements.

Imbalance in the levels of ascorbic acid (AA) can pose a risk to human health. Therefore, it's essential to establish an accurate method for the detection of AA. In this work, a novel N-doped carbon composite (MnO_x@NC) with dual enzyme-like activities to detect AA was prepared by calcination of Mn-MOF containing H₃TTPCA ligand. Interestingly, the •O₂⁻ that leads to its oxidase-like activity was not formed by dissolved oxygen, but came from the synergistic effect of lattice oxygen generated by calcination and the transformation of Mn^II/Mn^III/Mn^IV, and the presence of H₂O₂ provided much •OH, which caused its peroxidase-like activity. Meanwhile, the residual N element came from H₃TTPCA ligand assisted the catalytic process. Accordingly, a dual-signal sensing platform and smartphone-assisted recognition for detection of AA was developed and a colorimetric sensor array was established to distinguish three antioxidants. This work also demonstrates considerable promise for the detection of AA in authentic pharmaceuticals.

For coordination-insertion olefin polymerization, the development of novel transition-metal catalysts has drawn extensive attention in this field. In this contribution, we designed a series of hemilabile α-diimine nickel catalysts bearing oxygen atom as neighboring group. The steric hindrance and oxygen atom number of these nickel complexes (Ni1—Ni4) could be adjusted, which influenced ethylene (co)polymerization processes. The introduction of oxygen atoms could enhance the thermal stability during ethylene polymerization for Ni2 compared to the counterpart without oxygen atoms. And for the copolymerization process of ethylene with polar monomers, higher catalytic activity (1.4 × 10⁶ g·mol⁻¹·h⁻¹) and polar monomer incorporation ratio (1.2 mol%) were achieved. However, Ni4 with four oxygen atoms in this work was not active in ethylene polymerization due to the interaction between the oxygen atom and nickel catalytic center. The hemilabile effect in this work presented an example to enhance the stability of the α-diimine nickel catalysts in olefin polymerization.

Herein, the temperature- and pressure-stimulated responsive behavior as well as crystal-glass phase transition of a new zero-dimensional hybrid manganese bromide [4-MTPP]₂[MnBr₄] [4-MTPP⁺ = (4-methoxybenzyl)tris(phenyl)phosphonium)] were reported. Our experiment results demonstrate that [4-MTPP]₂[MnBr₄] shows typical green photoluminescence emission centered at 522.4 nm excited by UV light, with a high photoluminescence quantum yields value of 79.36% and a large lifetime of 368.6 μs, attributing to its direct bandgap electronic structure. Further, the photoluminescence emission of [4-MTPP]₂[MnBr₄] presents a monotonically blue shift with the increased temperature, originating from the decreased crystal field strength where the Mn²⁺ stays owing to lattice thermal expansion effect. On the contrary, as the pressure increases, the photoluminescence emission of [4-MTPP]₂[MnBr₄] exhibits a progressive red shift, which can be attributed to the increased crystal field strength of Mn²⁺ due to the effect of pressure-induced lattice shrinkage. Meanwhile, its quenched emission can be successfully restored when the pressure returns to the ambient pressure. In addition, [4-MTPP]₂[MnBr₄] crystals show a crystal-glass phase transition at the temperature of 74 °C. Intriguingly, the melt-quenched glass of [4-MTPP]₂[MnBr₄] exhibits green emission under UV light excitation with a large lifetime of 302.2 μs.

Herein, we report a rare example of three-component net-oxidative sulfonylation of a SO₂ surrogate with an oxidatively activated radical precursor under mild and metal- and external-oxidant-free conditions. The mildness and sustainability of the reaction are enabled by photoelectrocatalysis, and 3-aza-1,5-dienes, organotrifluoroborates and 1,4-diazabicyclo[2.2.2]octane bis(sulfur dioxide) adduct (DABSO) undergo sulfonylative cyclization to afford sulfono 4-pyrrolin-2-ones in an atom-economical manner with a broad substrate scope and good functional-group tolerance. The protocol is amenable to the late-stage diversification of complex molecular architectures as well as the gram-scale synthesis. Sunlight could be used as the light source, and the reaction could be conducted in an all-solar mode using a commercially available photovoltaic panel to generate electricity in situ. Mechanistic studies reveal that the in situ generated 1,4-diazabicyclo[2.2.2]octane (DABCO), which was generally innocent in previous reactions, functions as an electron shuttle between the photocatalytic cycle and the reactants.

Hydrazine hydrate (DH) is a widely used chemical agent, but it is highly toxic. Thus, the development of low-cost and easy-to-prepare materials for the detection and adsorption of DH is very significant. Herein, a novel and easy-to-prepare supramolecular smart material based on bisquinoline-functionalized naphthalene diimide (DQ8) has been designed and synthesized. In the DQ8, the synergistic effect between quinoline and naphthalene diimide groups has been employed to improve the selectivity and sensitivity for binding of DH. The DQ8-based crystalline porous material (DQ8-CPM) can simultaneously detect and adsorb DH and produce noticeable fluorescence color changes after adsorption of DH vapor. More significantly, the DQ8-CPM shows nice recycling performance on DH detection and adsorption. Meanwhile, a smart gel based on DQ8 (DQ8-G) shows multi-channel response for DH through color, fluorescence, and state changes. The DQ8 shows high selectivity and sensitivity for DH. The detection limit of DQ8 for DH is 8.6 × 10^–7 mol/L. According to the investigation of the DH binding and response mechanism, the synergistic effect between quinoline and naphthalene diimide groups plays an important role in the DH response process. It's a simple and feasible way to develop materials for detection and adsorption of DH through synergistic effects.

Crystalline materials with diastereomerism serve as ideal prototypes for investigating the influence of coordination environments on chemophysical properties. In this study, we synthesized a pair of axial-equatorial isomers [Co(II)(HB(tim^tBu)₃)(cis-dppen)](BF₄)·solv ([HB(tim^tBu)₃]⁻ = hydrotris(3-tertbutyl-2-thioxoimidazol-1-yl)borate; cis-dppen = cis-1,2-bis(diphenylphosphino)ethene; solv = 0.5THF·2H₂O and 2H₂O for ax-CoHS₂P₂ and eq-CoHS₂P₂, respectively), by varying the crystallization temperatures. Despite both diastereoisomers adopting distorted square pyramidal geometries, the bidentate cis-dppen ligand chelates to the central Co(II) either in an axial-equatorial or equatorial-equatorial manner, with a boron-hydrogen binding to the metal center. Magnetic studies reveal differences in g-values between these axial-equatorial isomers. X-band electron paramagnetic resonance spectra suggest rapid equilibrium and potential conformational interconversion in response to temperature changes in solution. Magnetic measurements indicate field-induced slow relaxation of magnetization in this low-spin S = 1/2 system, with spin-lattice relaxations dominated by Raman and quantum tunneling of magnetization mechanisms due to the absence of thermally populated excited states.

We described a Yb(OTf)₃ combined with Pybox ligand catalyzed asymmetric [3+3] cycloaddition of N-vinyl cinnamaldehyde nitrones with activated cyclopropanes to prepare various functionalized 1,2-oxazines in 24%—95% yields and 22%—96% ee. Experimental results revealed that the reaction underwent a domino [3+3] cycloaddition, dealkenylation, and aza-1,4-addition in three steps. The chiral 1,2-oxazine could be obtained in gram scales and easily converted into various 1,2-oxazine scaffolds. The present method features broad substrate scope, good functional group compatibility, three-component domino reaction, and asymmetric [3+3] cycloaddition of N-vinyl nitrones with activated cyclopropanes.

3,3-Disubstituted oxindoles, forming the core of extensive bioactive natural products and drugs, attract tremendous efforts to develop efficient methods for their preparation. Here, a photocatalyst-free approach for the synthesis of 3,3-disubstituted oxindoles via a substrate-photosensitive strategy under visible light was successfully developed. Preliminary mechanistic studies illustrated that isatin-derived imines can be directly excited by visible light to generate strong oxidant states, facilitating subsequent single-electron transfer (SET) processes with Hantzsch esters to afford the corresponding α-amino radical intermediates. Thus, these α-amino radicals promote the subsequent Giese radical addition or radical/radical cross-coupling reactions to furnish diverse functionalized 3-substituted 3-aminooxindoles in high yields.