Applied Organometallic Chemistry最新文献

Several racemic zirconium complexes 1–8 featuring [NOON]-type ligands were synthesized through alkane elimination reactions between Zr(CH₂SiMe₃)₄ and the respective new proligands in toluene. Spectral and elemental analyses were used to characterize these complexes, which demonstrated good performance in rac-lactide polymerization. All complexes displayed comparable catalytic activity, with 5 exhibiting the highest activity (TOF = 58.7 h⁻¹) and 8 yielding polylactide with the highest molecular weight (M_n = 8.6 × 10⁴ g/mol). Notably, these systems outperform existing zirconium complexes bearing [NSSN]-type, [OSSO]-type, and ethylene-bridged [ONSO]-type ligands, as well as phosphasalen Ti/Zr complexes, under analogous polymerization conditions. To enhance the stereoselectivity of these systems, four co-agents—pyridine, 2,2′-bipyridine, DME, and TMEDA—were evaluated. TMEDA was found to significantly improve the stereocontrol of all complexes, with complex 2 showing the highest stereoregularity (P_m = 0.72).

The geometric structures and electronic properties of three experimentally reported anticancer Pt (II), Au (III), and Cu (II) complexes (named complexes 1–3) as well as the interactions of these complexes with biological target molecules have been explored in detail by density functional theory (DFT) calculations. Significant differences in the polarity of M-Cl (M = Pt, Au, and Cu) bonds and the nucleophilic reactivity of metal centers were revealed for these complexes. Further research shows that the differences in the hydrolysis and the ligand exchange reactions with biological targets of these complexes are the main reasons for their different antitumor activities. Based on these findings, four novel complexes 4–7 have been rationally designed by replacing the Cu (II) center of 3 with Ni (II), Zn (II), Pd (II), and Fe (II) ions for the first time. Therein, the obtained Zn (II)–centered complex 5 is predicted to exhibit the highest similarity to complex 3. This study not only provides a profound theoretical insight into the activity difference of the reported metal complexes from molecular level but also proposes an effective strategy to design new anticancer drugs.

An eco-friendly, visible-light-driven synthesis of benzamides from readily accessible benzonitriles is reported under heterogeneous conditions. A carbon-rich material, such as polyhexahydrotriazine (PHT), graphene oxide (GO), graphitic nitride (g-C₃N₄)or carbon black, was used as a novel support to stabilise silver nanoparticles (NPs). These silver NPs show remarkable catalytic activity in the hydration of nitriles under visible light irradiation (white light, 9 W). Furthermore, silver NPs stabilised by a triazine moiety exhibit better performance than other supported silver systems, including graphene oxide and carbon black. Their stability and heterogeneous nature as catalysts have been demonstrated through three cycles of recycling in the synthesis of benzamides. This approach utilises mild visible light and a recyclable catalyst that efficiently converts benzonitriles to amides in excellent yields. This work provides a sustainable approach to amide synthesis. Density functional theory (DFT) calculations further indicate that the binding energy of 4-bromobenzonitrile (BCN) to Ag@C₃N₄ is −31.50 kcal/mol. Further triphenyl phosphine poisoning test confirms the heterogeneous nature of our catalyst under visible light.

A series of Fe^III complexes [Fe(5-Br-3-MeO-sal₂Trien)]Y·Z (Y = NO₃⁻, Z = 0.5CH₃OH·CH₃CN (1); Y = NO₃⁻ (2); Y = ClO₄⁻ (3)) have been prepared. Complexes 1 and 2 exhibit analogous crystal packing architectures with two distinct iron centers, labeled Fe1 and Fe2. The Fe1 sites form dimers encapsulated within a hexagonal framework constructed by Fe2 centers. Thermal expansion of the Fe2 framework upon heating creates sufficient space to facilitate the spin transition of Fe1. Both complexes display similar one-step gradual spin crossover behavior, with transition temperatures (T_c) of 142 K for 1 and 186 K for 2, respectively. In contrast, complex 3 incorporates four crystallographically independent Fe centers. Its overly compact packing geometry sterically hinders spin-state switching, resulting a partial low-spin state over the entire tested temperature range.

In this study, we used Lobelia chinensis leaves to describe biogenically supported iron nanoparticles. The leaf of Lobelia chinensis was utilized as an excellent stabilizer for the iron nanoparticles that were synthesized. The as-synthesized Fe NPs@Lobelia chinensis were physicochemically characterized using FE-SEM, FT-IR, XRD, EDX, and UV–Vis. The DPPH technique was used to assess the antioxidant efficacy of nanoparticles. Based on the IC₅₀ value, the antioxidant activity of the Fe NPs@Lobelia chinensis was significant. Because of their antioxidant qualities, recent nanoparticles seem to have an antihuman endometrial carcinoma potential. Fe NPs@Lobelia chinensis that was biologically produced was evaluated for their anti-endometrial cancer properties against endometrial cancer cells. By using the MTT assay, the anti-endometrial cancer characteristics of the Fe NPs@Lobelia chinensis could effectively eliminate HEC-1-B cancer cells. In contrast to their corresponding control, Fe NPs@Lobelia chinensis prevented colony formation. Crucially, the molecular pathway analysis of cells exposed to Fe NPs@Lobelia chinensis revealed that the particles increased the expression of p53 while suppressing the production of phosphorylated and total STAT3 in cells. This suggests that STAT3 and p53 are the primary players behind the medical events that the extract triggered in endometrial carcinoma cells.

Given the adverse effects of conventional chemotherapeutic agents, natural compounds and biocompatible materials have garnered growing interest in cancer therapy. Our previous research demonstrated that zinc oxide nanoparticles (ZnO NPs), synthesized through an ultrasound-mediated green method using coffee leaves, functioned as effective nanocarriers for the controlled release of mangiferin (MGF). Here, we investigated the anticancer activity of MGF, ZnO NPs, and MGF-loaded ZnO NPs (MGF-ZnO NPs) on HepG2 and Caco-2 cells, along with their underlying anticancer mechanisms. We found that both ZnO NPs and MGF-ZnO NPs significantly reduced cell viability and increased the extracellular to intracellular pH ratio (pHe/pHi) and reactive oxygen species levels in HepG2 and Caco-2 cells. MGF-ZnO NPs further induced notable morphological changes and enhanced cell membrane permeability, chromatin condensation, and nuclear lysis. Additionally, both ZnO NPs and MGF-ZnO NPs increased the overall apoptotic rate in cancer cells, with MGF enhancing the cytotoxic effects of MGF-ZnO NPs. Molecular docking analysis revealed that MGF-ZnO NPs may disrupt cell membrane biogenesis by inhibiting the biological activity of choline/ethanolamine phosphotransferase 1 (CEPT1), an enzyme involved in phospholipid synthesis, through hydrogen bonding and hydrophobic interactions. Additionally, MGF-ZnO NPs also exhibited strong binding affinity to DNA bases through hydrogen bonds (DC15(B) and DG12(A)) and hydrophobic interactions (DC23(B), DG22(B), DA18(B), DA17(B), and others), potentially compromising DNA function. This study suggests that loading ZnO NPs with MGF is a promising approach to enhance cancer therapy and underscores the complex mechanisms involved in nanotherapeutic action.

Green hydrogen serves as a crucial renewable energy source driving the transition of energy structures and advancing sustainable development. Photocatalytic technology represents one of the prominent approaches for green hydrogen production. Compared to traditional semiconductors, noble metal single-atom catalysts (SACs) have emerged as promising photocatalysts due to their high atomic utilization efficiency and superior catalytic activity. In this work, Pt and Pd single atoms were separately anchored onto oxygen vacancies (Vo) on the TiO₂ surface via a facile photodeposition method, yielding Pt or Pd monometallic single-atom loaded catalysts (Pt SAs/Vo-TiO₂ and Pd SAs/Vo-TiO₂). The optimal photodeposition time was investigated. Results demonstrate that the hydrogen evolution rate of Pt SAs/Vo-TiO₂ reached 2375.76 μmol h⁻¹ g_cat.⁻¹, while that of Pd SAs/Vo-TiO₂ achieved 1875.72 μmol h⁻¹ g_cat.⁻¹. These values are 76.5-fold and 60.4-fold higher than that of pristine TiO₂, respectively. Density functional theory (DFT) calculations reveal that the introduction of single atoms reduces the band gap of the catalyst, consistent with the experimental findings. This study provides optimal parameters for synthesizing efficient single-atom catalysts.

Chromium is an essential trace element that exerts antidiabetic effects by enhancing insulin sensitivity and upregulating key proteins and genes involved in glucose uptake and metabolism. The antidiabetic potential of chromium nanoparticles (CrNPs) and Adiantum capillus-veneris has been studied separately; however, the conversion of chromium into biogenic CrNPs using the plant extract and the evaluation of their effects on carbohydrate-hydrolyzing enzymes remain unexplored. In this study, CrNPs were synthesized using A. capillus-veneris extract, characterized through various instrumental techniques and evaluated for their antioxidant and antidiabetic potential in vitro. The optimal synthesis was achieved at a 4:9 (v/v) ratio of plant extract to chromium salt. The synthesized CrNPs were crystalline, irregular to round in shape, with sizes ranging from 58 to 90 nm, thermally stable up to 280°C, and exhibited a strong absorbance peak in the UV–Vis range at 420 nm. EDX analysis confirmed the presence of chromium at ~0.6 keV. The resulting CrNPs showed excellent antioxidant (DPPH, IC₅₀ = 100 μg/mL; ABTS, IC₅₀ = 125 μg/mL) and notable inhibition of carbohydrate-hydrolyzing enzymes; α-amylase (91.3% inhibition at 1000 μg/mL, IC₅₀ = 127 μg/mL) and α-glucosidase (86.4% inhibition at 1000 μg/mL, IC₅₀ = 140 μg/mL). CrNPs exhibited stronger biological potentials and outperformed both the aqueous and methanolic extracts of A. capillus-veneris plant, as well as chromium chloride hexahydrate in the antioxidant and antidiabetic assays. In conclusion, these activities are likely due to enhanced bioavailability and polyphenol–enzyme interactions, which significantly improved the activity of chromium chloride hexahydrate upon its conversion into CrNPs. Further validation in experimental diabetic models is warranted.

Photochromic dysprosium single-molecule magnets (Dy-SMMs) not only possess excellent intrinsic magnetic properties but also facilitate the preparation of intelligent devices owing to the integration of photochromism. However, related cases are still limited up to now. Herein, we report two photochromic polynuclear Dy-SMMs, [Et₃NH][Dy₄(ana)₉(OH)₄(CH₃CN)₂(H₂O)]·solvents (1; Hana = anthracene-9-carboxylatic acid) and [Et₃NH]₂[Dy₆(Tox)₄(aca)₁₂(OH)₂(CH₃OH)₂]·solvents (2; Tox⁻ = N-TEMPO oxamate ion). They have tetrahedral [Dy₄(OH)₄]¹²⁺ and double-layered cage-like [Dy₆(Tox)₄ (OH)₂]¹²⁺ cores, respectively, which are ligated by ana⁻ ligands into tetra- and hexa-nuclear cluster structures. Both 1 and 2 exhibit zero-field single-molecule magnet (SMM) behavior featuring a single magnetic relaxation process, which evolved into dual-relaxation processes upon the application of external dc fields. They also exhibit expected photochromic behaviors. The emergence of new peaks in the UV–Vis spectra and the quenching of photoluminescence (PL) emission peaks suggest that their photochromism could be attributed to the photogeneration of radical species in the systems.

The Pd-PEPPSI-NHC complexes (PEPPSI = pyridine-enhanced precatalyst preparation stabilisation initiation, NHC = N-heterocyclic carbene) have been widely applied in the Pd-catalyzed cross-coupling reactions. Further studies on the structures of Pd-PEPPSI-NHC complexes have shown that not only the NHCs, the ancillary ligands surrounding the Pd centre also play important roles in their catalytic reactions. For this purpose, a series of Pd-PEPPSI-NHC analogues bearing cycloalkane ring-fused pyridines (CA-Py) as the ancillary ligand were readily prepared and characterized by ¹H NMR, ¹³C NMR, elemental analysis and x-ray crystallography. The catalytic activities of the well-defined Pd–NHC complexes have been evaluated with respect to Suzuki–Miyaura cross-coupling reactions of aryl boronic acids with aryl chlorides and acyl chlorides, respectively.