ACS Organic & Inorganic Au最新文献

Amine rich cyclopentadienyl (Cp^N3) ligands are electronically distinct from classical Cp ligand architectures, as they exhibit fascinating proton-coupled electron transfer (PCET) chemistry under acidic conditions in the presence and absence of transition metals. We now report that the exocyclic N-H bond of the isopropylamine moiety in [^RCp^N3]⁺ can be deprotonated under basic conditions (R = ⁱPr, ^t Bu), enabling the experimental determination of N-H bond strengths via pK _a and redox potential measurements in acetonitrile. From these data, the experimentally determined N-H acidity and bond dissociation free energy of [^iPrCp^N3]⁺ are pK _a = 22.6 and BDFE = 82.6 kcal/mol in acetonitrile. These results are linked with the known C-H bond thermochemistry data of [^iPrCp^N3]⁺, and computational (DFT) data sets are in excellent agreement with experiment. The exocyclic N-H bond acidity was also investigated with [^iPrCp^N3]⁺ coordinated to Fe-(CO)₃, and surprisingly, its pK _a is largely unperturbed in the presence of a transition metal (pK _a = 20-24 (experiment); 23.7 (DFT)). This prompted us to investigate the formal oxidation state of the iron center in our "Fe^II" starting material, with ⁵⁷Fe Mössbauer spectroscopy, XANES spectroscopy, charge distribution via reporter (CDVR) analysis, and computations, revealing that the metal center is best interpreted as having a +2 formal oxidation state. These data suggest that the electronic perturbations at the electron-rich Cp^N3 ligand upon coordination to Fe^II do not significantly influence the exocyclic N-H bond acidity.

Globally, breast cancer is the second leading cause of cancer-related mortality among women. Early detection, accurate diagnosis, and timely treatment are critical for improving survival rates. Therefore, developing a rapid and highly sensitive diagnostic method for early-stage breast cancer detection is essential. Human epidermal growth factor receptor 2 (HER2) is a well-characterized indicator of aggressiveness and poor prognosis in various cancers, including breast cancer. HER2-positive breast cancer represents about 15-20% of all cases, highlighting the significance of HER2 as both a prognostic and predictive biomarker. Gold nanoparticles (AuNPs) have emerged as promising tools in cancer diagnostics due to their unique optical and physicochemical properties. Among these, green-synthesized AuNPs are particularly attractive for biomedical applications due to their eco-friendliness and biocompatibility. Andrographis paniculata is a medicinal herb traditionally employed in the treatment of several diseases. Its leaf extract (ALE) contains various bioactive compounds, including flavonoids and diterpenoids, known for their strong reducing capabilities suitable for AuNP synthesis. In this study, we synthesized AuNPs using ALE (ALE-AuNPs) through a green, one-pot method. The ALE-AuNPs ranged from 11.12 ± 2.10 to 43.53 ± 10.53 nm in size, with a zeta potential of -21.00 ± 0.89 to -44.60 ± 2.36 mV. Cytotoxicity testing on MCF-7 cells indicated good biocompatibility. For targeted detection, the ALE-AuNPs were further functionalized with polyethylene glycol (PEG) and anti-HER2 antibodies, forming ALE-AuNPs+PEG+anti HER2. This nanoconjugate successfully detected HER2-positive MCF-7 cells via a 3,3',5,5'-tetramethylbenzidine-based colorimetric assay. To the best of our knowledge, this is the first report of a simple green synthesis of AuNPs from ALE for use as a colorimetric probe in HER2-positive breast cancer detection.

The reaction of tetraethylammonium polychlorides or polybromides in propionitrile with substoichiometric amounts of diluted fluorine at low temperatures leads to the non-classical interhalogen compounds [NEt₄]-[F-(X₂)₃] (X = Cl and Br). These compounds are the first examples of anions containing a central μ₆ fluoride anion, which is octahedrally surrounded by Br₂ or Cl₂ units, respectively. Single-crystal X-ray diffraction revealed that these compounds crystallize in the cubic system with every fluoride anion bridged by halogen units, resulting in a 3D network. Furthermore, single-crystal Raman and IR spectra were measured, and investigations using solid-state calculations were carried out.

Four water-soluble dendrimers with sumanene or triphenylene cores were obtained with the intended application as molecular receptors. Their water solubilities were found to vary from 46 to 820 μM. Solubility values strongly correlated with free energy of dimerization values calculated using umbrella sampling method (a molecular dynamics-based method.). Moreover, it was found that the fluorescence of two compounds was selectively quenched in the presence of group 13 cations (Al³⁺, Ga³⁺, and In³⁺) in water with nanomolar limit of detection values. Structures of the formed complexes were proposed based on cation-binding site studies by ¹³C-{¹H} NMR spectroscopy. Performance of a selected compound in the analysis of real-life water samples was examined. It was found that the compound was capable of detecting group 13 cation contamination in surface water samples when the organic substance content was low. The obtained compounds are the first known water-soluble sumanene derivatives and the first sumanene derivatives capable of group 13 cation detection.

Hydroxylamine (NH₂OH), an N-O containing moiety and a pivotal intermediate in the nitrogen biogeochemical cycle, typically functions under reducing conditions, in stark contrast to its isoelectronic O-O analogue, hydrogen peroxide (H₂O₂). Oxygen-substituted hydroxylamine derivatives, widely employed in organic synthesis, utilize electron-withdrawing substituents (R) to weaken the N-O bond, thereby enabling the generation of reactive "N-transfer" intermediates. Although these reagents are increasingly recognized for their dual roles as masked "amine" donors and potential "oxidants", direct experimental validation of their oxidative capacity has remained elusive. Herein, we report a detailed mechanistic investigation integrating kinetic, spectroscopic, electrochemical, and computational approaches to establish the dual functionality of O-acyl-substituted hydroxylamine derivatives in iron-catalyzed N-transfer processes. Using a series of O-benzoyloxy hydroxylamine-derived triflic acid salts bearing electronically varied substituents (Ox_Me, Ox_OMe, Ox_H, and Ox_NO2 ) along with the O-pivaloyl hydroxylamine derivative (PivONH₃OTf), (Ox_OPiv), a clear structure-function relationship was uncovered, where the modulation of the electron density on the oxygen substituent tunes the redox potential and thus the oxidizing strength of the O-acyl-substituted hydroxylamine-derived N-O reagents. Mechanistic probing using well-defined outer-sphere Fe-(II) redox probesferrocene (Fc) and decamethylferrocene (DMFc)demonstrates that O-acyl-substituted hydroxylamine derivatives promote Fe-(II) to Fe-(III) oxidation via the outer sphere electron-transfer process. However, while Fc undergoes oxidation to ferrocenium ion (Fc⁺) along with the formation of putative iron-nitrogen/N-inserted intermediates (detected by high-resolution mass spectrometry), the sterically hindered, methyl-substituted DMFc exhibits a pure outer sphere redox event to form decamethylferrocenium ion (DMFc⁺) without competing N-substitution reactivity on the cyclopentadienyl (Cp) backbone. Together, these results provide the first direct experimental evidence for the oxidative capability of O-acyl-substituted hydroxylamine derivatives via a reductive N-O bond cleavage. This study unveils a mechanistically distinct pathway for the advancement of catalytic amination reactions and guides the design of sustainable nitrogen-transfer methodologies.

Oxazolidinones are important heterocyclic compounds with several therapeutic properties, especially antimicrobial activity, as seen in linezolid. Unexpectedly, a 2-oxazolidinone structurally similar to linezolid was obtained, prompting optimization of the reaction methodology and quantum calculations to rationalize the experimental observation. The reaction proceeded efficiently in refluxing water, in which computational analysis identified a remarkable and unprecedented stable reaction intermediate, enabling possible anchimeric assistance. Water significantly accelerates the process by lowering energy barriers and facilitating epoxide ring-opening through hydrogen bonding catalysis, as supported by density functional theory calculations.

Herein, a comprehensive theoretical investigation of the electrocatalytic cycle related to water oxidation (WO) (i.e., the bottleneck of H₂ electrochemical production) catalyzed by a single-site copper-(II) complex bearing the 14-TMC ligand (1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) is presented. Density Functional Theory (DFT) calculations were carried out to characterize two distinct single-electron transfer-water nucleophilic attack (SET-WNA) mechanisms that operate in the O-O bond formation in the electrocatalytic cycle. The electrochemical reaction is initiated with the formation of a [Cu-(14-TMC)-(H₂O)]⁺² intermediate, followed by a proton-coupled electron transfer (PCET) redox transformation. The first PCET is succeeded by a SET or a second PCET, leading to the formation of [Cu-(14-TMC)-(OH)]⁺³ (⁴ 2) or [Cu-(14-TMC)-(O)]⁺² (⁴ 3), the starting reaction intermediates for the two SET-WNA mechanisms proposed. Notably, the presence of HPO ₄ ^2- plays a critical role in promoting the formation of the O-O bond formation. A proton transfer from water to HPO₄ ^2- facilitates the O-O bond formation involving [Cu-(14-TMC)-(OH)]⁺³ (⁴2) and [Cu-(14-TMC)-(O)]⁺² (⁴ 3) species. To reinforce the crucial role of HPO₄ ^2- under neutral conditions, in the absence of this anion, the overall reaction barrier for O-O bond formation is ≈40 kcal/mol, which rules out this reaction pathway at room temperature. Finally, successive PCET or SET steps involving [Cu-(14-TMC)-(HOOH)]⁺² or [Cu-(14-TMC)-(OOH)]⁺ intermediates result in the evolution of the O₂ and regeneration of the catalyst. The thermodynamic and kinetic computational results show good agreement with previous experimental electrochemical data. Overall, based on these computational findings, we propose a new picture for the WO electrocatalytic cycle mediated by macrocyclic Cu complexes bearing the 14-TCM ligand.

Nickel-catalyzed electrochemical cross-coupling has emerged as an important advancement in synthetic chemistry, combining the versatile catalytic properties of nickel with the sustainability and precision of electrochemical methods. This review captures the recent progress in this dynamic field, focusing on developments published from 2015 onward, and emphasizes the development of innovative catalytic systems and reaction conditions that enhance efficiency, selectivity, and environmental sustainability. Key advancements include novel nickel catalysts, expanded substrate scopes, and mechanistic insights that elucidate the synergistic benefits of electrochemical approaches. By exploring these recent developments, we highlight the transformative potential of nickel-catalyzed electrochemical cross-coupling in facilitating complex bond formation under mild conditions. This comprehensive overview provides a foundation for understanding the current state and future directions of this promising area, emphasizing its significance in advancing green and efficient synthetic methodologies.