ACS Organic & Inorganic Au最新文献

The influence of the tetra-O-2-oxopropyl-substituted calix-[4]-arene conformation on its binding affinity toward first- and second-group metal cations, as well as on the solvent molecule (acetonitrile or methanol) inclusion in the calixarene hydrophobic cavity, was investigated experimentally and computationally. Misorientation of one monomeric subunit in the partial cone ligand (L _p ) led to incomplete cation desolvation and significantly reduced its cation-binding ability compared to the regular cone isomer (L _c ). Aromatic ring inversion also precluded solvent inclusion in the calixarene basket of both free and complexed L _p (in contrast to L _c ), which considerably affected the complex stabilities and highlighted the pronounced cooperative allosteric effect of this process on the cation binding. Comprehensive structural and energetic studies, carried out by classical molecular dynamics simulations and quantum chemical calculations, showed that inclusion of acetonitrile within the complexes was favored over methanol, whereby the nitrile group of the solvent coordinated the second-group cations. Conversely, the methyl group of included acetonitrile or methanol molecule faced the alkali metal cations in the corresponding adducts. Molecular and crystal structures of free L _p , as well as sodium, calcium, and barium complexes of L _c with included acetonitrile, were determined by single-crystal X-ray diffraction. The orientations of solvent molecules within the calixarene cavity in the solid state closely matched computational predictions, further supporting conclusions drawn from the experimental data. Overall, this work presents a particularly detailed account of the thermodynamic and structural aspects of chelate, macrocyclic, and medium effects on the cation-hosting processes, providing valuable insights into the driving forces governing supramolecular recognition in solution.

In this study, we designed and synthesized a series of novel piano stool ruthenium complexes featuring bulky substituents on the cyclopentadienyl (Cp) ligand to investigate how the substituent structure affects rotational behavior around the Cp-Ru bond. Substituents, including m-xylyl, mesityl, and 9-anthracenyl groups, were introduced to create steric hindrance with the tripodal ligand to increase the rotational barrier. NMR spectroscopy revealed that the Cp-Ru bond in the complex with the m-xylyl group rotated faster than the NMR time scale, whereas complexes bearing mesityl and 9-anthracenyl groups exhibited slower rotation. Variable-temperature NMR measurements and line shape fitting analysis showed that the activation free energy (ΔG ^⧧) required for the Cp ligand rotation by overcoming the steric hindrance between the substituent and tripodal ligand was significantly higher for the mesityl (69.5 kJ mol^-1) and 9-anthracenyl (67.8 kJ mol^-1) complexes compared to the previously reported pentaphenyl Cp complex (18.9 kJ mol^-1). The results indicate that the activation enthalpy is the primary contributor to the overall activation energy, suggesting that the bulky substituents increase the rotational barrier by occupying the spatial gap between the pyrazole rings of the tripodal ligand. This is confirmed by theoretical calculations and the characterization of the minimum energy paths and transition states for each species. These findings offer valuable guidance for the molecular design of STM-operable molecular motors that can function at or near ambient temperature instead of the typical extremely low-temperature conditions necessary to suppress random molecular motion caused by thermal excitation.

Engineered stone (ES) silicosis is emerging as a global occupational health crisis, caused by exposure to respirable particles generated during the processing of ES composite materials. ES composites comprise crystalline silica (predominantly quartz), inorganic aggregates, polymeric resins, and pigments. The severity of lung disease in workers contrasts with the modest effects observed in short-term in vitro studies, exposing a critical gap in our mechanistic understanding of ES dust toxicity. In this work, we examined the surface chemistry and reactivity of ES dust obtained from a slab with high crystalline silica content, before and after incubation (up to two months) in simulated lung fluids: artificial lysosomal fluid (ALF, pH ∼ 4.5) and lung lining fluid simulant (Gamble's solution, GS, pH ∼ 7.4). Damage to model membranes (red blood cell, RBC), an initiating event in ES-induced toxicity, was quantified by membranolytic assay. Pristine ES dust was negligibly membranolytic. Incubation in ALF markedly increased ES membranolytic activity, correlating with partial degradation of the resin. A complete removal of the resin produced a dust with further enhanced activity, associated with the exposure of nearly free silanol (NFS) groups, a recognized molecular trigger of quartz toxicity. NFS were detected by infrared spectroscopy after H/D isotopic exchange. ALF incubation also led to substantial release of transition metal ions, which catalyzed the formation of hydroxyl and carboxyl radicals, detected by EPR spectroscopy. In contrast, GS exposure resulted in minimal membranolytic activity and low radical generation. Our findings suggest that prolonged residence of ES dust in lung cellular environments, particularly lysosomes, promotes resin degradation, exposes reactive silanols, and releases transition metal ions, thereby imparting both membranolytic and oxidative potential. This work provides new molecular insight into ES dust toxicity, emphasizes the urgency of safer occupational practices, and paves the way to safe-by-design strategies for future composite materials.

Silver catalysis has emerged as a versatile tool for C-(sp³)-H bond functionalization, offering unique opportunities to transform simple hydrocarbons into valuable products. Both activated and unactivated C-(sp³)-H bonds have been investigated in recent years. However, most studies have focused on activated bonds. In these protocols, in situ generation of nitrene intermediates has dominated the field, enabling efficient and selective C-(sp³)-H bond transformations. These reports demonstrate that ligand design, in addition to the nature of the silver catalyst, plays a crucial role in achieving chemo-, site-, and even stereoselectivity. During the past decade, silver-catalyzed functionalization has been used for the conversion of C-(sp³)-H bonds into C-C, C-N, C-O, and C-X (X = halogen) bonds. These protocols have shown that Ag-(I) combined with suitable oxidants can be used as a powerful synthetic tool for the functionalization of specific C-(sp³)-H bonds into desired C-Z bonds. This review highlights the advances and limitations in silver-catalyzed C-(sp³)-H functionalization that have been reported during the past decade.

We survey a range of 2D van der Waals (vdW) layered materials that contain homonuclear bonds of main group elements, specifically Ga-Ga, In-In, Si-Si, Ge-Ge, and P-P, using first-principles density functional theory (DFT) methods. The covalent bonding and geometries present in these materials can stabilize oxidation states that differ from those found in conventional semiconductors composed of main group elements, such as Si, InP, and GaAs. Since 2D vdW materials did not gain widespread use until recently, many have been excluded from the first-principles test sets developed over a decade prior, where the focus was on determining the accuracy of potentials used in different modeling methods. In this study, we benchmark the set by exploring a range of modeling methods that include GGA and meta-GGA exchange-correlation functionals commonly used in first-principles DFT methods, as well as exact exchange introduced using HSE06 and PBE0. We investigate their effects on the ground-state structure, electronic band structure, and computational cost and report on this benchmarking data. Our test set of 2D vdW materials contains multiple structural types that span binary, ternary, and quaternary compositions, including ferroic ground states. We found that the vdW-corrected GGA is capable of accurately capturing lattice constants (within ±2% relative to available experimental data) across various 2D vdW materials in our test set, with relatively low computational cost and turn-key compatibility with the open-source code Quantum Espresso. Additionally, vdW-corrected GGA can reliably identify stable ferroelectric and ferromagnetic ground states, can be used to determine trends in electronic band structure, and serve as a starting point for predicting more accurate band gaps. The predicted electronic band structure and corresponding projected density of states (PDOS) are crucial for establishing the connection between microscopic properties and atomic or molecular orbitals, which can, in turn, be used to predict novel functional 2D vdW materials.

Propionate side chains are essential structural components of porphyrin-based metalloenzymes. While numerous studies have investigated the functional significance of propionate side chains from various perspectives, comprehensive reviews focusing specifically on their roles in catalytic mechanisms remain scarce. Traditionally, the role of propionate has been limited to substrate binding and heme stabilization; however, emerging evidence from studies published particularly after 2005 highlights its involvement in a range of noncanonical functions, including water gating, oxidant formation, and electron transfer. This review aims to bridge the gap in existing literature by systematically discussing these expanded roles and emphasizing the broader mechanistic importance of propionate side chains in metalloenzymes, particularly the iron-containing enzymes.

This review comprehensively summarizes the recent advances in the direct C-H perfluoroalkyl thiolation and perfluoroalkyl sulfonylation, focusing on the incorporation of -SCF₃ and -SO₂CF₃ motifs. Due to their exceptional lipophilicity, electron-withdrawing nature, and metabolic stability, these fluorine-containing groups are highly valuable in pharmaceutical, agrochemical, and material sciences. The contents of this review are systematically organized according to the hybridization of the central carbon atom (sp, sp², sp³) and cover both transition-metal-catalyzed and transition metal-free methodologies. Key developments in electrophilic trifluoromethylthiolating reagents, such as hypervalent iodine compounds, N-trifluoromethylthiosaccharin, and related derivatives, are highlighted. The mechanism, scope, limitation, and application of typical reactions are discussed, emphasizing strategies to overcome challenges in regioselectivity and functional group compatibility. The review also explores emerging trends in photocatalytic, electrochemical, and dual catalytic systems, underscoring the move toward more sustainable and efficient synthetic routes. Finally, future perspectives and potential applications in the synthesis of bioactive molecules and functional materials are discussed.

Taming radical anions with highly electropositive metal ions poses a grand synthetic challenge owing to the high reactivity of such compounds originating from the unpaired electron. A successful synthetic metal radical match elicits a desire to thoroughly understand the electronic structure of a given metal radical pairing, which may inform about the potential physical properties pertaining to spintronics and magnetism relevant for future technologies. Here, the 1,4,5,8-tetraazanaphthalene (tan) ligand was utilized in the synthesis of (Cp*₂Y)₂(μ-tan), 1, using the doubly reduced version K₂tan and Cp*₂Y-(BPh₄) following a salt metathesis reaction. Chemical oxidation of 1 yielded [(Cp*₂Y)₂(μ-tan^•)]-[BArF₂₀], 2, containing a tan^-• radical anion. 2 constitutes the first d-block coordination compound bearing a tan radical. 1 and 2 were studied through X-ray crystallography, electrochemistry, and spectroscopy. The radical nature of 2 was uncovered by cw-EPR spectroscopy and density functional theory (DFT) computations. All findings suggest major changes in the spin and charge distributions of this organic radical ligand when it is metalated. In fact, the results demonstrate that the tan^-• radical is more stable when coordinated to a transition metal than in its free nature, and thus, this insight is relevant for the development of future spintronic technologies.

The use of heterogeneous catalysts to generate amine compounds through anaerobic N-alkylation of alcohols via hydrogen transfer strategy is a highly promising synthetic strategy, as it can construct C-N bonds under relatively mild and green conditions. Moreover, amine compounds are widely used in the synthesis of pharmaceutical intermediates, agriculture and fine chemicals. In this work, we successfully constructed a novel Co₃O₄/CeO₂ catalyst using the hydrothermal synthesis method and applied it to the N-alkylation reaction of alcohols, achieving up to 99% of the target product yield with broad substrate scope and high catalyst stability. The Ce³⁺/Ce⁴⁺ redox pairs and oxygen vacancies in the CeO₂ support with highly dispersed Co species synergistically catalyze the hydrogen borrowing process of alcohols and amines to generate secondary amines with high activity and selectivity.

We report the design, synthesis, and conformational analysis of two aryl-extended calix[4]-pyrrole (AE-C[4]-P) cavitands that feature a single methylene bridge and an opposed aromatic bridging wall with an inward-facing carboxylic acid. Inspired by Rebek's introverted acid motif, these cavitands were developed to explore guest-induced conformational switching between "equatorial" and "axial" orientations of the bridging aromatic wall. Binding studies with N-oxide guests, capable of monotopic or ditopic hydrogen bonding, revealed that the nature of the bridging aromatic spacer critically governs the host behavior. The benzimidazole-based cavitand showed strong affinity for DABCO mono-N-oxide but resisted conformational change. In contrast, the quinoxaline-imidazole analogue underwent a solvent-dependent switch from "equatorial" to "axial" geometry upon binding 4-carboxy-pyridine-N-oxide guest. This switching is driven by the ditopic binding of the guest and stabilized by two intramolecular CH···lone pair interactions in the axial conformer of the complex. DFT calculations supported the experimental results. The reported findings highlight key structure-function relationships in calix[4]-pyrrole cavitands and establish a general strategy for designing guest-responsive molecular containers capable of conformational switching.