RSC Mechanochemistry最新文献

Mechanochemical synthesis involves carrying out chemical reactions without solvents and has attracted much attention as green chemistry. Herein, we demonstrate solvent- and catalyst-free mechanochemical synthesis of hypervalent tin(IV) compounds with azo/azomethine tridentate ligands and organotin(IV) oxide by manual grinding in an agate mortar. FT-IR spectra indicate that 41–82% of the ligands can be converted to hypervalent tin compounds depending on the reaction conditions. The resulting products exhibit solid-state emission in the yellow to deep-red region without purification.

We demonstrate solvent-free mechanochemical iodocyclization of tetraaryl[3]cumulenes using N-iodosuccinimides as the first example of the molecular transformation of cumulenes based on mechanochemistry. This mechanochemical reaction provides the corresponding benzofulvenes in good yields, overcoming the limitation of conventional methods using organic solvents.

Singlet oxygen molecules are useful in several therapeutic applications involving photo-activated release of oxygen from carrier molecules toward targeted cells. However, the drawbacks of existing photo-activated methods encourage the development of alternatives, particularly polymer mechanophores that act as oxygen carriers. Here, we present a reactive molecular dynamics simulation-based study of an endoperoxide-based polymer for which oxygen release can be activated either thermally or mechanochemically. Simulations of the polymers heated are compared to simulations of the polymers subject to compression and shear at room temperature. Results show that oxygen release is preceded by deformation of the anthracene ring in both thermal and mechanochemical reactions. However, in the mechanically activated reaction, this deformation is imposed directly by chemical bonding between the oxygen and atoms in the shearing surfaces, eliminating the need for high temperature to initiate the oxygen release. These results could be useful in the development of alternative therapeutic protocols that do not rely on photo-activated reactions.

Various ureido β-cyclodextrins can be easily synthesised by mechanochemistry from azido-β-cyclodextrins, carbon dioxide and amino derivatives. The reaction was carried out with short reaction times, without solvents and without thermal activation, greatly reducing the environmental impact of the synthesis.

The constrained geometries simulate the external force (CoGEF) method mimics the application of external stress on molecules. Herein, we used the CoGEF method at the hybrid density functional theory level to investigate the behavior of silicon carbide nanotubes (SiCNTs) under longitudinal stress. When the SiCNTs are under longitudinal stress, we observe a gradual decrease in the binding energy and the frontier orbital gap with the applied strain until a critical threshold is reached. Beyond this threshold, a sudden increase in both parameters occurs, indicating the formation of some kind of stable structure. The higher binding energy of the larger SiCNTs makes them more resistant to rupture under strain, suggesting their increased mechanical strength. Additionally, we observed a rapid initial increase of Young's modulus of SiCNTs and convergence to a constant magnitude with further increase in their diameter. Therefore, CoGEF analysis provides invaluable insights into the changes occurring in the structural and electronic properties of SiCNTs when subjected to stress.

In order to mitigate the risks associated with cobalt supply, a safe and affordable LiFePO₄-based (LFP) cathode for Li-ion batteries can be a significant solution to meet the rapidly growing battery market. However, economical and environmentally friendly recycling of LFP is impossible with currently available recycling technologies. In this study, an acid-free mechanochemical approach is applied to reclaim Li from LFP using Al as a reducing agent. The reaction mechanism involved in reductive ball-milling followed by water leaching has been elucidated through the examination of various milling times and molar ratios of components, fostering a deeper understanding of the process. Assessing the yield and purity of the final products provides insights into potential enhancements for this technology. Utilizing Al as the material of the current collector eliminates the need for additional external additives, thereby simplifying the recycling workflow. Continued research into this process has the potential to facilitate efficient and economical recycling of LFP materials.

The mechanochemical synthesis of nanomaterials for catalytic applications is a growing research field owing to its simplicity, scalability, and eco-friendliness. In this work, we synthesised new zinc bionanohybrids via a mechanochemical method involving a size effect at the nanoscale and microscale levels of the final nanostructure. This effect translates into an improvement in the catalytic properties of this nanomaterial, such as enzyme-like activities, compared to that synthesized in an aqueous media. One-pot synthesis was performed by combining Candida antarctica lipase B (CALB) solution, solid zinc salts and phosphate or bicarbonate salts using the ball-milling approach, where overall reaction times were drastically reduced in comparison with the traditional aqueous method. The reaction was carried out at r.t. and the synthesis process was evaluated by considering the use of steel balls with different sizes, completely dry conditions or in the presence of a very small amount of water as an additive (2 mL), and incubation methods (planetary or horizontal ball milling). The final nanostructure of the Zn biohybrids was determined using XRD, FT-IR, TEM and SEM analysis, demonstrating changes in metal species and drastic changes in the nanostructure conformation of the biohybrids obtained through the mechanical approach compared to those obtained through the aqueous method. The size effect at the nanoscale was also demonstrated in the final species, showing a reduced size. This nanoscale effect of the material had a positive impact on the catalytic properties of the materials, in some cases showing up to 2000 times greater activity compared to the counterpart synthesised under aqueous conditions.

Novel electrode materials for electrocatalytic hydrogen generation are investigated for increasing the activity of expensive noble-metal components. Here various mixed-metal copper–ruthenium combinations of the metal–organic framework (MOF) HKUST-1 (HKUST = Hong Kong University of Science and Technology, with the formula [Cu₃(BTC)₂(H₂O)₃]_n (BTC = benzene-1,3,5-tricarboxylate)) as Cu_xRu-BTC were synthesized through a mechanochemical method. This mechanochemical method allowed for gram-scale synthesis of the mixed-metal MOFs in a one-hour synthesis time. Characterization through powder X-ray diffraction (PXRD), N₂-adsorption, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Fourier transform infrared (FT-IR) spectroscopy confirmed the formation of a MOF with the HKUST-1 topology, albeit with lower porosity compared to neat HKUST-1. The synthesized MOFs were tested as precursor materials for catalysts for the oxygen evolution reaction (OER) and performed comparably to the industry standard ruthenium oxide (RuO₂). An overpotential (η) of 314 mV (RuO₂η = 312 mV), a Tafel slope (b) of 55 mV dec⁻¹ (RuO₂b = 47 mV dec⁻¹) was achieved which in combination with a charge-transfer resistance (R_CT) of 13.6 Ω (RuO₂R_CT = 52.8 Ω) and a faradaic efficiency (FE) of 70% (RuO₂ FE = 66%) supports the derived catalyst from Cu₁₀Ru-BTC with an intimate mixture of copper and ruthenium at the nanoscale to be effective for the OER having lower ruthenium content than RuO₂. All derived catalysts from the Cu_xRu-BTC samples and RuO₂ showed good stability in a chronopotentiometric measurement over 12 h.

An auxiliary mediated solventless mechanochemical methodology for the nucleophilic aromatic substitution of aryl fluorides by nitrogen nucleophiles without the aid of any base has been developed. The excellent affinity of Al₂O₃ for hydrogen fluoride is the key for this process. Thanks to the use of Al₂O₃ as a milling auxiliary yields of up to 99% were achieved, and the easily processable crude derived from the milling jar allowed a simple and fast work-up procedure, making this method very attractive.

In this study, we developed a simple and efficient method for synthesizing double heterohelicenes (DHHs) composed of two heteroacenes bearing an NH group, such as benzo[b]phenoxazine (BPO) and dibenzo[b,i]phenoxazines (DBPO), using mechanochemical oxidative C–N coupling reactions, allowing complete solvent-free synthesis from commercially available compounds. Our new synthetic method afforded more than 1 g of DHH, which has a high dissymmetry factor for circularly polarized luminescence (g_CPL) of >1 × 10⁻², in a one-pot mechanochemical reaction using BPO as a reactant. In addition, mechanochemical oxidative coupling also allows for further fusion reactions of DHHs, leading to semi- or fully planarized molecules, which have not been previously achieved through solution-phase reactions. We isolated semi-planarized heterohelicenes 5 and 6 and determined their structures using single-crystal X-ray analysis. Compounds 5 and 6 exhibited enhanced electron donor properties compared to DHHs 3 and 4. The enantiomers of 6 exhibited clear CPL emissions with a |g_CPL| value of 2 × 10⁻³. The magnitudes of the transition magnetic dipole moment (TMDM) of 5 and 6 increased compared to those of 3 and 4. Transition moment density analysis revealed that large TMDM densities appeared on the newly formed C–C bonds, providing a unique molecular design guideline for enhancing the magnitude of the TMDM without expanding the molecular structure.