Search Results (260)

In the field of green chemistry, the development of more sustainable and cost-efficient methods for synthesizing primary amines is of paramount importance, with catalyst research being central to this effort. This work presents a facile, aqueous-phase synthesis of highly active cobalt catalysts (Co-Ph@SiO₂(x)) via pyrolysis of silica-supported cobalt–phenanthroline complexes. The optimized Co-Ph@SiO₂(900) catalyst achieved exceptional performance (>99% conversion, >98% selectivity) in the reductive amination of acetophenone to 1-phenylethanamine using NH₃/H₂. Systematic studies revealed that its exceptional performance originates from the in situ pyrolysis of the cobalt–phyllosilicate complex. This process promotes the uniform distribution of metal cobalt nanoparticles, simultaneously enhancing porosity and imparting bifunctional (acidic and basic) properties to the catalyst, resulting in outstanding catalytic activity and selectivity. The catalyst demonstrated broad applicability, efficiently converting diverse ketones (aryl-alkyl, dialkyl, bioactive) and aldehydes (halogenated, heterocyclic, biomass-derived) into primary amines with high yields (up to 99%) and chemoselectivity (>40 examples). This sustainable, non-noble metal-based catalyst system offers significant potential for industrial primary amine synthesis and provides a versatile tool for developing highly selective and active heterogeneous catalysts. Full article

The development of high-performance adsorbent materials is crucial for any sorption-based energy conversion process. In such a context, composite sorbent materials, although promising in terms of performance and stability, are often challenging to shape into complex geometries. Additive manufacturing, also known as 3D printing, has emerged as a powerful technique for fabricating intricate structures with tailored properties. In this paper, an innovative three-dimensional structure, constituted by zeolite as filler and sulfonated polyether ether ketone as matrix, was obtained using additive manufacturing technology, which is mainly suitable for sorption-based energy conversion processes. The lattice structure was tailored in order to optimize the synthesis procedure and material stability. The complex three-dimensional lattice structure was obtained without a metal or plastic reinforcement support. The composite structure was evaluated to assess its structural integrity using morphological analysis. Furthermore, the adsorption/desorption capacity was evaluated using water-vapor adsorption isobars at 11 mbar at equilibrium in the temperature range 30–120 °C, confirming good adsorption/desorption capacity. Full article

Siloxane bond formation represents a fundamental reaction central to both silicone chemistry and its technological applications. This paper presents a novel ketone-assisted process for the condensation of alkoxy-functional silanes catalyzed by a cationic Ge(II) complex stabilized by pentamethylcyclopentadiene Cp*Ge(II)⁺. This process leads to the formation of siloxane bonds, with dialkoxy ketal as a byproduct. Unlike the analogous reaction involving aldehydes, the ketone-assisted process is reversible, resulting in the formation of a mixture of alkoxy-functionalized silane or siloxane, along with the corresponding disiloxane product. Additionally, the introduced ketone underwent only partial conversion to the corresponding ketal. Furthermore, it was demonstrated that the siloxane bond could be cleaved to form alkoxysilane in the presence of the ketal and a cationic Cp*Ge(II) complex acting as a catalyst. Full article

Searching for new and efficient transfer hydrogenation catalysts, a series of new organometallic ruthenium(II)-arene complexes of the formulae [Ru(η⁶-p-cymene)(L)Cl][PF₆] (1–8) and [Ru(η⁶-p-cymene)(L)Cl][Ru(η⁶-p-cymene)Cl₃] (9–11) were synthesized and fully characterized. These were prepared from the reaction of pyridine–quinoline and biquinoline-based ligands (L) with [Ru(η⁶-p-cymene)(μ-Cl)Cl]₂, in 1:2 and 1:1, metal (M) to ligand (L) molar ratios. Characterization includes a combination of spectroscopic methods (FT-IR, UV-Vis, multi nuclear NMR), elemental analysis and single-crystal X-ray crystallography. The pyridine–quinoline organic entities encountered, were prepared in high yield either via the thermal decarboxylation of the carboxylic acid congeners, namely 2,2′-pyridyl-quinoline-4-carboxylic acid (pqca), 8-methyl-2,2′-pyridyl-quinoline-4-carboxylic acid (8-Mepqca), 6′-methyl-2,2′-pyridyl-quinoline-4-carboxylic acid (6′-Mepqca) and 8,6′-dimethyl-2,2′-pyridyl-quinoline-4-carboxylic acid (8,6′-Me₂pqca), affording the desired ligands pq, 8-Mepq, 6′-Mepq and 8,6′-Me₂pq, or by the classical Friedländer condensation, to yield 4,6′-dimethyl-2,2′-pyridyl-quinoline (4,6′-Me₂pq) and 4-methyl-2,2′-pyridyl-quinoline (4-Mepq), respectively. The solid-state structures of complexes 1–4, 6, 8 and 9 were determined showing a distorted octahedral coordination geometry. The unit cell of 3 contains two independent molecules (Ru-3), (Ru′-3) in a 1:1 ratio, due to a slight rotation of the arene ring. All complexes catalyze the transfer hydrogenation of acetophenone, using 2-propanol as a hydrogen donor in the presence of KOiPr. Among them, complexes 1 and 5 bearing methyl groups at the 8 and 4 position of the quinoline moiety, convert acetophenone to 1-phenylethanol quantitatively, within approximately 10 min with final TOFs of 1600 h⁻¹. The catalytic performance of complexes 1–11, towards the transfer hydrogenation of p-substituted acetophenone derivatives and benzophenone, ranges from moderate to excellent. An inner-sphere mechanism has been suggested based on the detection of ruthenium(II) hydride species. Full article

Cannabis sativa L. exhibits a complex sensory profile governed by a diverse range of volatile and non-volatile compounds. Volatile constituents—such as terpenes, aldehydes, ketones, esters, and sulfur-containing compounds—together with non-volatile taste-active molecules including flavonoids and phenolic compounds, underlie its distinctive aroma and flavor. This review examines how genetic diversity, cultivation practices, and post-harvest processing modulate the synthesis, accumulation, and chemical transformation of these metabolites in the cannabis flower. It discusses recent advancements in the extraction, identification, and quantification of these compounds, highlighting the crucial integration of chemical characterization with sensory evaluation. By synthesizing findings from advanced analytical methodologies, this review addresses the challenges and opportunities involved in defining the sensory profiles of C. sativa L. varieties. Drawing insights from research on other consumer plants, strategies for future innovations are outlined, including the discovery of novel aroma and flavor compounds and the development of a universal cannabis aroma and flavor wheel. This work aims to support advancements in breeding programs, enhance product quality control, and guide future research in cannabis sensory science. Full article

This study investigates the structural and energetic properties of hydrogen-bonded complexes between indole and a range of aliphatic, cyclic, and aromatic ketones using a combined vibrational spectroscopic and quantum-chemical approach. FTIR measurements in CCl₄ revealed redshifts in the N-H stretching vibration of indole upon complexation, with formation constants (K_a) ranging from 0.3 to 6.6 M⁻¹. Cyclohexanone displayed the strongest binding, while benzophenone exhibited the weakest interaction. Quantum-chemical calculations, employing CREST and MMFF94 conformational sampling, along with M06-2X/6-311++G(d,p) optimizations, confirmed the formation of hydrogen bonds and additional weak interactions that govern the stability of the complex. QTAIM analysis revealed moderate closed-shell hydrogen bonds with electron densities at the bond critical points (ρ) ranging from 0.010 to 0.019 a.u. and potential energy densities (V) from −18.4 to −36.4 kJ mol⁻¹. Multivariate regression analysis established strong correlations (R² = 0.928 and 0.957) between experimental binding constants and theoretical descriptors, including binding energy, NBO charge on oxygen atom, ionization potential, and electrophilicity index, highlighting the interplay between geometric, electronic, and global reactivity factors. This comprehensive study underlines the predictive power of spectroscopic and quantum descriptors for assessing hydrogen bonding in biologically relevant systems. Full article

The purpose of this study was to investigate the effect of different drying methods on the structure and properties of semicrystalline polymer aerogels. Aerogels, consisting of either globular or strut-like morphologies, were prepared from poly(ether ether ketone) (PEEK) or poly(phenylene sulfide) (PPS) and dried using vacuum drying, freeze-drying, or supercritical CO₂ extraction. Vacuum drying was found to result in aerogels with a higher shrinkage, smaller mesopores (with pore widths of 2–50 nm), and smaller surface areas compared to the use of supercritical extraction as the drying method. Freeze-dried aerogels tended to have properties between those of vacuum-dried aerogels and aerogels prepared with supercritical extraction. High network connectivity was found to lead to improved gel modulus, which increased the ability of aerogels to resist network deformation due to stresses induced during drying. The PEEK and PPS aerogel networks consisting of highly connected strut-like features were considerably stiffer than those composed of globular features, and thus shrank less under the forces induced by vacuum drying or freeze-drying. The aerogels prepared from PPS were found to have larger mesopores and smaller surface areas than the aerogels prepared from PEEK. The larger mesopores of the PPS aerogels induced lower capillary stresses on the aerogel network, and thus shrank less. This work demonstrates that preparing PEEK and PPS gels with strut-like features can allow aerogel processing with simpler evaporative drying methods rather than the more complex supercritical drying method. Full article

This study investigated changes in microbial communities and functional components during the fermentation of traditional Korean grain vinegars collected from various regions as well as the correlations among these components. Microbial community analysis revealed that Lactobacillus acetotolerans was the dominant microorganism, while Acetobacter pasteurianus numbers gradually increased during fermentation, playing a key role in acetic acid production. L. acetotolerans, known to thrive in acidic environments, contributed to increasing the acidity of the vinegar and enhanced its preservative properties. The rise in the levels of organic acids, particularly acetic acid, was influenced by the activity of these microorganisms. Additionally, the production of free amino acids, such as alanine, was influenced by interactions between the fermentation medium and microbial communities, significantly contributing to the vinegar’s sweetness. Volatile flavor compounds exhibited considerable diversity due to changes in microbial communities driven by raw-material differences. In particular, five-grain vinegar (YO) tended to generate more complex and intense flavor compounds, with uniformly elevated levels of aldehydes, acids, and ketones. These findings suggest that raw-material selection and fermentation conditions significantly influence the flavor and functional properties of grain vinegars, providing valuable foundational data for improving vinegar production processes to enhance flavor and functionality. Full article

Poly-ether ether ketone (PEEK) is a high-performance thermoplastic known for its excellent mechanical properties, making it relevant for aerospace and medical applications. Additive manufacturing (AM) represents a critical step towards integrating PEEK into these sectors, particularly for complex geometries and custom parts. However, the mechanical properties achieved through AM have not yet reached those obtained via conventional techniques. Recent studies have sought to optimize the printing parameters to bridge this gap, but their findings remain inconsistent and difficult to generalize—suggesting a strong dependence on the experimental conditions. This is partly due to the Fused Filament Fabrication of PEEK being an emerging technology, with many studies relying on in-house built printers. Moreover, the underlying microstructural mechanisms governing its performance have rarely been explored in depth. In this work, we establish clear processing–structure–property relationships by integrating a rigorous DoE approach with comprehensive microstructural characterization. Our results highlight the dominant role of the processing environment near the glass transition temperature in promoting chain mobility, enhancing the amorphous phase ordering, and improving the mechanical performance: crystallinity alone does not fully explain the mechanical behavior of additively manufactured PEEK. Further, higher nozzle temperatures lower the porosity and increase the filament bonding, while faster printing speeds reduce the crystallinity and increase the porosity, negatively affecting the mechanical integrity. The results of this study are generalizable to any FFF printer of PEEK. Other materials or printing technologies are out of the scope of this work. Full article

Over the past few decades, awareness has risen substantially about the limitations of non-renewable resources and the environmental challenges facing the chemical industry. This has necessitated a transition toward renewable resources, such as lignocellulosic biomass, which is among the most abundant renewable carbon sources on the planet. Lignocellulosic biomass represents a significant yet often underutilized source of fermentable sugars and lignin, with potential applications across multiple sectors of the chemical industry. The formation of humins (polymeric byproducts with a complex conjugated network, comprising furanic rings and various functional groups, including ketones) occurs inevitably during the hydrothermal processing of lignocellulosic biomass. This study presents the use of humin byproducts derived from soybean peels for the production of fluorescent carbon dots (CDs). A comparison between sonochemical and thermochemical methods was conducted for the synthesis of this nanomaterial. The obtained nanoparticles were characterized in terms of size, morphology (TEM, DLS), and Z-potential. Subsequently, the spectroscopic properties of the prepared CDs were studied using absorption and emission spectroscopy. In particular, the CDs displayed a blue/cyan fluorescence under UV irradiation. The emission properties were found to be dependent on the excitation wavelength, shifting to longer wavelengths as the excitation wavelength increased. The carbon dots that exhibited the most favorable photochemical properties (QY = 2.5%) were those produced through a sonochemical method applied to humins obtained from the dehydration of soybean husks with phosphoric acid and prior treatment. Full article

Two tetranuclear complexes were obtained by a self-assembly process employing di-2-pyridyl ketone ((py)₂CO), benzoate and M(NO₃)₂ (M = Co and Ni). The compounds [M₄{(py)₂C(OH)O}₄(O₂CPh)₄], where {(py)₂C(OH)O}⁻ is the monoanion of the gem-diol form of (py)₂CO, were characterized through single-crystal X-ray diffraction and magnetic measurements. Structural analysis revealed that both complexes possess a [M₄O₄] cubane-like core. A two-J model and magnetic anisotropy were employed to analyze the magnetic properties of both compounds. These studies indicate the presence of dominant ferromagnetic interactions within both tetranuclear cores. DFT and CASSCF/NEVPT2 calculations were also performed to support the fitting of experimental magnetic data. Full article

In the field of sustainable energy conversion and storage technologies, copper-based complexes have become a research hotspot due to their efficient and stable catalytic performance. The development of bifunctional catalysts that can simplify catalytic steps, enhance efficiency, and reduce catalyst usage has become an important research area. In this study, we successfully synthesized two copper complexes with different geometries utilizing di(2-pyridyl) ketone as the ligand, [Cu^II₂L₂Cl₂]·0.5H₂O (1) and [Cu₄^IIL₄(OCH₃)₂](NO₃)₂ (2) (L = deprotonated methoxy-di-pyridin-2-yl-methanol), which can serve as homogeneous electrocatalysts for water oxidation and CO₂ reduction simultaneously. The turnover frequency (TOF) of complexes 1 and 2 for electrocatalytic water oxidation are 7.23 s⁻¹ and 0.31 s⁻¹ under almost neutral condition (pH = 8.22), respectively. Meanwhile, the TOF of complexes 1 and 2 for the catalytic reduction of CO₂ to CO are 4.27 s⁻¹ and 8.9 s⁻¹, respectively. In addition, both complexes remain essentially unchanged during the electrocatalytic water oxidation and electrocatalytic CO₂ reduction processes, demonstrating good stability. Structural analysis reveals that the distinct catalytic efficiencies originate from their geometric configurations: the binuclear structure of complex 1 facilitates proton-coupled electron transfer during water oxidation, whereas the tetranuclear architecture of complex 2 enhances CO₂ activation. Complexes 1 and 2 represent the first two copper molecular electrocatalysts capable of catalyzing both water oxidation and CO₂ reduction. The findings in this work can open up new avenues for the advancement of artificial photosynthesis simulation and the development of bifunctional catalysts for water oxidation and CO₂ reduction. Full article

A series of novel NNN pincer manganese complexes based on pyrazole skeleton 4 were efficiently synthesized in a two-step process. All of the new complexes were fully characterized by ¹H, ¹³C NMR spectra. Furthermore, the molecular structures of complexes 4a and 4c were also determined by X-ray single-crystal diffraction. The manganese(I) catalysts obtained showed efficient catalytic activity in the α-alkylation reaction of ketones with alcohols. Under optimal reaction conditions, the expected products were procured with moderate to high yields. Full article

Traditional tomato-braised beef brisket with potatoes is celebrated for its rich, complex flavors and culinary appeal but requires lengthy preparation. Pre-packaged versions of the dish rely on thermal sterilization for safety; however, high-temperature processing accelerates protein and lipid oxidation, thereby compromising its sensory quality. As the demand for ready-to-eat meals grows, the food industry faces the challenge of ensuring microbial safety while preserving flavor integrity. In this study, low-temperature plasma sterilization (LTPS) (160 KV, 450 s) was evaluated as a non-thermal alternative to conventional high-temperature short-time (HSS) sterilization. Furthermore, a comprehensive analysis was conducted over a 10-day storage period, assessing microbial viability, physicochemical properties (pH, shear force, and water-holding capacity), oxidative markers (TBARS, TVB-N, and protein carbonyls), volatile compounds (GC-MS), and electronic nose (e-nose) responses. The results revealed that LTPS (160 kV, 450 s) successfully maintained bacterial counts below regulatory limits (5 lg CFU/g) for 72 h, ensuring that the microbial indicators of short-term processed products sold to supermarkets through cold chain logistics were in the safety range. Additionally, LTPS-treated samples showed a 4.2% higher water-holding capacity (p < 0.05) during storage, indicating improved preservation of texture. Furthermore, LTPS-treated samples exhibited 32% lower lipid oxidation (p < 0.05) and retained 18% higher sulfhydryl content (p < 0.05) compared to HSS, indicating reduced protein oxidation. GC-MS and e-nose analyses showed that LTPS preserved aldehydes and ketones associated with meaty aromas, while HSS contributed to sulfur-like off-flavors. Principal component analysis showed that the LTPS samples had shorter distances across various storage periods compared to HSS, indicating reduced differences in aroma difference. The findings of this study demonstrate LTPS’s dual efficacy in microbial control and aroma preservation. The technology presents a viable strategy for extending the shelf life of pre-prepared meat dishes while reducing oxidative and flavor deterioration, thereby establishing a solid foundation for LTPS application in the pre-prepared food sector. Full article

Background/Objectives: Microcolins A–M are cytotoxic marine lipopeptides produced by the cyanobacterium Moorena producens, also known as Lyngbya majuscula. Recent studies have shown that two compounds in the series, microcolins B and H, can form covalent complexes with phosphatidylinositol transfer proteins α and β (PITPα/β) upon the reaction of their α,β-unsaturated ketone group with the thiol group of a key cysteine residue of PITP. These observations prompted us to compare the binding of all microcolins and a few related derivatives (VT01454 and (deoxy)majusculamide D) to PITP to delineate structure–binding relationships. Methods: A molecular docking analysis led to the identification of microcolin E as the potentially best PITPα binder in the series, followed by microcolins B and H and analog VT01454. The computational data agree well with the published experimental results. Results: The binding of microcolin H into a large cavity of PITPα positions its reactive electrophilic α,β-unsaturated ketone close to the thiol of Cys95, enabling the facile formation of a covalent C-S linkage. A similar bonding can occur with the Cys94 of PITPβ. Molecular models of microcolins bound to PITP were compared to identify structural elements chiefly implicated in the recognition process. Conclusions: This computational study provides guidance in the design of microcolin derivatives targeting PITPα/β considered targets for cancer and inflammatory pathologies. Full article