Search Results (139)

Copper(II) complexes with 2,2′:6′,2″-terpyridines (terpys) are promising candidates for anticancer therapy and catalysis. Their structural and optical properties can be tuned by modifying the terpy backbone, including a substitution at the 4′ position or the replacement of peripheral pyridines with thiazole rings, forming 2,6-bis(thiazol-2-yl)pyridines (dtpys). dtpy-based copper(II) complexes (Cu-dtpys), despite their applicative potential, are barely characterized in the literature. Here, the series of Cu-dtpys (1–13) was synthesised and characterized by FT-IR, HRMS, X-ray diffraction, and UV-Vis spectroscopy. Their structural and optical features were compared to previously studied Cu-dtpys (14–24) and their terpy analogues (Cu-terpy-1 ÷ Cu-terpy-24). The detailed analysis revealed that five-coordinate Cu-dtpys complexes adopt a square pyramidal geometry comparable to that of Cu-terpys complexes but with markedly smaller deviations from the ideal square pyramid. Compared with Cu-terpys, Cu–Cl_apical bonds are shorter, while Cu–N_central bonds are elongated. The Cu-dtpy systems usually present the longest wavelength of the lowest energy absorption band in comparison to Cuterpys. The analysis of the relationship between Hammett’s constant and wavelength of absorption indicates that the most promising from the photophysical point of view are compounds 4–6, 10–13, 16–17, and 22, for which a newly formed intraligand charge transfer band is formed. Full article

In this study, the transformation of 2,5-furandicarboxylic acid (FDCA) to 2,5-bis(aminomethyl)furan (BAMF) is proposed and investigated for the first time. Using FDCA as the substrate, the process involves two key steps: first, converting FDCA to 2,5-dicyanofuran (DCF) via carboxy-cyanation, followed by the heterogeneous catalytic hydrogenation of DCF to produce BAMF. For the carboxy-cyanation, two ammoniation routes were compared, including the molten ammoniated dehydration route and the moderate ammoniated dehydration route. The difference between the ammoniation of bio-based cyclic dicarboxylic acid and that of petroleum-based aliphatic dicarboxylic acid was discovered. A moderate ammoniated dehydration route that is more suitable for bio-based cyclic dicarboxylic acid has been developed. SOCl₂ was found to effectively activate the stable carboxyl group and act as a dehydrating agent, facilitating the dehydration of the intermediate 2,5-furandicarboxamide (FDAM) to DCF with higher efficiency. For the hydrogenation reaction of DCF, Raney Co exhibited excellent catalytic performance, achieving a 94.5% yield of BAMF from DCF. Based on industrial practice, this research represents the first exploration of the pathway from bio-based FDCA to BAMF, which opens a new line for the sustainable production of bio-based diamines. Full article

Tungstophosphoric acid (TPA) has been supported on mesoporous silicas prepared using urea as the pore forming agent. The amount of urea (20, 30, or 40% w/w) influences the silica specific surface area (S_BET), total pore volume (Vp), and average pore diameter (Dp). The materials synthetized using 20% w/w (SiU20) display mainly mesoporous structures, with the highest Vp and Dp values being chosen to be used as TPA support. The SiU20-TPA solids with different TPA loadings (10, 20, or 30% w/w) have been used as supports for chiral copper catalysts with bis(oxazoline) or azabis(oxazoline) ligands. The catalytic efficiency of enantioselective cyclopropanation strongly depends on support morphology and TPA loading. SiU-TPA20 has been shown to be the optimal one. The stability of the complex is also a very important parameter, and the best results are obtained with an excess of chiral ligand to ensure the correct formation of the complex on the solid. In this way, with azabox-Cu/SiU20-TPA20 it is possible to obtain a highly selective (90% ee for the trans-cyclopropanes) and recoverable catalyst. Full article

Ribulose bisphosphate carboxylase (RuBisCO) is the primary regulator of carbon fixation in the plant kingdom. Although the large subunit (RBCL) is the site of catalysis, RuBisCO efficiency is also influenced by the sequence divergence of the small subunit (RBCS). This project compared the RBCS gene family in C3 and C4 grasses to identify genetic targets for improved crop photosynthesis. Triticeae/Aveneae phylogeny groups exhibited a syntenic tandem duplication array averaging 326.1 Kbp on ancestral chromosomes 2 and 3, with additional copies on other chromosomes. Promoter analysis revealed a paired I-box element promoter arrangement in chromosome 5 RBCS of H. vulgare, S. cereale, and A. tauschii. The I-box pair was associated with significantly enhanced expression, suggesting functional adaptation of specific RBCS gene copies in Triticaeae. H. vulgare-derived pan-transcriptome data showed that RBCS expression was 50.32% and 28.44% higher in winter-type accessions compared to spring types for coleoptile (p < 0.05) and shoot, respectively (p < 0.01). Molecular dynamics simulations of a mutant H. vulgare Rubisco carrying a C4-like amino acid substitution (G59C) in RBCS significantly enhanced the stability of the Rubisco complex. Given the known structural efficiency of C4 Rubisco complexes, G59C could serve as an engineering target for enhanced RBCS in economically crucial crop species which, in comparison, possess less efficient Rubisco complexes. Full article

This work is devoted to the study of the effect of small Bi additives on the functional properties of Pdx:Bi/Al₂O₃ catalysts in the selective oxidation of glucose to gluconic acid. The catalysts obtained by the joint impregnation method were characterized (TEM) by high dispersion of bimetallic nanoparticles with a median diameter of 4–5 nm. The structure of the Pd-Bi solid solution was confirmed via XPS and showed a change in the valence state of Pd and Bi depending on the Bi content, as well as the fraction of the oxidized state of Bi. TPR-H₂ revealed various forms of Pd, including PdO and mixed Pd-O-Bi structures. The Pd10:Bi1/Al₂O₃ catalyst demonstrated the highest efficiency (77.2% glucose conversion, 96% sodium gluconate selectivity), which is due to the optimal ratio between Pd and Bi, ensuring the stabilization of metallic Pd and preventing its oxidation. Full article

A new complex, tetrakis(1,10-phenanthroline)-bis(succinate)-(µ₂-oxo)-bis(iron(III)) nonahydrate, [Fe₂(Phen)₄(Succinate)₂(μ-O)](H₂O)₉, was synthesized using the slow evaporation method. This study provides a comprehensive characterization of this coordination compound, focusing on its structural, spectroscopic, and thermal properties, which are relevant for applications in catalysis, material science, and chemical engineering processes. Single-crystal X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared (FT-IR), ultraviolet-visible (UV-Vis) spectroscopy, and thermoanalytical analyses were employed to investigate the material properties. Intermolecular interactions were further explored through Hirshfeld surface analysis. XRD results revealed a monoclinic crystal system with the C2/c space group, lattice parameters: a = 12.7772(10) Å, b = 23.0786(15) Å, c = 18.9982(13) Å, β = 93.047(2)°, V = 5594.27(7) ų, and four formulas per unit cell (Z = 4). The crystal packing is stabilized by C–H⋯O, C–O⋯H, C–H⋯π, and π⋯π intermolecular interactions, as confirmed by vibrational spectroscopy. The heteroleptic coordination environment, combining weak- and strong-field ligands, results in a low-spin state with an estimated crystal field stabilization energy of −4.73 eV. Electronic properties indicate direct allowed transitions (γ = 2) with a maximum optical band gap of 2.66 eV, suggesting potential applications in optoelectronics and photochemical processes. Thermal analysis demonstrated good stability within the 25–136 °C range, with three main stages of thermal decomposition, highlighting its potential for use in high-temperature processes. These findings contribute to the understanding of Fe(III)-based complexes and their prospects in advanced material design, catalytic systems, and process optimization. Full article

The urgent need for sustainable CO₂ conversion technologies has driven the development of advanced photocatalysts that harness solar energy. This study employs a CTAB-assisted solvothermal method to fabricate a Z-scheme heterojunction Fe-MOFs/V_O-Bi₂WO₆ (FM/V_O-BWO) for photocatalytic CO₂ reduction. Positron annihilation lifetime spectroscopy (PALS) was employed to confirm the existence of oxygen vacancies, while spherical aberration-corrected transmission electron microscope (STEM) characterization verified the successful construction of heterointerfaces. X-ray absorption fine structure (XAFS) spectra confirmed that the defect configuration and heterostructure changed the surface chemical valence state. The optimized 1.0FM/V_O-BWO composite demonstrated exceptional photocatalytic performance, achieving CO and CH₄ yields of 60.48 and 4.3 μmol/g, respectively, under visible-light 11.8- and 1.5-fold enhancements over pristine Bi₂WO₆. The enhanced performance is attributed to oxygen vacancy-induced active sites facilitating CO₂ adsorption/activation. In situ molecular spectroscopy confirmed the formation of critical CO₂-derived intermediates (COOH* and CHO*) through surface interactions involving four-coordinated and two-coordinated hydrogen-bonded water molecules. Furthermore, the accelerated interfacial charge transfer efficiency mediated by the Z-scheme heterojunction has been conclusively demonstrated. This work establishes a paradigm for defect-mediated heterojunction design, offering a sustainable route for solar fuel production. Full article

It is known that the presence of redox-inactive metals in the active center of an enzyme has a significant effect on its activity. In this regard and for other reasons, the effect of redox-inactive metals on redox processes, such as electron transfer, oxygen and hydrogen atom transfer, as well as the breaking and formation of O–O bonds in reactions catalyzed by transition metals, has been widely studied. Many questions about the role of redox-inactive metals in the mechanisms of these reactions remain open. In this paper, the mechanism of catalysis by bi- and triple hetero-binuclear heteroligand complexes including Ni and redox-inactive alkali metals ((A) {Ni(acac)₂∙L²} and (B) {Ni(acac)₂∙L²∙PhOH} (L² = MSt (M = Li, Na, or K)) in the process of the selective oxidation of ethylbenzene by molecular oxygen into α-phenyl ethyl hydroperoxide is considered. The activity of A and B complexes towards O₂, ROOH, and RO₂^• radicals was studied. Based on kinetic data, we suggest that the high catalytic efficiency of B triple complexes in oxidation processes may be associated with the role of outer-sphere regulatory interactions, with the formation of stable supramolecular structures due to intermolecular H bonds. This assumption was confirmed using the AFM method. Prospects for studying catalysis by complexes ({Ni(acac)₂∙L²} and {Ni(acac)₂∙L²∙PhOH}) that are models of NiARD (Ni-Acyreductone dioxygenase) are discussed. Full article

Emerging pollutants, such as N-acetyl-para-aminophenol, pose significant challenges to environmental sustainability, and Bi₂Fe₂O₂ (BFO) nanomaterials are an emerging class of piezoelectric materials. This study presents a novel piezoelectric-driven Fenton system based on Bi₂Fe₄O₉ nanosheets for the efficient degradation of organic pollutants. BFO nanosheets with varying thicknesses were synthesized, and their piezoelectric properties were confirmed through piezoresponse force microscopy and heavy metal ion reduction experiments. The piezoelectric electrons generated within the BFO nanosheets facilitate the in situ production of hydrogen peroxide, which in turn drives the Fenton-like reaction. Furthermore, the piezoelectric electrons enhance the redox cycling of iron in the Fenton process, boosting the overall catalytic efficiency. The energy band structure of BFO nanosheets is well-suited for this process, enabling efficient hydrogen peroxide generation and promoting Fe³⁺ reduction. The findings demonstrate that thinner BFO nanosheets exhibit superior piezoelectric activity, leading to enhanced catalytic performance. Additionally, the incorporation of gold nanodots onto BFO nanosheets further boosts their piezocatalytic efficiency, particularly in the reduction of Cr (VI). The system exhibited robust oxidative capacity, stability, and recyclability, with reactive oxygen species (ROS) verified via electron paramagnetic resonance spectroscopy. Overall, BFO nanosheets, with their optimal energy band structure, self-supplied hydrogen peroxide, and enhanced Fe³⁺ reduction, represent a promising, sustainable solution for advanced oxidation processes in wastewater treatment and other applications. Full article

1,2-Diphenylethylenediamine (DPEDA) is a privileged chiral scaffold being used in the construction of a broad variety of organocatalysts and ligands for enantioselective organic reactions. This molecule gave a significant contribution in the synthesis of structurally different bi/multifunctional organocatalysts. DPEDA played an essential role in the development of organocatalysts capable of yielding important information on the different reaction mechanisms, like enamine, iminium, hydrogen-bonding and anion-binding catalysis. The aim of the present review is to highlight and summarize the achievements reached in the last 20 years (2004–2024) in the chemistry of DPEDA-based organocatalysts for asymmetric synthesis. Full article

The coupling between bis(2-oxazolines) and two equivalents of aromatic aldehydes in the presence of catalytic amounts of NiCl₂ affords an ester-imine product in synthetically useful yields. This virtually unknown, 100% atom-economic transformation involves the formal metathesis between the C=N double bond of the bis(2-oxazoline) moiety, which undergoes ring-opening, and the C=O double bond of the aldehyde. The scope of this transformation is studied, and a mechanism is proposed based on DFT calculations. Full article

To enhance the ignition and combustion characteristics of boron (B), in this study, a suitable, energetic fluorinated group (NF₂) that can improve energy and promote combustion efficiency was utilized and B/NF₂ composites (B/PDB) with three different particle sizes (10–20 μm, <5 μm, and 0.5–2 μm) were prepared through energetic fluorinated surface modifications with a PDB layer, a copolymer of difluoroaminomethyl-3-methylethoxybutane and 3,3′-bis(azidomethyl)oxetane, coated on the surface of B. The morphology and structure of B/PDB were characterized via the FTIR, SEM, TEM, and XPS techniques. The results indicate that all B/PDB particle sizes were successfully coated by NF₂ on the surfaces of B particles through the PDB layer. The TG curves in the thermal analyses were used to determine the amount of the PDB layer of B/PDB with different particle sizes. Based on the DSC curves, NF₂ of composites with better catalysis during ammonium perchlorate (AP) decomposition. Additionally, the effects of NF₂ on both B/PDB and B/PDB with AP were investigated through PY-GC/MS, ignition, and combustion. Compared with pure B, NF₂ significantly improved the thermal conductivity, thereby decreasing the ignition delay of B/PDB, and the ignition delay of B/PDB with AP. The combustion of B/PDB and AP was more intense, extending the combustion duration, forming volatile fluorine compounds, and increasing combustion reaction efficiency. In general, this energetic fluorinated-centred surface modification has potential applications to enhance the ignition and combustion characteristics in B. Full article

Bis-triazoles separated by a symmetrical linking group are joined at C4 of each triazole or at N1 of each triazole. Preparation of a series of bis-1H-1,2,3-triazoles derived from o-bis(azidomethyl)benzene and an alkyne is reported with use of copper N-heterocyclic carbene catalysis with microwave-assisted heating in an aqueous solvent. The products were symmetrical N1–N1′-bis-1H-1,2,3-triazoles. Additional syntheses utilized dialkynes and organic azides to prepare symmetrical C4–C4′-bis-1H-1,2,3-triazoles. Pure products were often obtained directly when water was used as the solvent with microwave-assisted heating. Results are given for experiments using conventional heating or no heating. Sonication results are given for a reaction where microwave-assisted heating was unsatisfactory. Full article

Recently, prokaryotic laccases from lactic acid bacteria (LAB), which can degrade biogenic amines, were discovered. A laccase enzyme has been cloned from Oenococcus oeni, a very important LAB in winemaking, and it has been expressed in Escherichia coli. This enzyme has similar characteristics to those previously isolated from LAB as the ability to oxidize canonical substrates such as 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,6-dimethoxyphenol (2,6-DMP), and potassium ferrocyanide K₄[Fe(CN₆)], and non-conventional substrates as biogenic amines. However, it presents some distinctiveness, the most characteristic being its psychrophilic behaviour, not seen before among these enzymes. Psychrophilic enzymes capable of efficient catalysis at low temperatures are of great interest due to their potential applications in various biotechnological processes. In this study, we report the discovery and characterization of a new psychrophilic laccase, a multicopper oxidase (MCO), from the bacterium Oenococcus oeni. The psychrophilic laccase gene, designated as LcOe 229, was identified through the genomic analysis of O. oeni, a Gram-positive bacterium commonly found in wine fermentation. The gene was successfully cloned and heterologously expressed in Escherichia coli, and the recombinant enzyme was purified to homogeneity. Biochemical characterization of the psychrophilic laccase revealed its optimal activity at low temperatures, with a peak at 10 °C. To our knowledge, this is the lowest optimum temperature described so far for laccases. Furthermore, the psychrophilic laccase demonstrated remarkable stability and activity at low pH (optimum pH 2.5 for ABTS), suggesting its potential for diverse biotechnological applications. The kinetic properties of LcOe 229 were determined, revealing a high catalytic efficiency (kcat/Km) for several substrates at low temperatures. This exceptional cold adaptation of LcOe 229 indicates its potential as a biocatalyst in cold environments or applications requiring low-temperature processes. The crystal structure of the psychrophilic laccase was determined using X-ray crystallography demonstrating structural features similar to other LAB laccases, such as an extended N-terminal and an extended C-terminal end, with the latter containing a disulphide bond. Also, the structure shows two Met residues at the entrance of the T1Cu site, common in LAB laccases, which we suggest could be involved in substrate binding, thus expanding the substrate-binding pocket for laccases. A structural comparison of LcOe 229 with Antarctic laccases has not revealed specific features assigned to cold-active laccases versus mesophilic. Thus, further investigation of this psychrophilic laccase and its engineering could lead to enhanced cold-active enzymes with improved properties for future biotechnological applications. Overall, the discovery of this novel psychrophilic laccase from O. oeni expands our understanding of cold-adapted enzymes and presents new opportunities for their industrial applications in cold environments. Full article

Semiconductor hollow spheres have garnered significant attention in recent years due to their unique structural properties and enhanced surface area, which are advantageous for various applications in catalysis, energy storage, and sensing. The present study explores the surfactant-assisted synthesis of bismuth ferrite (BiFeO₃) hollow spheres, emphasizing their enhanced visible-light photocatalytic activity. Utilizing a novel, facile, two-step evaporation-induced self-assembly (EISA) approach, monodisperse BiFeO₃ hollow spheres were synthesized with a narrow particle size distribution. The synthesis involved Bi/Fe citrate complexes as precursors and the triblock copolymer Pluronic P123 as a soft template. The BiFeO₃ hollow spheres demonstrated outstanding photocatalytic performance in degrading the emerging pollutants Rhodamine B and metronidazole under visible-light irradiation (100% degradation of Rhodamine B in <140 min and of metronidazole in 240 min). The active species in the photocatalytic process were identified through trapping experiments, providing crucial insights into the mechanisms and efficiency of semiconductor hollow spheres. The findings suggest that the unique structural features of BiFeO₃ hollow spheres, combined with their excellent optical properties, make them promising candidates for photocatalytic applications. Full article