Search Results (308)

The efficient recovery of rhenium (Re), a critical metal in high-tech industries, is essential to address its growing demand and reduce reliance on primary mining. In this study, we developed novel anion-exchange resins for the selective adsorption and recovery of Re(VII) ions from acidic solutions, simulating industrial by-products. The resins were synthesized from a vinylbenzyl chloride-co-divinylbenzene copolymer modified with aliphatic, heterocyclic, and aromatic weakly basic amines, selected from among bis(3-aminopropyl)amine (BAPA), 1-(2-pyrimidinyl)piperazine (PIP), thiosemicarbazide (TSC), 2-amino-3-hydroxypyridine (AHP), 1-(2-hydroxyethyl)piperazine (HEP), 4-amino-2,6-dihydroxypyrimidine (AHPI), and 2-thiazolamine (TA). The adsorption of Re on BAPA, PIP, and HEP resins obeyed the Langmuir model, and the resins exhibited high adsorption capacities, with maximum values reaching 435.4 mg Re g⁻¹ at pH 6. Furthermore, strong selectivity for ReO₄⁻ ions over competing species, including Mo, Cu, and V, was noted in solutions simulating the leachates of the by-products of Cu-Mo ores. Additionally, complete elution of Re was possible. The developed resins turned out to be highly suitable for the continuous-flow-mode adsorption of ReO₄⁻, revealing outstanding adsorption capacities before reaching column breakthrough. In this context, the novel anion-exchange resins developed offer a reference for further Re recovery strategies. Full article

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

Heterocycles—cyclic compounds containing at least one non-carbon heteroatom (e.g., N, O, S)—are fundamental in medicinal chemistry due to their influence on a drug’s physicochemical and biological properties. They improve solubility, bioavailability, and facilitate molecular recognition through their electronic and hydrogen-bonding features. These properties make them indispensable in drug design. This study focuses on the synthesis of a key heterocyclic intermediate: benzyl-N-[4-(2-hydroxyethyl)-1,3-thiazol-2-yl]carbamate. This molecule incorporates a thiazole ring, known for its rigidity and electronic properties, that enhances target interactions. The 2-position bears a Cbz-protected amine, enabling orthogonal deprotection, while the 4-position features a hydroxyethyl side chain, providing a handle for further chemical modifications via nucleophilic substitution. Herein, we report the successful synthesis of this intermediate along with its full ¹H and ¹³C NMR spectra, melting point, and crystal structure, confirming its identity and purity. Full article

Monoterpenes and their derivatives are important starting compounds in the design of new biologically active substances. In particular, cineole, isolated from eucalyptus essential oil, exhibits a wide range of biological activities. Here, the synthesis of new heterocyclic compounds containing a cineole fragment by the acid-catalyzed condensation of α-pinene-derived 8-hydroxy-6-hydroxymethyllimonene with monoterpene aldehydes was carried out for the first time. The reactions of 8-hydroxy-6-hydroxymethyllimonene with cuminaldehyde, perillylaldehyde, myrtenal, citral, and geranial were studied in the presence of heterogeneous K10 clay or Lewis acid BF₃·Et₂O. The main products of these reactions were compounds with the methanopyrano[4,3-b]pyran scaffold having a 1,8-cineole fragment. As a result of this work, five new compounds with the methanopyrano[4,3-b]pyran scaffold were synthesized. The use of BF₃·Et₂O led to an increase in the yields of target products, compared with the results obtained on K10 clay. Full article

Two hydrazone Schiff base-bridging ligands with different heterocycles {2-[(E)-(5-chloro-2-hydroxyphenyl)methylidene]diazanyl}(pyrazine-2-yl)methanone (H₂L_Schiff-1) and (E)-N′-(2-hydroxy-3-methoxybenzylidene)nicotinohydrazide (H₂L_Schiff-2) together with 1,3-di(2-pyridyl)-1,3-propanedione (Hdpp) were chosen to construct two new Dy₂ complexes, [Dy₂(L_Schiff-1)₂(DMF)₂(dpp)₂]·0.5DMF (1) and [Dy₂(L_Schiff-2)₂(DMF)₂(dpp)₂]·2DMF (2). Although the [N₂O₆] coordination spheres are observed for the Dy³⁺ ions in 1 and 2, their coordination configurations have some differences (both the biaugmented trigonal prism and the Snub diphenoid J84 in 1 and only the biaugmented trigonal prism in 2). Magnetic research revealed that both 1 and 2 possess ferromagnetic interactions between two Dy³⁺ ions and perform as zero-field single-molecule magnets, with U_eff/k values of 49.7 K at 0 Oe for 1 and 151.8 K at 0 Oe for 2. This work suggests that the heterocycle groups (pyrazine vs. pyridine) on the hydrazone Schiff base-bridging ligands have effects on the SMM properties of 1 and 2. Full article

In this study, a C-C bond-linked triazole-fused oxadiazole energetic compound, 4-amino-5-(4-amino-1,2,5-oxadiazol-3-yl)-2,4-dihydro-3H-1,2,4-triazol-3-one (1), was successfully designed and efficiently synthesized. Following nitration, a functional group-modified nitramine energetic compound (2) was obtained, and its energetic ionic salt (3) was further prepared. A comprehensive characterization of the structures of these three compounds was conducted, resulting in the successful elucidation of the single-crystal structures of compound 2·Ca²⁺·6H₂O and compound 3·MeOH. Compound 2 exhibited a positive formation enthalpy (56.2 kJ·mol⁻¹) and moderate mechanical sensitivity (FS = 120 N, IS = 12 J). Due to the presence of the nitramine group, compound 2 exhibited a relatively low thermal decomposition temperature (T_dec = 94 °C). However, the thermal stability of compound 3 was significantly improved (T_dec = 233 °C), which is attributed to salt formation. Compound 3 exhibits a positive formation enthalpy (121.0 kJ·mol⁻¹), along with excellent detonation performance (D = 8120 m·s⁻¹, P = 32.1 GPa) and reduced mechanical sensitivity (FS = 224 N, IS = 24 J). Therefore, the multi-heterocyclic compound, joined via C-C bond linkage, demonstrates outstanding performance, offering a new avenue for the design and synthesis of energetic materials. Full article

The interaction of cobalt(II) with first-generation quinolones oxolinic acid (Hoxo), flumequine (Hflmq), pipemidic acid (Hppa) and cinoxacin (Hcx) in the presence of the N,N′-donor heterocyclic ligands 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen) afforded a series of novel cobalt complexes, namely [Co(bipy)₂(oxo)](PF₆)₂·H₂O (1), [Co(phen)₂(oxo)](PF₆)₂·0.5CH₃OH·0.5H₂O (2), [Co(bipy)₂(flmq)](PF₆)₂·0.5CH₃OH·0.5H₂O (3), [Co(bipy)₂(ppa)](PF₆)₂·CH₃OH·0.5H₂O (4), [Co(phen)₂(cx)](PF₆)₂·CH₃OH·0.5H₂O (5), and [Co(phen)₂(flmq)](PF₆)·0.5CH₃OH·H₂O (6). The characterization of the complexes involved physicochemical techniques, various spectroscopies and single-crystal X-ray crystallography. The affinity of complexes to calf-thymus (CT) DNA was monitored with various techniques, suggesting intercalation in-between the DNA-nucleobases as the most probable interaction mode, which may be combined with electrostatic interactions as a result of the cationic nature of the complexes. The affinity of the complexes for bovine and human serum albumin proteins was monitored, and the determined corresponding albumin-binding constants revealed a tight and reversible interaction. Full article

Ion interactions with molecular structures give insights into physicochemical processes in the cosmos, radiation damage, plasma, combustion, and biomass conversion reactions. At the atomic scale, these interactions lead to excitation, ionization, and dissociation of the molecular components of structures found across all these environments. Furan, cyclic aromatic ether (C₄H₄O), serves as a gas-phase deoxyribose analog and is crucial for understanding key pathways in renewable biomass conversion, as its derivatives are versatile molecules from lignocellulosic biomass degradation. Therefore, collisions of H₃⁺ and C⁺ ions with gas-phase furan molecules were investigated in the 50–1000 eV energy range, exploiting collision-induced emission spectroscopy. High-resolution fragmentation spectra measured at 1000 eV for both cations reveal similar structures, with C⁺ collisions resulting in more significant furan fragmentation. Relative cross-sections for product formation were measured for H₃⁺ + C₄H₄O collisions. Possible collisional processes and fragmentation pathways in furan are discussed. These results are compared with those for tetrahydrofuran and pyridine to illustrate how the type and charge of the projectile influence neutral fragmentation in heterocyclic molecules. Full article

Recently, research and development in the field of dye-sensitized solar cells has been actively advanced, as the technology constitutes a potential alternative to silicon-based photovoltaic devices. Modification of the molecular structure of the dye can enhance the adsorption on the TiO₂ surface, improve the light absorption capacity, suppress the charge recombination, increase the electron injection rate, and thereby improve the overall performance of the solar cell. Carbazole and phenothiazine are rigid heterocyclic compounds containing nitrogen as a heteroatom with large π-conjugated skeletons. Phenothiazine differs from carbazole by the presence of sulfur as an additional electron-rich heteroatom. The inclusion of this heteroatom in the structure of the compounds can indeed improve the electron-donating properties, affect the conjugation, and thus affect the optical, electronic, and electrochemical properties of the chromophores as a whole. The difference in planarity when comparing carbazole with phenothiazine can be useful from several points of view. The planar structure of carbazole increases the degree of conjugation and the electron transfer capacity, which can increase the photocurrent of the cell. The nonplanar structure of phenothiazine helps to prevent π-stacking aggregation. This review comprehensively summarizes the progress in the field of synthesis of organic dyes for solar cells with an emphasis on the comparative analysis of two electron-donating moieties, carbazole and phenothiazine. In addition, the review describes in detail the relationship between the structure of the compounds (dyes), their properties, and the performance of solar cells. Full article

N-Heterocyclic carbenes (NHCs) have been widely utilized over the past three decades due to their broad applications, yet synthetic methods for their preparation remain limited. A promising approach for NHC generation involves the thermolysis of NHC adducts. Herein, we report the synthesis of NHC pentafluorobenzene adducts featuring an o-carboranyl group in the backbone (2), which, unlike previously studied systems, resists thermal decomposition. Density functional theory (DFT) calculations were used to investigate the discrepancy, revealing that the decomposition reaction is kinetically controlled. For widely studied NHC systems like IMes and SIMes, the activation barriers were calculated to be 246.3 kJ/mol and 267.3 kJ/mol, respectively, aligning with reactions requiring heating. In contrast, the o-carborane system exhibited a significantly higher barrier of 320.5 kJ/mol, primarily due to the structural influence of the o-carborane backbone. Further analysis indicates that delocalization of π-electrons from the backbone into the NHC’s p-orbitals lowers the activation barrier, whereas delocalization into an exo-NHC ring increases it. These findings provide new insights into the thermal generation of NHCs and we hope it can offer guidance for future NHC design and synthesis. Full article

The search for new heterocyclic compounds with biological potential is one of the current challenges in modern chemistry. Therefore, the comprehensive study of (3 + 2) cycloaddition (32CA) reactions between a series of aryl-substituted nitrile N-oxides (NOs) and (E)-3,3,3-tribromo-1-nitroprop-1-ene (TBNP) is carried out. According to the experimental research, in all tested 32CAs, the proper (4RS,5RS)-3-aryl-4-nitro-5-tribromomethyl-2-isoxazolines are obtained as only one reaction product. In turn, the quantum–chemical MEDT study shows that the creation of heterocycles occur via the polar attack of zwitterionic moderate-nucleophilic NOs to strong electrophilic TBNP. The reactions are realized according to a two-stage, one-step asynchronous mechanism, in which the formation of the O-C(CBr₃) bond takes place once the C-C(NO₂) bond is already formed. What is more, the computational analysis confirmed the experimental results. At the end, the obtained 2-isoxazolines were docked to three proteins: gelatinase B, cyclooxygenase COX-1, and Caspase-7. We hope that the presented study will be helpful for searching for the future direction of application for this class of organic compounds. Full article

N,O-donor hybrid heterocyclic extractants have great potential for separation of actinides from lanthanides in spent nuclear fuel reprocessing processes. We demonstrate that this type of reagents can be used for primary concentration of actinides contained in eudialyte, a promising mineral containing a heavy group of lanthanides. With respect to lanthanide ions, the efficiency of their extraction decreases in the series L3 >> L1 > L2, and the extraction of actinides decreases in the series L1 ≈ L3 >> L2. For the extractant L2 based on 2,2′-bipyridine-6,6′-dicarboxylic acid diamide, the efficiency of lanthanide purification from U, Th exceeds 50. The structure and stereochemical features of the ligands do not have a significant effect on the composition of the formed complexes. The solvation numbers are close to 1 for all range f-elements studied, except for thorium, which indicates the predominant formation of complexes with the composition ratio of 1:1. The solvation numbers 1.4–1.5 are observed for thorium(IV), and the established values indicate the formation of a mixture of complexes with the composition ratios of 1:1 and 2:1. Full article

In this study, we examined the oxidation of (E)-2-hydroxy-1-naphthaldehyde oxime with lead tetraacetate in tetrahydrofuran that produced novel (E)-7a,8,9,10-tetrahydro-12H-naphtho[1,2-e]pyrrolo[2,1-b][1,3]oxazin-12-one oxime and 1-(pyrrolidin-1-yl)naphtho[1,2-d]isoxazole and known 7a,8,9,10-tetrahydro-12H-naphtho[1,2-e]pyrrolo-[2,1-b][1,3]oxazin-12-one in 15, 18, and 10% yields, respectively. The oxime is partially hydrolyzed to its corresponding ketone. Modifying the oxidants and reaction conditions did not improve the product yields. Based on previous studies in our laboratory, we proposed that the reactions proceed via the formation of an o-naphthoquinone nitrosomethide intermediate; 1D and 2D NMR, HRMS, IR, and UV-VIS spectra provided information that supported the structure of the products. Full article

Heterocyclic aromatic amines (HAAs), known for their mutagenic and carcinogenic potential, are formed during the heating of protein-rich food items. Detecting HAAs swiftly and accurately poses challenges due to complex food matrices and low HAA concentrations. In this study, a simple and efficient magnetic solid-phase extraction (MSPE) strategy was developed for the simultaneous isolation and enrichment of three HAAs such as 2-amino-3,4,8-trimethylimidazo [4,5-f]quinoxaline (4,8-DiMeIQx), 2-amino-3,8-dimethylimidazo [4,5-f]quinoxaline (MeIQx), and 2-amino-3-methylimidazo [4,5-f]quinoline (IQ) in processed meats, employing the magnetic covalent organic framework Fe₃O₄@MOF-545-AMSA as an adsorbent. It was synthesized via a solvothermal method, with Fe₃O₄ as the magnetic core. Its building blocks are as follows: zirconium (Zr) as the coordination metal ion, tetrakis(4-carboxyphenyl)porphyrin and benzoic acid as organic ligands, and aminomethanesulfonic acid (AMSA). This composite captures targeted HAAs efficiently by exploiting the unique porous MOF-545-AMSA structure, specific metal–ligand coordination, and AMSA’s amino and sulfonic acid groups. The quantification of HAAs was achieved through the combination of Ultra-Performance Liquid Chromatography–Tandem Mass Spectrometry (UPLC-MS/MS) and MSPE, demonstrating satisfactory linearity (R² ≥ 0.9917), high recovery rates (83.7–111.0%), and low detection limits (0.1–1.0 μg/kg). Moreover, an automated high-throughput detection system was developed using MSPE to assess the presence of HAAs in meat products. Full article

Polystyrene-supported chiral hydroxyamide-functionalized benzimidazolium chloride was synthesized by reacting Merrifield resin with a substituted-azole derived from (S)-leucinol. The combination of [IrCl(cod)]₂ and the resulting polymer-supported N-heterocyclic carbene (NHC) ligand precursor catalyzed the enantioselective reduction of ketones using (EtO)₂MeSiH under heterogeneous reaction conditions via a pre-mixing reaction procedure. Additionally, the solid-state resin could be easily recovered through simple filtration and the catalyst system’s reusability was evaluated. Full article