Acta Chimica Slovenica最新文献

A new heterocyclic Schiff base, 4-(1-(4-(dimethylamino)benzyl)-5-methyl-1H-benzo[d]imidazol-2-yl)-N, N-dimethylaniline (L), has been synthesized and characterized. The molecular structure of compound L was confirmed by 1H NMR, FT-IR, UV-Vis and elemental analysis. The performance and inhibition mechanism of compound L against the corrosion of carbon steel in 1 M HCl and 0.5 M H2SO4 were studied by weight loss method, Tafel polarisation and electrochemical impedance spectroscopy (EIS). The compound behaves as a mixed-type inhibitor and obeys the Langmuir adsorption isotherm. The morphological appearance of compound L on the carbon steel surface by scanning electron microscopy (SEM) and atomic force microscopy (AFM) confirmed that compound L was adsorbed on the carbon steel to form a film. The thermodynamic parameters were calculated and discussed. Quantum chemical parameters were also determined. This study confirms the agreement between the experimental and theoretical results.

A series of new aminomethylpyridinium hexafluoridosilicate salts with the formula (RH)2[SiF6] (where R = 2-amino-3-methylpyridine (1), 2-amino-4-methylpyridine (2), 2-amino-5-methylpyridine (3) and 2-amino-6-methylpyridine (4)) were prepared by the reaction of various methyl-substituted 2-aminopyridines with hydrogen fluoride solution of silica. The crystal packing of these ionic salts is compared with respect to the position of the methyl group on the aromatic ring. The crystal structures are dominated by the non-covalent interactions: the N-H···F hydrogen bonds and π-π interactions between aromatic rings. The potential of the corresponding ionic salts to enable supramolecular associations was investigated. Compounds 1-4 were also characterized by 1H, 19F NMR and IR spectroscopy.

The chemical evolution of amino acids, especially sulfur-containing ones, requires appropriate conditions and natural sources to provide starting prebiotic compounds. In the present study hydrothermal vents, volcanoes and oceans were chosen as a plausible environment, where prebiotic reactions take place. The suggested reaction network starts only with three compounds - water, hydrogen cyanide/formamide and hydrogen sulfide. The present study suggests one-pot hydrothermal experiment in laboratory conditions to demonstrate some vital prebiotic precursors formation. The reaction pathways from starting molecules to amino acids were modelled at SCS-MP2/cc-pVDZ/SMD level of the theory. The calculated energetic characteristics facilitate the determination of the plausible reaction pathways for amino acids - glycine, serine and alanine, along with sulfur-containing ones - cysteine and homocysteine under hydrothermal scenario.

In this study, a simple, and eco-friendly high-performance liquid chromatography-diode array detection (HPLC-DAD) method was developed and validated for analyzing methylxanthines, including theobromine (TB), theophylline (TF), and caffeine (CF). This method demonstrated excellent performance using a mobile phase of water and ethanol in a core-shell Kinetex® C18 column. The method was linear (1-100 µg mL-1), exhibiting high precision and accuracy with relative standard deviations below 2.67% and recoveries ranging from 98.17% to 108.23%. The detection and quantification limits ranged from 0.19-0.26 µg mL-1 and 0.64-0.87 µg mL-1, respectively. We applied this method to analyze powdered lemon-flavored beverages enriched with black or green tea extracts. CF was detected exceeding 1.62 g kg-1. The proposed method showed excellent greenness, evidenced by the Analytical Eco-Scale, Analytical GREEnness metric (AGREE) calculator, and ComplexGAPI.

Multi-walled CNTs with an average diameter of about 80 nm, a length of several micrometers and surface area (SBET) of 100 m2 g-1 were obtained by pyrolysis of low-density polyethylene waste. The potential of the resulting MWCNTs material to purify water containing organic dyes was tested with Bezaktiv Blau HE-RM (BB) and Bezaktiv Rot S-3B (BR) reactive dyes. 200 mg L-1 MWCNT material was used to follow the adsorption of 30 mg L-1, 40 mg L-1, 50 mg L-1 and 60 mg L-1 BB and BR at pH 3 and a temperature of ~25 oC. The results have shown that this material has a high potential as a sorbent, and its adsorption capacity of 257 mg g-1 (for Bezaktiv Blau HE-RM) and 213 mg g-1 (for Bezaktiv Rot) is close to some commercial MWCNTs and functionalized MWCNT-based adsorbents. The adsorption process was very fast, reaching 80-90 % of the dye removal in 10-15 minutes, and the equilibrium time was reached in 40-60 minutes. The adsorption isotherm showed that the Langmuir model was more suitable than the Freundlich model for describing the adsorption properties of the pollutants.

From the whole plant of Barleria prionitis Linn. collected in Laos, six phenylethanoid glycosides, acetylmartynoside A (1), martynoside (2), 3-O-methylpoliumoside (3), isoaceteoside (4), leucosceptoside A (5), 2-(3-hydroxy-4-methoxyphenyl)-ethyl-O-(α-l-rhamnosyl)-(1-3)-O-(α-l-rhamnos-yl)-(1-6)-4-O-E-feruloyl-β-d-glucopyranoside (6) were isolated. Their structures were elucidated by 1D and 2D NMR and mass spectra. In addition, the antioxidant activity of compounds 1-6 was investigated. All of the compounds showed Keap1 protein inhibitory effect with binding affinity in the range of -9.639 - -9.084 kcal/mol and moderate DPPH free radical scavenging activity with their IC50 values in the range of 110-389 μM. Furthermore, the predicted toxicity results of all of them indicated a level of 5 and a high LD50 value (LD50 = 5000 mg/kg), which showed low toxicity and high safety for oral consumption in humans.

Phenazine and 6,13-diazapentacene are nitrogen-containing linear heterocycles that have attracted significant attention in the fields of organic electronics, and materials science. A straightforward strategy has been developed to construct 1,4,6,9-tetraarylphenazines and 5,7,12,14-tetraaryl-6,13-diazapentacenes with 1,4,6,9-tetrabromophenazine and 5,6,12,14-tetrabromo-6,13-dihydrodibenzo[b,i]phenazine as the key intermdiates, which were obtained easily from the bromination of phenazine and 6,13-dihydrodibenzo[b,i]phenazine, respectively. While the Pd-132 catalyzed ligand-free Suzuki couplings between above ascribed intermediates and various arylboronic acids were performed to afford directly tetraarylphenazines or tetraaryl-6,13-diazapentacenes by sequent oxidations. All of the new compounds are fully characterized by spectroscopy.

Two new copper(II) complexes, [Cu(HL)(ONO2)]NO3 (1) and [CuCl(HL)]Cl∙H2O (2), where HL is the zwitterionic form of the Schiff base 5-bromo-2-((2-piperazin-1-ylethylimino)methyl)phenol (HL), have been prepared. The Schiff base and two complexes were characterized by IR and UV-Vis spectroscopy. In addition, the free Schiff base was characterized by 1H NMR spectroscopy. Structures of the complexes were further confirmed by single crystal X-ray diffraction. The Cu atoms in the complexes are in square planar coordination. Crystal structures of both copper complexes are stabilized by hydrogen bonds. The complexes have high catalytic activity for the epoxidation of styrene, with conversions and selectivity over 90%.

The study examines the development of chemical literacy in non-formal learning environments based on a systematic literature review conducted between 2010 and 2023. Non-formal education serves as a valuable complement to the formal school system, enabling the exploration of topics often overlooked in formal curricula due to rigid regulations or teachers' lack of expertise. The review included 236 primary articles, of which 19 met strict inclusion criteria. The results indicate that the most employed approaches in non-formal education are inquiry-based learning, laboratory work with an emphasis on independent experimental activities, and science camps. Non-formal education significantly contributes to the development of chemical literacy, fosters interest in science, and improves attitudes toward chemistry. The authors highlight the need for further research in this field and greater integration of non-formal approaches into formal education to enhance the scientific literacy of young learners.

New complexes of zinc (1), manganese(II) (2 and 2a), cobalt(II) (3) and nickel(II) chloride (4), with pyzaH (pyrazine-2-carboxylic acid) were synthesized. The pyzaH molecules are coordinated as monodentate ligands only through heterocyclic nitrogen in 1, 2 and 3, as shown by single crystal X-ray diffraction analysis. The chloride ions are coordinated as terminal ligands in 1, [ZnCl2(pyzaH)2]×2H2O, but act as bridging ligands in the 1D complexes [MCl2(pyzaH)2]n×2nH2O (M = Mn, 2, Co, 3). The supramolecular architectures of the complexes differ due to the coordination of the chlorides, the hydrogen bonds and the parallel stacking arrangements of the pyzaH molecules. In contrast to the isolated crystals of 1, 2 and 3, the manganese(II) (2a) and nickel(II) (4), compounds do not contain water.  According to the IR spectra and the results of thermal analyzes, the proposed formula is [MCl2(pyzaH)2]. Powder X-ray and thermal analysis results demonstrate the isostructural nature of complexes 2a and 4. The low thermal stability of 1 is due to the monodentate coordination of pyzaH in 1. Thermal decomposition of 1, 2a and 4 in air produces oxides MO (M = Mn, Ni, Zn).