The dinuclear nickel(II) complex [Ni2LmClO4] + , where Lm represents a 24-membered macrocyclic hexaaza-dithiophenolate ligand, reacts with 5-(4-pyridyl)tetrazole (PyrCN4H) to give the dinuclear complex [Ni2Lm(PyrCN4)]+ . The new complex was both isolated as perchlorate or tetraphenylborate salts and characterised by elemental analysis and IR spectroscopy. The structure of [Ni2Lm(PyrCN4)]BPh4 ⋅ MeCN was determined by single crystal X-ray diffraction, showing that tetrazolate units are in a N2,N3-bridging mode to generate dioctahedral N3Ni(µ-S)2(µ-N4CPyr)NiN3 core.
It was shown that N2O content among NO reduction products increases with an increase of the silver concentration in the catalyst because the nature of the catalytic centers changes and leads to a subsequent change in the mechanism of the reaction. Two reaction mechanisms were proposed and studied by means of quantum chemistry: a two-stage mechanism that proceeds via NO dimer formation on catalysts with high (above 2 wt. %) silver concentration and a parallel mechanism with isocyanates involved on catalysts with low (below 2 wt. %) silver concentration. It was demonstrated that on catalysts with high silver concentration mechanism that involves stepwise NO reduction via N2O to N2 is realised. Moreover, the final stage is complicated by the fact that formed intermediates and N2O are likely to desorb from the catalyst surface. In the case of catalysts with low silver concentration, the formation of both products (N2O and N2) proceeds in parallel and the lower activation barriers of the reaction leading to N2, as well as the thermodynamic profitability of its formation, lead to the predominance of the target product. The competition between the proposed mechanisms was studied in the case of catalytic centers represented by silver dimers. It was shown that activation barriers of reaction proceeding via NO dimer formation are lower than the corresponding barriers of the reaction with isocyanates involved, which confirms the prevalent realisation of the first process and the predominance of N2O among the final products. The obtained results explain the experimental data and are significant for further modelling of the mechanism of nitrogen oxides catalytic reduction considering the Al2O3 support.
The adsorption of the cephalosporin antibiotic sodium cefotaxime (CEFOT) on two activated carbons in the temperature range 288–313 K was under study. Experimental charcoal AC obtained from hydrolysis lignin was established to be mesoporous. It demonstrates greater CEFOT adsorption activity than the commercially available charcoal OU-A made from wood and characterized by both micro- and mesoporous structure. The surface modification of both activated carbons by a water-soluble polyelectrolyte cellulose acetate sulfate in the form of sodium salt (Na-CAS) leads to an increase in specific adsorption. The multilayer model with saturation (MMS) was used for data analysis. As a result, the number of molecules on the adsorption center, the density of adsorption centers, the total number of formed layers and the energy characteristics of adsorbate – adsorbent interactions at the interface and adsorbate – adsorbate ones within the adsorption layer were estimated.
The target for antibacterial action of 1,4-di- and 1,4,5-trisubstituted 1H-1,2,3-triazoles against E. coli ATCC 25922 and S. aureus ATCC 6538 was proposed. Structures of target proteins and investigated triazoles were built using molecular modeling. Binding mechanism was suggested according to conducted docking studies. Suggested binding models and affinity for a binding site of 1,4-disubstituted 1H-1,2,3-triazoles correlated with their experimental activity. Further functionalization directions for continuation of a search for a novel effective antibacterial agents were discovered.
The structure of copper(II) poly-5-vinyltetrazolate and the products of its thermolysis has been studied by means of density functional theory and infrared spectroscopy. Copper(II) poly-5-vinyltetrazolate has been obtained and subsequently subjected to thermolysis. Infrared spectra of copper(II) poly-5-vinyltetrazolate and the products of its thermolysis have been recorded. The possible ways of coordination of copper(II) ions with tetrazole-containing ligands were established by analyzing the calculated molecular electrostatic potential distribution and comparing the calculated IR-spectra of the model structures to the experimental ones. It has been shown that the best agreement between the calculated and experimental data is observed for the model with three-coordinated copper(II) ions, which includes both the tetrazole-containing ligands coordinating two copper(II) ions through N(1)- and N(3)-atoms of the tetrazole ring, and the tetrazolecontaining ligands coordinating one copper(II) ion through either the N(2)- or the N(3)-atom. Recently we have shown that the product of thermolysis of copper(II) poly-5-vinyltetrazolate exhibits high catalytic activity in homocoupling of phenylacetylene and Huisgen [3 + 2]-cycloaddition. To establish the structure of the products of thermolysis of copper(II) poly-5-vinyltetrazolate, seven possible products have been proposed based on the analysis of the structure of copper(II) poly-5-vinyltetrazolate and the experimental IR-spectrum. IR-spectra of all proposed products have been calculated and the results of the calculations have been compared with the experimental IR-spectrum of copper(II) poly-5-vinyltetrazolate thermolysis product. It has been shown that the main product of thermolysis is cis-polycyanoacetylene.
It has been shown that the WP04 functional in combination with moderate basic sets 6-31G(d) and SDD allows to calculate characteristics of 1H NMR-spectrum of metal complexes with ligands based on tetrazole derivatives with high accuracy, which can be used to assign signals in the NMR-spectra. The process of hydrolysis of the isomeric platinum(II) chloride complexes with (2-isopropyltetrazol-5-yl)acetic acid has been investigated using the methods of quantum chemistry and NMR-spectroscopy. An explanation of the changes of signals in the 1H NMR-spectra of the considered complexes during their hydrolysis is given.
Optimization of the method for the synthesis of methylated poly-5-vinyltetrazole was carried out and it was shown that the process of its preparation, both with the homopolymer acrylonitrile and the commercially available copolymer with methyl acrylate and 2-acrylamido-2-methylpropane sulfonic acid, as starting materials, can be carried out in a single-step apparatus without intermediate release of poly-5-vinyltetrazole. At the same time, the resulting product is identical in composition, structure, and properties to that obtained using a two-stage process. Ability to refuse intermediate release of poly-5-vinyltetrazole allows to reduce the amount of dimethylformamide required for the preparation of methylated poly-5-vinyltetrazole twice, exclude the use of HCl solution from the process, and significantly reduce the time and energy costs of the process.
Complexes [MII(2-pytz)Cl2] (M(II) = Pt, Pd; 2-pytz = 2-(tetrazol-1-yl)pyridine) were synthesised via direct interaction of the corresponding metal chlorides (K2PtCl4 or PdCl2) with 2-pytz under ambient conditions. RuCl3 does not react with 2-pytz under reflux in the protic media, while under reflux in N, N-dimethylformamide in the presence of LiCl, decomposition of the tetrazole cycle occurred leading to the formation of Ru(III)-coordinated N, N-dimethyl-N ′-(pyridin-2-yl)formimidamide derivative Li[RuIII(Py — N =C — NMe2)2Cl2]. The complex [Ru(2-pytz)(DMSO)3Cl2] ⋅ MeOH, where DMSO is dimethyl sulfoxide, was synthesised by reacting a specially prepared precursor cis-[Ru(DMSO)4Cl2] with 2-pytz in methanol under reflux conditions. The complex [Ru(2-pytz)(DMSO)2Cl2] was synthesised by reacting cis-[Ru(DMSO)4Cl2] with 2-pytz in ethanol under reflux conditions. The resulting complexes were characterised by elemental analyses, electrospray ionisation mass-spectrometry with detection of positive and negative ions, infrared spectroscopy, 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, and simultaneous thermal analysis. The structures of complexes [Pd(2-pytz)Cl2] and [Ru(2-pytz)(DMSO)3Cl2] ⋅ MeOH were investigated by single-crystal X-ray analysis. In the former, 2-pytz shows a N,N-chelating coordination via the pyridine ring N and the tetrazole ring N2 atoms. In the latter, 2-pytz coordinates as a monodentate ligand via the tetrazole ring N4 atom. According to 1H NMR spectroscopy data, in complex [Ru(2-pytz)(DMSO)2Cl2], 2-pytz coordinates as a N, N-chelating ligand via the pyridine ring N and the tetrazole ring N2 atoms.
Novel tripodal ligands (R1N4CS)3CH, where R1 = Me, Ph, were synthesised by alkylation of 1-R-tetrazol-5-thioles with iodoform in alkaline media. These ligands were identified based on data of elemental analysis, nuclear magnetic resonance spectroscopy, thermal analysis, and X-ray diffraction analysis of single crystals.
Drawing the experience of 5-phenyl- and 5-pyridyltetrazoles, it was shown that classical nitration-reduction methods in combination with typical alkylation reactions of tetrazole derivatives can be used to obtain multitopic polynuclear tetrazole-containing ligands. Methods for the preparation of a number of previously undescribed polynuclear tetrazole derivatives, including those combining both tetrazole and pyridine rings in the molecule, have been developed. The composition and structure of the obtained compounds were determined by elemental analysis, single crystal X-ray diffraction, NMR and IR spectroscopy. For (5-(pyridin-2-yl)tetrazol-2-yl)(5-(pyridin-2-yl)tetrazol-1-yl)methane the crystalline structure was determined and it was found that this compound forms a 3D polymer framework due to non-classical hydrogen bonds. In its crystal structure there is a network of π – π stacking interactions between tetrazole rings of neighbouring molecules, as well as between pyridine rings.
Complexes [Сu(NCS)2L3], [Сu(NO3)2L4] and [Cu(NCS)2L4]·L have been prepared by direct synthesis involving the interaction of metallic copper, ammonium salts NH4X (Х = NCS, NO3) and 1-tert-butyl-1H-1,2,4-triazole (L). Their composition and structure were determined by elemental analysis, single crystal X-ray analysis, and IR spectroscopy (range of 4000–500 cm–1). All the complexes showed mononuclear structure. In them triazole acts as a monodentate ligand, being coordinated by the N4 atom of the heterocycle. The NCS– and NO–3 anions display monodentate N- and O-coordination, accordingly. In [Сu(NCS)2L3], copper(II) cation has square-pyramidal environment of nitrogen atoms of two ligands L and two thiocyanate anions in the basal sites, and one nitrogen atom of ligand L in the apical position. In complexes [Сu(NO3)2L4] and [Cu(NCS)2L4]·L, copper(II) cations are octahedrally surrounded by nitrogen atoms of ligand L in the equatorial sites and by O or N atoms of corresponding anions in the axial positions.
A novel facile method for the synthesis of 1-iso-propyl-1H-1,2,4-triazole (L) is described. This method is based on alkylation of 1,2,4-triazole with isopropyl alcohol in sulfuric acid media. It allows to synthesize the target product selectively with a yield of near 98 %. New coordination compounds [CuL2(Н2О)2Cl2] and [СuL4Cl2] were synthesized by the interaction of 1-iso-propyl-1H-1,2,4-triazole with copper(II) chloride dihydrate. Composition and structure of prepared complexes were studied by elemental analysis, X-ray diffraction analysis and IR spectroscopy. Both coordination compounds were found to be mononuclear complexes with octahedral coordination of copper atoms. Ligand L shows monodentate coordination through the triazole ring N4 atom. The analysis of the changes observed in the IR-spectrum of L under coordination with CuII atom was carried out. It was shown that IR spectroscopy can be used in order to study some structural peculiarities of azole complexes, in particular presence of bounded or coordinated water molecules and hydrogen bonds as well as localization of coordination bonds.
