Publications

Microwave irradiation of Ni, Co, Cu, Ag, and Pt metal salts supported on graphite and charcoal revealed a series of carbon surface modification processes that varied depending on the conditions used (inert atmosphere, vacuum, or air) and the nature of metal salt. Carbon materials, routinely used to prepare supported metal catalysts and traditionally considered to be innocent on this stage, were found to actively change under the studied conditions: etching and pitting of the carbon surface by metal particles as well as growth of carbon nanotubes were experimentally observed by FE-SEM analysis. Catalyst preparation under microwave irradiation led to the formation of complex metal/carbon structures with significant changes in carbon morphology. These findings are of great value in developing an understanding of how M/C catalysts form and evolve and will help to design a new generation of efficient and stable catalysts. The energy surfaces of carbon support modification processes were studied with theoretical calculations at the density functional level. The energy surface of the multistage process of carbon nanotube formation from an etched graphene sheet was calculated for various types of carbon centers. These calculations indicated that interconversion of graphene layers and single wall carbon nanotubes is possible when cycloparaphenylene rings act as building units.

Rapid progress in the field of ionic liquids in recent decades led to the development of many outstanding energy-conversion processes, catalytic systems, synthetic procedures, and important practical applications. Task-specific optimization emerged as a sharpening stone for the fine-tuning of structure of ionic liquids, which resulted in unprecedented efficiency at the molecular level. Ionic-liquid systems showed promising opportunities in the development of green and sustainable technologies; however, the chemical nature of ionic liquids is not intrinsically green. Many ionic liquids were found to be toxic or even highly toxic towards cells and living organisms. In this Review, we show that biological activity and cytotoxicity of ionic liquids dramatically depend on the nature of a biological system. An ionic liquid may be not toxic for particular cells or organisms, but may demonstrate high toxicity towards another target present in the environment. Thus, a careful selection of biological activity data is a must for the correct assessment of chemical technologies involving ionic liquids. In addition to the direct biological activity (immediate response), several indirect effects and aftereffects are of primary importance. The following principal factors were revealed to modulate toxicity of ionic liquids: i) length of an alkyl chain in the cation; ii) degree of functionalization in the side chain of the cation; iii) anion nature; iv) cation nature; and v) mutual influence of anion and cation.

A unique nickel-based catalytic system was developed where the direction of the hydrophosphorylation reaction can be controlled by varying the catalyst loading. A flexible one-pot access to vinylmonophosphonates and alkylbisphosphonates was demonstrated using simple starting materials in an atom-economic reaction without any specific solvents or ligands. Monitoring of the reaction mechanism with joint NMR and MS studies revealed key information about the reaction intermediates. The synthetic scope of the developed catalytic system was explored and the utility of the synthesized products for the fire protection of cotton materials was demonstrated.

Experimental and theoretical investigation of the regiodivergent palladium-catalyzed dimerization of terminal alkynes is presented. Employment of N-heterocyclic carbene-based palladium catalyst in the presence of phosphine ligand allows for highly regio- and stereoselective head-to-head dimerization reaction. Alternatively, addition of carboxylate anion to the reaction mixture triggers selective head-to-tail coupling. Computational studies suggest that reaction proceeds via the hydropalladation pathway favoring head-to-head dimerization under neutral reaction conditions. The origin of the regioselectivity switch can be explained by the dual role of carboxylate anion. Thus, the removal of hydrogen atom by the carboxylate directs reaction from the hydropalladation to the carbopalladation pathway. Additionally, in the presence of the carboxylate anion intermediate, palladium complexes involved in the head-to-tail dimerization display higher stability compared to their analogues for the head-to-head reaction.

A unique Ni-catalyzed transformation is reported for the one-pot highly selective synthesis of previously unknown monoseleno-substituted 1,3-dienes starting from easily available terminal alkynes and benzeneselenol. The combination of a readily available catalyst precursor, Ni(acac)₂, and an appropriately tuned phosphine ligand, PPh₂Cy, resulted in the exclusive assembly of the s-gauche diene skeleton via the selective formation of C–C and C–Se bonds. The unusual diene products were stable under regular experimental conditions, and the products maintained the s-gauche geometry both in the solid state and in solution, as confirmed by X-ray analysis and NMR spectroscopy. Thorough mechanistic studies using ESI-MS revealed the key Ni-containing species involved in the reaction.

An NMR study of 10 l-alanine- and l-valine-containing peptides was carried out in the native [C₂MIM][Cl], [C₄MIM][Cl], [C₆MIM][Cl], [C₄MIM][BF₄], [C₄MIM][PF₆], and [C₄Py][BF₄] ionic liquid media. A unique high sensitivity of the ionic liquid system to the nature of peptide and ability to tune solvent–solute interactions were observed in contrast to regular organic solvents. The l-valine peptides can be selectively dissolved in [C₄MIM][Cl] and [C₆MIM][Cl], whereas their solubility in [C₂MIM][Cl] and other ionic liquids was dramatically lower. In spite of structural similarity between the amino acids, a distinct behavior was observed for the l-alanine peptides. Solvent–solute interactions with an ionic liquid impose significant changes, and NMR spectroscopy is a useful probe for the molecular-level and nanoscale organization of the studied systems. An even/odd effect of the number of amino acids in the peptide on molecular interactions in ionic liquids was observed. Enhancement of chemical properties of peptides in ionic liquids and application of ionic liquids in the separation of peptides are the areas of practical interest in the studied systems.

The experimental study of dechlorination activity of a Au/Ag bimetallic system has shown formation of a variety of chlorinated bimetallic Au/Ag clusters with well-defined Au:Ag ratios from 1:1 to 4:1. It is the formation of the Au/Ag cluster species that mediated C–Cl bond breakage, since neither Au nor Ag species alone exhibited a comparable activity. The nature of the products and the mechanism of dechlorination were investigated by ESI-MS, GC-MS, NMR, and quantum chemical calculations at the M06/6-311G(d)&SDD level of theory. It was revealed that formation of bimetallic clusters facilitated dechlorination activity due to the thermodynamic factor: C–Cl bond breakage by metal clusters was thermodynamically favored and resulted in the formation of chlorinated bimetallic species. An appropriate Au:Ag ratio for an efficient hydrodechlorination process was determined in a joint experimental and theoretical study carried out in the present work. This mechanistic finding was followed by synthesis of molecular bimetallic clusters, which were successfully involved in the hydrodechlorination of CCl ₄ as a low molecular weight environment pollutant and in the dechlorination of dichlorodiphenyltrichloroethane (DDT) as an eco-toxic insecticide. High activity of the designed bimetallic system made it possible to carry out a dechlorination process under mild conditions at room temperature.

Attachment of palladium clusters to carbon surface was investigated by SEM and STEM methods that have suggested plausible modification of chemical interactions across graphene layers; the fact can explain mismatches between domain structures and alignment patterns of palladium nanoparticles observed experimentally by the electron microscopy.

Acetonitrile solutions of nickel(II) acetylacetonate, which is ubiquitously used in different fields of organometallic chemistry and catalysis, were investigated by means of electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS). The detected Ni₂(acac)₃⁺ ion with the binuclear Ni₂O₂ core underwent a wide range of reactions after collision-induced dissociation, leading to a variety of products. Activation of C–H, C–C, and C–O bonds was observed involving the binuclear nickel complex. In sharp contrast, similar ions involving mononuclear and trinuclear nickel species did not show such exceptional behavior. The findings may open a fascinating direction in the field of superatoms to develop new chemical transformations for organometallic chemistry and catalysis. The higher relative stability of binuclear species was also observed in ESI mass spectra of copper and vanadyl complexes with acetylacetonate ligands, Cu₂(acac)₃⁺ and (VO)₂(acac)₃⁺. An important point concerns the purity of the studied solutions, since even a trace level of contaminants has drastically diminished the outcome of the mechanistic studies.