Toward Totally Defined Nanocatalysis: Deep Learning Reveals the Extraordinary Activity of Single Pd/C Particles

Eremin D.B., Galushko A.S., Boiko D.A., Pentsak E.O., Chistyakov I.V., Ananikov V. P., J. Am. Chem. Soc., 2022, 144, 6071–6079.
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Homogeneous catalysis is typically considered "well-defined" from the standpoint of catalyst structure unambiguity. In contrast, heterogeneous nanocatalysis often falls into the realm of "poorly defined" systems. Supported catalysts are difficult to characterize due to their heterogeneity, variety of morphologies, and large size at the nanoscale. Furthermore, an assortment of active metal nanoparticles examined on the support are negligible compared to those in the bulk catalyst used. To solve these challenges, we studied individual particles of the supported catalyst. We made a significant step forward to fully characterize individual catalyst particles. Combining a nanomanipulation technique inside a field-emission scanning electron microscope with neural network analysis of selected individual particles unexpectedly revealed important aspects of activity for widespread and commercially important Pd/C catalysts. The proposed approach unleashed an unprecedented turnover number of 109 attributed to individual palladium on a nanoglobular carbon particle. Offered in the present study is the Totally Defined Catalysis concept that has tremendous potential for the mechanistic research and development of high-performance catalysts.

Intermolecular Photocatalytic Chemo-, Stereo- and Regioselective Thiol-yne-ene Coupling Reaction

Burykina Ju.V., Kobelev A.D., Shlapakov N.S., Kostyukovich A.Yu., Fakhrutdinov A.N., König B., Ananikov V.P., Angew. Chem. Int. Ed., 2022, 61, e202116888.
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The first example of an intermolecular thiol-yne-ene coupling reaction is reported for the one-pot construction of C-S and C-C bonds. This opens a new dimension in building molecular complexity to access densely functionalized products. The progress was achieved by suppressing hydrogen atom transfer (HAT) and associative reductant upconversion (via associative electron upconversion C-S three-electron σ-bond formation) using an Eosin Y/DBU/MeOH photocatalytic system. Investigation of the reaction mechanism by combining online ESI-UHRMS, EPR spectroscopy, isotope labeling, determination of quantum yield and computational modeling revealed a unique photoredox cycle with four radical-involving stages. Previously unavailable products of the thiol-yne-ene reaction were obtained in good yields with high selectivity and can serve as stable precursors for the synthesis of synthetically demanding activated 1,3-dienes.

One-Step Access to Heteroatom-Functionalized Imidazol(in)ium Salts

Pasyukov D., Shevchenko M., Shepelenko K., Khazipov O., Burykina Ju.V., Gordeev E.G., Minyaev M.E., Chernyshev V.N., Ananikov V. P., Angew. Chem. Int. Ed., 2022, 61, e202116131.
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Imidazolium salts have ubiquitous applications in energy research, catalysis, materials and medicinal sciences. Here, we report a new strategy for the synthesis of diverse heteroatom-functionalized imidazolium and imidazolinium salts from easily available 1,4-diaza-1,3-butadienes in one step. The strategy relies on a discovered family of unprecedented nucleophilic addition/cyclization reactions with trialkyl orthoformates and heteroatomic nucleophiles. To probe general areas of application, synthesized N-heterocyclic carbene (NHC) precursors were feasible for direct metallation to give functionalized M/carbene complexes (M = Pd, Ni, Cu, Ag, Au), which were isolated in individual form. The utility of chloromethyl function for the postmodification of the synthesized salts and Pd/carbene complexes was demonstrated. The obtained complexes and imidazolium salts demonstrated good activities in Pd- or Ni-catalyzed model cross-coupling and C-H activation reactions.

Nickel and Palladium Catalysis: Stronger Demand than Ever

Chernyshev V.M., Ananikov V.P., ACS Catal., 2022, 12, 1180-1200.
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Key similarities and differences of Pd and Ni in catalytic systems are discussed. Overall, Ni and Pd catalyze a vast number of similar C–C and C–heteroatom bond-forming reactions. However, the smaller atomic radius and lower electronegativity of Ni, as well as the more negative redox potentials of low-valent Ni species, often provide higher reactivity of Ni systems in oxidative addition or insertion reactions and higher persistence of alkyl-Ni intermediates against β-hydrogen elimination, thus enabling activation of more reluctant electrophiles, including alkyl electrophiles. Another key point relates to the higher stability of the open-shell electronic configurations of Ni(I) and Ni(III) compared with Pd(I) and Pd(III). Nickel systems very often involve a number of interconvertible Ni(n+) active species of variable oxidation states (Ni(0), Ni(I), Ni(II), and Ni(III)). In contrast, catalytic reactions involving Pd(I) or Pd(III) active species are still relatively less developed and may require facilitation by special ligands or merging with photo- or electrocatalysis. However, the relatively high redox potentials of Pd(n+) species ensure their facile reduction to Pd(0) species under the assistance of numerous reagents or solvents, providing relatively high concentrations of molecular Pd1(0) complexes that can reversibly aggregate into active Pdn clusters and nanoparticles to form a cocktail of interconvertible Pdn(0) active species of various nuclearities (i.e., various values of "n"). Nickel systems involving Ni(0) complexes often require special strong reductants; they are more sensitive to deactivation by air and other oxidizers and, as consequence, often operate at higher catalyst loadings than palladium systems in the same reactions. The ease of activation and relatively high stability of low-valent active Pd species provide high robustness and versatility for palladium catalysis, whereas a variety of Ni oxidation states enables more diverse and uncommon reactivity, albeit requiring higher efforts in the activation and stabilization of nickel catalytic systems. As a point for discussion, we may note that Pd catalytic systems may easily form a "cocktail of particles" of different nuclearities but similar oxidation states (Pd1, Pdn, Pd NPs), whereas nickel may behave as a "cocktail of species" in different oxidation states but is less variable in stable nuclearities. Undoubtedly, there is stronger demand than ever not only to develop improved efficient catalysts but also to understand the mechanisms of Pd and Ni catalytic systems.

Generation, regeneration, and recovery of Cu catalytic system by changing the polarity of electrodes

Rodygin K.S., Samoylenko D.E., Seitkalieva M.M., Lotsman K.A., Metlyaeva S.A., Ananikov V.P. , Green Chem., 2022, 24, 1132-1140.
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Considering a complete life cycle of metal catalysts, metals are usually mined from ores as salts (MX′n), industrially processed to the bulk metal (M) and then converted into the salts again (MXn) to be used as catalyst precursors. Under catalytic conditions, metal salts undergo transformations to form catalytically active species (MLn), and the anion (X) is typically converted to waste. Thus, there are extra steps before a catalytic process may start, and the chemical transformation involved therein generates considerable amounts of waste. Here, we study the strategy for merging electrodissolution with catalysis to skip these extra steps and demonstrate efficient waste-minimized transformations to access Cu catalysts from the metal. Bulk metal from an electrode can be transformed directly into a catalytic reaction under the action of electric current. As a representative example, dipolar addition of azides to alkynes was successfully catalyzed by copper metal. The reaction was carried out in an ionic liquid (IL), which acted simultaneously as an electrolyte, a solvent and stabilizer of the formed catalytically active species. The used catalyst can be regenerated (or reactivated, if necessary) by application of reverse polarity of electrodes and directly reused again. For metal and solvent recovery, the ILs used were easily separated from copper species by passing an electric current. The applicability of the copper-catalyzed transformation was additionally tested for cross-coupling of thiols with aryl halides (the Ullmann reaction), click reaction with calcium carbide and three-component azide–halide–alkyne coupling. The mechanism of copper dissolution from an electrode was studied, and the intermediates were identified by means of XRD, X-ray and HRESI-MS.

Metal-Catalyzed Chemical Activation of Calcium Carbide: New Way to Hierarchical Metal/Alloy-on-Carbon Catalysts

Lebedev A.N., Rodygin K.S., Mironenko R.M., Saybulina E.R, Ananikov V.P., J. Catal, 2022, 407, 281-289.
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A simple and efficient strategy for the synthesis of "metal/alloy–on–carbon" catalysts was developed. A highly ordered extra pure graphite-like carbon material as a catalyst support was obtained after calcium carbide decomposition at 700 °C in a stream of gaseous chlorine. When Pd, Pt, Ag, Au, Co, Ni, Fe, Cu salts were added to calcium carbide prior to decomposition, a metal was reduced from a salt by elemental carbon, despite an oxidizing atmosphere. Metal particles were formed on the surface of the layered carbon material, covered with a thin layer of high–purity carbon and partially immersed in it. A catalytically active remaining metal was available for organic molecules due to the porous structure of carbon. At the same time, a metal was firmly held inside the carbon shells and was not washed out during a reaction and after washing procedures, keeping its catalytic activity unchanged for several cycles. Mixing various salts together before the reaction led to the alloys, and the ratio of the salts simply determined the ratio of the metals in the desired alloy. This approach allowed the synthesis of highly active metals/alloys on carbon catalysts with intrinsic hierarchical organization, which ensures a long-life cycle in the reaction. The obtained catalysts were successfully tested in the Suzuki-Miyaura cross-coupling reaction and showed excellent stability with a yield change <1% over several cycles (compared with a 64% yield decrease of commercial catalyst). the obtained catalysts have also shown very good performance in the semihydrogenation of c≡c bonds in phenylacetylene and other alkynes with selectivity up to 96% at 99% conversion.

Merging structural frameworks of imidazolium, pyridinium, and cholinium ionic liquids with cinnamic acid to tune solution state behavior and properties

Vavina A.V., Seitkalieva M.M., Posvyatenko A.V., Gordeev E.G., Strukova E.N., Egorova K.S., Ananikov V.P., J. Mol. Liq., 2022, 352, 118673.
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Solubility in water, interactions with the solvent medium and tuning of molecular conformation in the liquid phase are the key issues to discover new biologically active molecules and to understand the mechanisms of their action. In the present article, we report synthesis, structural and biological activity studies, and computational modeling of new ionic compounds. Structural frameworks of well-known imidazolium, pyridinium and cholinium ionic liquids (ILs) were combined with naturally occurring cinnamic acid (CA), which is known to possess a wide spectrum of biological activity. Different combinations of these two structural elements (IL and Cin (cinnamic moiety)) allowed modulating the solubility, physicochemical properties and biological activity of the resulting molecules. A significant increase in the biological activity was achieved for the three studied hybrid molecules - [C4mim-Cin][Cl], [C4py–Cin][Cl], and [C4mim-Cin][Cin]. Multiparameter cytotoxicity mapping was performed to visualize the biological activity of the 28 studied molecules. Detailed experimental investigation and molecular dynamics simulation were performed to gain insight into the structure–activity relationship. Of note, a folding conformational change in the structure of [Cnmim-Cin][Cl] hybrid molecules in solution resulted in a substantial change in chemical reactivity, with the activation energy of the hydrolysis reaction decreasing from 32.1 to 23.9 kcal/mol.

Evidence for the “cocktail” nature of platinum-catalyzed alkyne and alkene hydrosilylation reactions

Ondar E.O., Burykina Ju.V., Ananikov V. P., Catal. Sci. Technol., 2022, 12, 1173-1186.
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Evidence of the involvement of a "cocktail"-type catalytic system in the alkyne and alkene hydrosilylation reaction in the presence of platinum on a carbon support is reported. The nature of the catalytic system was studied by employing a consistently developed experimental procedure. The existence of a "cocktail"-type catalysis pathway was shown for the hydrosilylation reaction catalyzed by platinum on multiwalled carbon nanotubes (Pt/MWCNT) and platinum on charcoal (Pt/C), with silane variation. The type of catalyst had a significant influence on the "cocktail"-type system formation. Involvement of a multichannel catalytic system requires critical rethinking of the principles of catalyst design. Another approach should be utilized to achieve high activity, stability and recycling compared to classical heterogeneous catalytic systems.

Thermal Mapping of Self-Promoted Calcium Carbide Reactions for Performing Energy-Economic Processes

Rodygin K.S., Lotsman K.A., Erokhin K.S., Korabelnikova V.A., Ananikov V.P., Int. J. Mol. Sci., 2022, 23, 2763.
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The syntheses of various chemical compounds require heating. The intrinsic release of heat in exothermic processes is a valuable heat source that is not effectively used in many reactions. In this work, we assessed the released heat during the hydrolysis of an energy-rich compound, calcium carbide, and explored the possibility of its usage. Temperature profiles of carbide hydrolysis were recorded, and it was found that the heat release depended on the cosolvent and water/solvent ratio. Thus, the release of heat can be controlled and adjusted. To monitor the released heat, a special tube-in-tube reactor was assembled using joining part 3D-printed with nylon. The thermal effect of the reaction was estimated using a thermoimaging IR monitor. It was found that the kinetics of heat release are different when using mixtures of water with different solvents, and the maximum achievable temperature depends on the type of solvent and the amount of water and carbide. The possibility of using the heat released during carbide hydrolysis to initiate a chemical reaction was tested using a hydrothiolation reaction—the nucleophilic addition of thiols to acetylene. In a model experiment, the yield of the desired product with the use of heat from carbide hydrolysis was 89%, compared to 30% in this intrinsic heating, which was neglected.

Preparation of Hybrid Sol-Gel Materials Based on Living Cells of Microorganisms and Their Application in Nanotechnology

Kamanina O.A., Saverina E.A., Rybochkin P.V., Arlyapov V.A., Vereshchagin A.N., Ananikov V.P, Nanomaterials, 2022, 12, 1086.
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Microorganism-cell-based biohybrid materials have attracted considerable attention over the last several decades. They are applied in a broad spectrum of areas, such as nanotechnologies, environmental biotechnology, biomedicine, synthetic chemistry, and bioelectronics. Sol-gel technology allows us to obtain a wide range of high-purity materials from nanopowders to thin-film coatings with high efficiency and low cost, which makes it one of the preferred techniques for creating organic-inorganic matrices for biocomponent immobilization. This review focuses on the synthesis and application of hybrid sol-gel materials obtained by encapsulation of microorganism cells in an inorganic matrix based on silicon, aluminum, and transition metals. The type of immobilized cells, precursors used, types of nanomaterials obtained, and their practical applications were analyzed in detail. In addition, techniques for increasing the microorganism effective time of functioning and the possibility of using sol-gel hybrid materials in catalysis are discussed.

Integration of thermal imaging and neural networks for mechanical strength analysis and fracture prediction in 3D-printed plastic parts

Boiko D.A., Korabelnikova V.A., Gordeev E.G., Ananikov V.P., Sci. Rep., 2022, 12, 3780.
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Additive manufacturing demonstrates tremendous progress and is expected to play an important role in the creation of construction materials and final products. Contactless (remote) mechanical testing of the materials and 3D printed parts is a critical limitation since the amount of collected data and corresponding structure/strength correlations need to be acquired. In this work, an efficient approach for coupling mechanical tests with thermographic analysis is described. Experiments were performed to find relationships between mechanical and thermographic data. Mechanical tests of 3D-printed samples were carried out on a universal testing machine, and the fixation of thermal changes during testing was performed with a thermal imaging camera. As a proof of concept for the use of machine learning as a method for data analysis, a neural network for fracture prediction was constructed. Analysis of the measured data led to the development of thermographic markers to enhance the thermal properties of the materials. A combination of artificial intelligence with contactless nondestructive thermal analysis opens new opportunities for the remote supervision of materials and constructions.

Exploring metallic and plastic 3D printed photochemical reactors for customizing chemical synthesis

Gordeev E.G., Erokhin K.S., Kobelev A.D., Burykina Ju.V., Novikov P.V., Ananikov V. P., Sci. Rep., 2022, 12, 3780.
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Visible light photocatalysis is a rapidly developing branch of chemical synthesis with outstanding sustainable potential and improved reaction design. However, the challenge is that many particular chemical reactions may require dedicated tuned photoreactors to achieve maximal efficiency. This is a critical stumbling block unless the possibility for reactor design becomes available directly in the laboratories. In this work, customized laboratory photoreactors were developed with temperature stabilization and the ability to adapt different LED light sources of various wavelengths. We explore two important concepts for the design of photoreactors: reactors for performing multiple parallel experiments and reactors suitable for scale-up synthesis, allowing a rapid increase in the product amount. Reactors of the first type were efficiently made of metal using metal laser sintering, and reactors of the second type were successfully manufactured from plastic using fused filament fabrication. Practical evaluation has shown good accuracy of the temperature stabilization in the range typically required for organic synthesis for both types of reactors. Synthetic application of 3D printed reactors has shown good utility in test reactions—furan C–H arylation and thiol-yne coupling. The critical effect of temperature stabilization was established for the furan arylation reaction: heating of the reaction mixture may lead to the total vanishing of photochemical effect.

Comparative assessment of heterogeneous and homogeneous Suzuki-Miyaura catalytic reactions using bio-Profiles and bio-Factors

Pentsak E.O., Dzhemileva L.U., D'yakonov V.A., Shaydullin R.R., Galushko A.S., Egorova K.S., Ananikov V.P., J. Organomet. Chem., 2022, 122319.
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Transition metals are essential for most catalytic systems in fine organic synthesis. The usage of transition metals has traditionally raised concerns about their toxicity and potential environmental pollution problems. In this context, the issue of preference for supported catalysts, which can be easily removed from the reaction mixture, over metal complex catalysts is of significant relevance. In this work, we used bio-Profiles and bio-Factors of chemical reactions to assess the impact of catalyst type on the toxicity of a reaction system in the practically important Suzuki-Miyaura reaction. The supported catalysts had noticeably lower cytotoxicity than soluble metal complex catalysts. However, the combined effect of supported catalysts on the environment can depend on their preparation procedure and may have a noticeable "neglected" biological impact. Both types of catalysts made no significant contribution to the "overall toxicity" of the systems studied, while common and typically ignored byproducts demonstrated significantly higher "overall" biological influence. In the present study, we describe how to use bio-Profiles in order to visualize and analyze the biological properties of different types of catalytic reactions.