Transition-Metal-Catalyzed C–S, C–Se, and C–Te Bond Formations via Cross-Coupling and Atom-Economic Addition Reactions. Achievements and Challenges

Beletskaya I.P., Ananikov V. P., Chem. Rev., 2022, 122, 16110–16293.
DOI link

In the present review, we discuss recent progress in the field of C–Z bond formation reactions (Z = S, Se, Te) catalyzed by transition metals. Two complementary methodologies are considered─catalytic cross-coupling reactions and catalytic addition reactions. The development of advanced catalytic systems is aimed at improved catalyst efficiency, reduced catalyst loading, better cost efficiency, environmental concerns, and higher selectivity and yields. The important rise of research efforts in sustainability and green chemistry areas is critically assessed. The paramount role of mechanistic studies in the development of a new generation of catalytic systems is addressed, and the key achievements, problems, and challenges are summarized for this field.

Fully Automated Unconstrained Analysis of High-Resolution Mass Spectrometry Data with Machine Learning

Boiko D.A., Kozlov K.S., Burykina Yu.V., Ilyushenkova V.V., Ananikov V.P. , J. Am. Chem. Soc., 2022, 144, 14590-14606.
DOI link

Mass spectrometry (MS) is a convenient, highly sensitive, and reliable method for the analysis of complex mixtures, which is vital for materials science, life sciences fields such as metabolomics and proteomics, and mechanistic research in chemistry. Although it is one of the most powerful methods for individual compound detection, complete signal assignment in complex mixtures is still a great challenge. The unconstrained formula-generating algorithm, covering the entire spectra and revealing components, is a "dream tool" for researchers. We present the framework for efficient MS data interpretation, describing a novel approach for detailed analysis based on deisotoping performed by gradient-boosted decision trees and a neural network that generates molecular formulas from the fine isotopic structure, approaching the long-standing inverse spectral problem. The methods were successfully tested on three examples: fragment ion analysis in protein sequencing for proteomics, analysis of the natural samples for life sciences, and study of the cross-coupling catalytic system for chemistry.

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.
DOI link

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 10 9 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.
DOI link

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.V., Shevchenko M.A., Shepelenko K.E., Khazipov O.V., Burykina J.V., Gordeev E.G., Minyaev M.E., Chernyshev V.M. and Ananikov V.P., Angew. Chem. Int. Ed., 2022, 61, e202116131.
DOI link

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.
DOI link

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.

“Hidden” Nanoscale Catalysis in Alkyne Hydrogenation with Well-Defined Molecular Pd/NHC Complexes

Denisova E.A., Kostyukovich A. Yu., Fakhrutdinov A. N., Korabelnikova V. A., Galushko A.S., and Ananikov V.P., ACS Catal., 2022, 12, 6980–6996.
DOI link

Pd/NHC complexes are widely used as catalysts in hydrogenation reactions. Usually, the operating mode of these systems is referred to as homogeneous. In this work, we demonstrated that mixed homogeneous–heterogeneous catalysis can be realized in the hydrogenation reaction when Pd/NHC complexes were used as precatalysts. Palladium NPs are formed in situ and act as "hidden" nanoscale catalysts. Based on the quantum chemical calculations and experimental XPS results, the presence of surface NHC ligands on metal nanoparticles can be proposed. Herein, we propose a method for the determination of dynamic transformations of Pd/NHC complexes in transfer hydrogenation reactions via 13C labeling and NMR spectroscopy. This approach is based on the introduction of a 13C label in the C2 position of the imidazolium fragment of Pd/NHC, which is unique to the M–NHC bond. It was found using NMR, ESI-MS, and TEM monitoring of the transfer semihydrogenation of diphenylacetylene that Pd/NHC complexes disappear from the reaction mixtures at the early stage of reaction. Palladium atoms pass into a heterogeneous phase, forming NPs with sizes ranging from 1 to 9 nm. The experimental study and calculations performed in the present study revealed the role of the ligands on the surface of metal nanoparticles. Comparative modeling of hydrogenation reactions on ligand-free and NHC-modified Pd clusters showed that modification of the metal surface increased the catalytic activity by reducing the potential barriers of the alkyne syn-addition and reductive elimination stages. Since the presence of an NHC ligand in the catalytic system leads to a change in the rate-limiting stage of the reaction, we proposed a combined reaction mechanism, according to which oxidative addition proceeds on a bare metal surface, and the remaining two stages occur in the modified zone of NPs.

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.
DOI link

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.
DOI link

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.

Towards Determining Molecular Structure with ESI-MS Backed by Computational Methods: Structures of Subnanoclusters of Pd and Cu Chlorides, Ion Dynamics in Vacuum, and Challenges to the Methodology

Bondarenko A.A., Vlasova Yu.S., Polynski M.V., Ilyushenkova V.V., Ananikov V.P. , Inorg. Chem. Front. , 2022, 9, 5279-5295.
DOI link

Many practically relevant inorganic solution systems have complex compositions with tens or hundreds of distinct species. Here, we present an approach to analyzing ESI-MS spectra combining a set of scripts for peak assignment and a quantum chemical methodology for the determination of the structure of selected ions. We selected solutions of CuCl, PdCl 2, and the CuCl–PdCl2 mixture as models of popular precatalysts in cross-coupling reactions and the Wacker process that can form "cocktail"-type systems. The spectra exhibited a great number of signals of mono- and bimetallic oligomeric chloride subnanoclusters. Few oligometallic ions had core–shell structures, according to the computations; the structure of most ions was completely unsymmetric, with bridging Cl ligands supporting the oligomeric structures. Born-Oppenheimer molecular dynamics showed that some ions were structurally flexible under the selected conditions. Many considered ions exhibited rich configurational and conformational isomerism. The activation (polarization) of the N2 molecule (from the drying gas used during electrospray ionization) by some ions was determined by the analysis of electron density distributions. For the first time, we describe a flexible approach for semiautomatic analysis of highly complex mass-spectra of organometallic systems in solution with the possibility of revealing molecular structures.

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.
DOI link

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.

Nmr-Monitoring Of H/D Exchange Reaction Of Ketones In Solutions Of Imidazolium Ionic Liquids

Shahkhatuni A.A., Shahkhatuni A.G., Ananikov V. P., Harutyunyan A.S. , J. Mol. Liq., 2022, 362, 119746.
DOI link

NMR spectroscopy was used to study hydrogen-deuterium exchange in CH3, CH2 and CH moieties of ketones dissolved in mixtures of solvents containing exchangeable deuteriums and imidazolium ionic liquids (IL) acting as catalysts. Factors affecting the efficiency of the exchange, as well as the role of the deuterated solvent, temperature and concentration, were investigated. Depending on the sample composition and temperature, the degree of deuteration can reach different values at equilibrium state, and the exchange rate can vary from several minutes to several months. ILs with OAc anions and with ethyl chain cations exhibit significant catalytic properties and high degrees of deuteration (up to 98%), which can be achieved by consecutive deuteration cycles. A convenient practical protocol for monitoring the exchange process by NMR spectroscopy and calculating the degree of deuteration was developed and can be used for various molecular systems.

Biological activity, solvation properties and microstructuring of protic imidazolium ionic liquids

Egorova K.S., Seitkalieva M.M., Kashin A.S., Gordeev E.G., Vavina A.V., Posvyatenko A.V., Ananikov V.P., J. Mol. Liq., 2022, 367, 120450.
DOI link

Protic imidazolium ionic liquids (PILs) have shown great potential as regents and catalysts in liquid-phase chemistry. However, their biological activity/toxicity and solvation properties are rather understudied compared to those of more common aprotic ionic liquids (APILs). In this work, for the first time, we studied the cytotoxicity of nine chemically relevant imidazolium PILs with various alkyl side chains in the cation and compared it with the cytotoxicity of the corresponding aprotic analogues. The experimental data were supported by computational modeling. The results suggested the type of anion to be the major factor governing the cytotoxicity of the studied ILs with short alkyl side chains. Of note, even low-toxic PILs imposed considerable deleterious effects on eukaryotic cells when used as cryopreservation agents. According to a scanning electron microscopy (SEM) study, due to the weak amphiphilic properties of imidazolium cations with short alkyl side chains, the studied IL/water mixtures tended to produce simple solid hydrates rather than complex liquid systems with microdomain organization.

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.
DOI link

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.
DOI link

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.

Sterically Hindered Quaternary Phosphonium Salts (QPSs): Antimicrobial Activity and Hemolytic and Cytotoxic Properties

Ermolaev V.V., Arkhipova D.M., Miluykov V.A., Lyubina A.P., Amerhanova S.K., Kulik N.V., Voloshina A.D., Ananikov V.P., Int. J. Mol. Sci., 2022, 23, 86.
DOI link

Structure–activity relationships are important for the design of biocides and sanitizers. During the spread of resistant strains of pathogenic microbes, insights into the correlation between structure and activity become especially significant. The most commonly used biocides are nitrogen-containing compounds; the phosphorus-containing ones have been studied to a lesser extent. In the present study, a broad range of sterically hindered quaternary phosphonium salts (QPSs) based on tri- tert-butylphosphine was tested for their activity against Gram-positive (Staphylococcus aureus, Bacillus cereus, Enterococcus faecalis) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria and fungi (Candida albicans, Trichophyton mentagrophytes var. gypseum). The cation structure was confirmed to determine their biological activity. A number of QPSs not only exhibit high activity against both Gram-positive and -negative bacteria but also possess antifungal properties. Additionally, the hemolytic and cytotoxic properties of QPSs were determined using blood and a normal liver cell line, respectively. The results show that tri-tert-butyl(n-dodecyl)phosphonium and tri-tert-butyl(n-tridecyl)phosphonium bromides exhibit both low cytotoxicity against normal human cells and high antimicrobial activity against bacteria, including methicillin-resistant strains S. aureus (MRSA). The mechanism of QPS action on microbes is discussed. Due to their high selectivity for pathogens, sterically hindered QPSs could serve as effective tunable biocides.

Towards Sustainable Carbon Return from Waste to Industry via C2-Type Molecular Unit

Rodygin K.S., Lotsman K.A., Samoylenko D.E., Kuznetsov V.M., Ananikov V.P., Int. J. Mol. Sci., 2022, 23, 11828.
DOI link

A general possibility of a sustainable cycle for carbon return to high-value-added products is discussed by turning wastes into acetylene. Pyrolyzed solid municipal wastes, pyrolyzed used cationic exchangers, and other waste carbon sources were studied in view of the design of a sustainable cycle for producing calcium carbide and acetylene. The yields of calcium carbide from carbon wastes were as high as those from industrial fossil raw materials (coke, charcoal, etc.). Conversion of carbon-containing wastes to calcium carbide provides an excellent opportunity to make acetylene, which is directly compatible with modern industry. Overall, the process returns carbon-containing wastes back to sustainable cycles to produce high-value-added products involving only C2 -type molecules (calcium carbide and acetylene). Calcium carbide may be stored and transported, and on-demand acetylene generation is easy to realize. Upon incorporation into the waste processing route, calcium carbide may be an efficient carbon reservoir for quick industrial uptake.

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.
DOI link

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.

Automated Recognition of Nanoparticles in Electron Microscopy Images of Nanoscale Palladium Catalysts

Boiko D.A., Sulimova V.V., Kurbakov M.Yu., Kopylov A.V., Seredin O.S., Cherepanova V.A., Pentsak E.O., Ananikov V.P. , Nanomaterials, 2022, 12, 3914.
DOI link

Automated computational analysis of nanoparticles is the key approach urgently required to achieve further progress in catalysis, the development of new nanoscale materials, and applications. Analysis of nanoscale objects on the surface relies heavily on scanning electron microscopy (SEM) as the experimental analytic method, allowing direct observation of nanoscale structures and morphology. One of the important examples of such objects is palladium on carbon catalysts, allowing access to various chemical reactions in laboratories and industry. SEM images of Pd/C catalysts show a large number of nanoparticles that are usually analyzed manually. Manual analysis of a statistically significant number of nanoparticles is a tedious and highly time-consuming task that is impossible to perform in a reasonable amount of time for practically needed large amounts of samples. This work provides a comprehensive comparison of various computer vision methods for the detection of metal nanoparticles. In addition, multiple new types of data representations were developed, and their applicability in practice was assessed.

Optimal balance in the catalyst dynamics enables C(2)–Harylation of (benz)imidazoles and (benz)oxazoles by an insitugenerated Ni/NHC system

Khazipov O.V., Shepelenko K.E., Soliev S.B., Nikolaeva K.A., Chernyshev V.M., Ananikov V. P., ChemCatChem, 2022, e202201055.
DOI link

An efficient method for the C(2)-H arylation of (benz)imidazoles and (benz)oxazoles with aryl chlorides and aryl bromides under Ni/NHC catalysis has been developed. The main benefit of the method is the in situ generation of active Ni/NHC complexes from the air-tolerant bench-stable precursors NiCl2Py2, IMesHCl, and potassium tert-butoxide, which plays a dual role as base and Ni(II) to Ni(0) reductant. The approach represents a userfriendly alternative for procedures relying on the use of toxic phosphine ligands or unstable air-sensitive Ni(cod)2. The concept highlighted in the present study shows that mapping a competitive picture of catalyst dynamics and revealing the competitive processes towards the destruction and stabilization of catalytically active species enables a highly efficient catalytic system to be built under simple conditions.

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.
DOI link

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.

Yellow to blue switching of fluorescence by the tuning of the pentaphenylphosphole structure: phosphorus electronic state vs. ring conjugation

Shaydullin R.R., Galushko A.S., Pentsak E.O., Korshunov V.M., Taydakov I.V., Gordeev E.G., Minyaev M.V., Nasyrova D.I., Ananikov V. P. , Phys. Chem. Chem. Phys., 2022, 24, 25307-25315.
DOI link

The interaction between diphenylacetylene and dichlorophenylphosphine under various conditions is a simple method for the preparation of pentaphenylphosphole derivatives exhibiting fluorescence properties. Depending on the electronic state of the various centers of the phospholic structure, it was possible to obtain molecules with fluorescence, as in the blue area for 1,2,3,4,5-pentaphenyl-2,5-dihydro-phosphole-1-oxide (H 2PPPO), in the yellow area for 1,2,3,4,5-pentaphenylphosphole-1-oxide (PPPO) and in the cyan area for 1,2,3,4,5-pentaphenylphosphole (PPP). The effect of the structure and π-conjugation on the optical properties of these compounds was studied using PPP derivatives as examples. Unusual changes in the optical properties of PPP derivatives in solution and in the crystalline state are explained. In the case of agglomeration of PPPO and PPP molecules, the effect of aggregation-induced emission (AIE) was observed to have weak fluorescence in solution and strong fluorescence in the aggregated state. However, for H2PPPO, the AIE effect remains mild. With the help of experimental studies, supported by theoretical calculations, the main mechanism of the optical properties of pentaphenylphosphole derivatives has been revealed. It was observed that the intramolecular motions of PPPO and PPP are more limited in the solid state than the motions of H2PPPO, which is associated with less conjugation of the phenyl rotors of H2PPPO. The analysis of the structure and distribution of electron density showed why hydrogenation of the phosphole ring leads to a sharp change in the optical properties of pentaphenylphosphole derivatives, while the oxidation of phosphorus does not lead to the disappearance of the AIE effect and to a lesser extent affects the change in the fluorescence wavelength. Thus, it was shown how the regulation of various structural features of the phospholic ring helps to control the optical properties of such compounds.

Atom-economic approach to the synthesis of α-(hetero)aryl substituted furan derivatives from biomass

Romashov L.V., Kozlov K.S., Skorobogatko M.K., Kostyukovich A.Yu., Ananikov V.P., Chem. Asian J., 2022, e202101227.
DOI link

An atom-economic ring construction approach to the synthesis of α-(hetero)arylfurans based on renewable furanic platform chemicals has been developed. Corresponding compounds have been prepared in good to excellent yields via [2+2+2] and [4+2] cycloaddition reactions using metal-catalyzed or photoredox protocols. Easily available HMF-based 2-hydroxymethyl-5-ethynylfuran and 2-hydroxymethyl-5-cyanofuran were used as starting materials. A synthetic route with an improved carbon economy factor has been implemented to achieve sustainability aim. The possible application of arylfurans as molecular conductors has been investigated by DFT calculations, which revealed excellent charge transfer properties. As a future perspective, integration of biomass processing strategy into manufacturing of molecular electronics was pointed out to achieve the aim of sustainability.

Synthesis and characterization of Pd/NHCF complexes with fluorinated aryl groups

Prima D.O., Pankov R.O., Kostyukovich A. Yu., Minyaev M.E., Burykina J.V., Ananikov V.P., Dalton Trans., 2022, 51, 9843-9856.
DOI link

The key problem of the instability of fluorine-containing diazadienes was addressed to perform the efficient synthesis of imidazolium salts containing fluorine substituents in the aryl groups. The subsequent reaction of fluorine-containing imidazolium compounds (NHC F) with palladium salts under simple conditions afforded new Pd/NHCF complexes. Computational and structural studies were performed to assess the effect of fluorine on the Pd–NHC bond and gave insight into the electronic effects in the molecule. The introduction of fluorine substituents into the aryl rings of the NHC ligands leads to a slight decrease in their σ-donor properties. At the same time, there is a slight increase in the π-acceptor capacity of NHCF. These two effects compensate for each other, so that the Pd–NHC bonding energy remains virtually unchanged. Another observed effect is associated with a slight weakening of the trans influence of the NHCF ligands, which is expressed in the strengthening of the Pd–Solv bond in (NHC)Pd(Solv) complexes. For the first time, a series of novel Pd/NHCF complexes were synthesized via a straightforward approach from fluorine-containing anilines.

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.
DOI link

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.

Discovery of the N–NHC Coupling Process under the Conditions of Pd/NHC- and Ni/NHC-Catalyzed Buchwald–Hartwig Amination

Chernyshev V.M., Khazipov O.V., Shevchenko M.A., Pasyukov D.V., Burykina Ju.V., Minyaev M.E., Eremin D.B., Ananikov V.P., Organometallics, 2022, 41, 1519-1531.
DOI link

Complexes of palladium and nickel with N-heterocyclic carbene ligands (M/NHC, M = Pd, Ni) are widely used as effective catalysts for various amination reactions. A previously unaddressed transformation of M/NHC complexes under typical conditions of the Buchwald–Hartwig amination is disclosed. MII/NHC complexes react with primary aromatic and aliphatic amines in the presence of strong bases to give azol-2(5)-imines and M(0) species via a reductive elimination of NHC and azanide (N-deprotonated amine) ligands. Depending on the structures of the NHC and azanide, the N–NHC coupling can make a significant contribution to the M/NHC catalyst decomposition in the Buchwald–Hartwig and other amination reactions conducted in the presence of strong bases. The discovery of the N–NHC coupling reaction has been shown to be critically influenced by the steric bulkiness of N-substituents on the NHC ligand. The high steric bulkiness of the NHC is an important factor in suppressing the N–NHC coupling deactivation pathway.

Acetylene and ethylene – universal C2 molecular units in cycloaddition reactions

Ledovskaya M.S., Voronin V.V., Rodygin K.S., Ananikov V.P., Synthesis, 2022, 54, 999-1042.
DOI link

Acetylene and ethylene are the smallest molecules that contain an unsaturated carbon-carbon bond and can be efficiently utilized in a large variety of cycloaddition reactions. In the present review, we summarize the application of these C2 molecular units in cycloaddition chemistry and highlight their amazing synthetic opportunities.

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.
DOI link

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.

A novel approach to study catalytic reactions via electrophoretic NMR on the example of Pd/NHC-catalyzed Mizoroki–Heck cross-coupling reaction

Kulikovskaya N.S., Denisova E.A., Ananikov V.P., Magn Reson Chem, 2022, 60, 954-962.
DOI link

Investigation of catalytic reactions using nuclear magnetic resonance (NMR) is a crucial task, which is often challenging to perform due to rather complex transformations at the metal center. In this work, it was shown that electrophoretic NMR can be a suitable method for studying catalytic reactions and for observing the changes in the catalyst nature. As an important example involving palladium catalysts with N-heterocyclic carbine ligands (NHCs), the breakage of the Pd-NHC bond can occur during the catalytic process. Electrophoretic NMR allows the distinction of compounds in the spectra depending on the charge, thus bringing new opportunities to mechanistic studies. Here, we present independent evidence of R-NHC product formation in the Pd-catalyzed Mizoroki–Heck reaction—the key process for catalyst change from the molecular to nano-scale type.