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New antioxidants are commonly evaluated via two main approaches, i.e., the ability to donate an electron and the ability to intercept free radicals. We compared these approaches by evaluating the properties of 11 compounds containing both antioxidant moieties (mono- and polyphenols) and auxiliary pharmacophores (pyrrolidone and caprolactam). Several common antioxidants, such as butylated hydroxytoluene (BHT), 2,3,5-trimethylphenol (TMP), quercetin, and dihydroquercetin, were added for comparison. The antioxidant properties of these compounds were determined by their rates of reaction with 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and their oxidation potentials from cyclic voltammetry. Although these methods test different chemical properties, their results correlate reasonably well. However, several exceptions exist where the two methods give opposite predictions! One of them is the different behavior of mono- and polyphenols: polyphenols can react with DPPH more than an order of magnitude faster than monophenols of a similar oxidation potential. The second exception stems from the size of a "bystander" lactam ring at the benzylic position. Although the phenols with a seven-membered lactam ring are harder to oxidize, the sterically nonhindered compounds react with DPPH about 2× faster than the analogous five-membered lactams. The limitations of computational methods, especially those based on a single parameter, are also evaluated and discussed.

International audience; Primary products of single-electron transfer to/from organogermanium compounds (anion radicals and cation radicals issued from reduction and oxidation, respectively) and their chemistry are considered through different approaches to the generation and study of organogermanium ion radicals; the relationship between the data obtained by various methods, including voltammetry, UV-Vis and photoelectron spectroscopy, and the possibilities of modern computational methods in this field are discussed. The chapter provides a systematized overview of literature data on the ion radicals of tetravalent organogermanium compounds, including germanium catenates, low-valent (germylenes, digermenes, phosphagermene) and hypercoordinated germanium derivatives, including germatranes. General aspects of the ion radical chemistry of organogermanium compounds, as well as its premise for the actively developing area of germylene catalysis in organic and organoelement synthesis are considered along with the possible prospects for the development of this field. © 2023 John Wiley and Sons, Inc. All rights reserved.

Tin coordination derivatives are notable for the availability of obtaining, safety in use and high stability. Together with their useful properties, this determines the prospects for their use in medicine...

International audience; For the first time, the possibility of obtaining porous germanium from both single-crystal and polycrystalline starting materials using environmentally friendly (in contrast to the commonly used HF and HCl) imidazolium ionic liquids (IL) was shown. It was demonstrated that pore formation depended significantly on the viscosity of the IL, on the etching current density and etching time, and on defects and imperfections of the substrate surface. By varying these parameters, the rates of two competing processes - formation and growth of pores and electropolishing - could be adjusted, consequently allowing germanium with a various structured surface, including a porous surface. In particular, using a more viscous IL (for example, [BMIM][PF6] versus [BMIM][BF4]) made it possible to reduce the rate of dissolution of the germanium dioxide surface layer; as a result, the formation and growth of pores became a dominant process. At the same time, the dissolution rate of the already formed porous layer (electropolishing) increased with the etching current density and the number of defects and imperfections of the germanium surface.

A complex between SiCl2 and CO of the 1:1 composition with coordination of the silylene to the C atom of carbon monoxide is detected in Ar matrices using FTIR spectroscopy. A positive shift of the ν(CO) band of the complex relative to the corresponding band of free CO and a theoretical analysis of the nature of the complex indicate that it is a nonclassical carbonyl complex. It is the first experimentally detected nonclassical carbonyl complex of any silylenes. The main direction of photoinduced transformations of the complex is its decomposition into the starting reactants. The potential energy surface of the SiCl2 + CO system was explored theoretically. It is shown that further thermal transformations of the primary complex are energetically unfavorable.

A 1: 1 photostable complex between dichlorosilylene and CO2 was detected using matrix-isolation FTIR spectroscopy. The photostability can be attributed to the existence of photochemical equilibria between this complex and products of its isomerization, first of all, a complex of dichlorosilanone with CO, which are strongly shifted to the complex. A detailed computational study of the potential energy surface of the SiCl2 + CO2 system was carried out.

The concept of using redox-active ligands, which has become extremely widespread in organometallic chemistry, is often considered from ‘their effect on the metal center properties’ point of view and ‘how to modify the ligands’. In this paper, we present the reverse side of this effective approach – a dramatic change of redox properties of ligands under the influence of a redox-inert metal. Germanium derivatives based on 2,3-dihydroxynaphthalene (1) and N,N′-bidentate ligands, namely 2,2′-bipyridine (2) and 1,10-phenanthroline (3), were obtained and characterized by CV, UV-vis spectroscopy, DFT calculations and in the case of 3 X-ray diffraction. It was shown that the HOMO of the complexes is almost completely located on the naphthalene fragment while the LUMO is on the N,N-ligands. At the same time, there are no boundary molecular orbitals on the germanium atom, but it forms the axial part of the molecule holding two opposite motifs together. Moreover, it sharply affects the level of HOMO and LUMO. Derivatives 2 and 3 are more easily oxidized compared to 2,3-dihydroxynaphthalene by 0.31–0.34 V (7–8 kcal mol−1) and are more easily reduced compared to N,N-donors by 1.08–1.15 V (25–26.5 kcal mol−1). All this together makes it possible to form a system with a narrow HOMO/LUMO gap (∼2 eV). The crystal structure of 3 consists of alternating monomolecular easily oxidizing and easily reducing layers formed due to intermolecular interactions, in particular π-stacking. In addition, in contrast to 1 that starts to decompose noticeably at the temperatures from 200 °C, 2 and 3 have an extremely high thermal stability. They remain stable with no signs of decomposition and melting up to 400 °С. We believe that this approach to the formation of the supramolecular structure may present prospects for obtaining new functional materials.

New Schiff base germanate derivative containing the chain Ar–C=N→Ge←N=C–Ar was synthesized and characterized by physical methods including X-ray diffraction. The stability of the corresponding radical anion obtained electrochemically was confirmed by cyclic voltammetry, the results were compared with UV-VIS data and quantum chemical calculations.

International audience; Anodic etching of n-type {111} silicon in ionic liquid (IL) systems ([RMIM] [X], R = H, Bu; X = BF4-, PF6-), realized under galvanostatic conditions and at room temperature, allowed the formation of porous silicon surfaces with different pore morphology depending on the etching time, current density, and the IL used. The study of the effect of water content in IL on the etching process has shown a water content of 1% to be optimal. The role of the anion on the etching process was elucidated using 1-methylimidazolium tetrafluoroborate ([HMIM][BF4]) and 1-methylimidazolium hexafluorophosphate ([HMIM] [PF6]) IL systems. [HMIM] [BF4] was found to be most efficient for the formation of a silicon nanostructured array with a pore size of 30-80 nm. The thusprepared porous silicon samples show fluorescence in blue light (475 nm). The NMR spectra of [HMIM] [BF4] ionic liquid before and after etching do not show noticeable changes, which makes it possible to consider this IL as a potentially recyclable etching agent.

International audience; Various forms of germanium and germanium-containing compounds and materials are actively investigated as energy-intensive alternatives to graphite as the anode of lithium-ion batteries. The most accessible form-germanium dioxide-has the structure of a 3D polymer, which accounts for its rapid destruction during cycling, and requires the development of further approaches to the production of nanomaterials and various composites based on it. For the first time, we propose here the strategy of using 2-carboxyethylgermanium sesquioxide ([O GeCH CH CO H] , 2-CEGS), in lieu of GeO , as a promising, energy-intensive, and stable new source system for building lithium-ion anodes. Due to the presence of the organic substituent, the formed polymer has a 1D or a 2D space organization, which facilitates the reversible penetration of lithium into its structure. 2-CEGS is common and commercially available, completely safe and non-toxic, insoluble in organic solvents (which is important for battery use) but soluble in water (which is convenient for manufacturing diverse materials from it). This paper reports the preparation of micro- (flower-shaped agglomerates of ≈1 μm thick plates) and nanoformed (needle-shaped nanoparticles of ≈500×(50-80) nm) 2-CEGS using methods commonly available in laboratories and industry such as vacuum and freeze-drying of aqueous solutions of 2-CEGS. Lithium half-cell anodes based on 2-CEGS show a capacity of ≈400 mAh g for microforms and up to ≈700 mAh g for nanoforms, which is almost two times higher than the maximal theoretical capacity of graphite. These anodes are stable during the cycling at various rates. The results of DFT simulations suggest that Li atoms form the stable Li O with the oxygen atoms of 2-CEGS, and actual charge-discharge cycles involve deoxygenated GeC H molecules. Thus, C chains loosen the anode structure compared to pure Ge, improving its ability to accommodate Li ions.

The electroreduction (ER) of benzo[a]phenazine-7,12-dioxide (1) and 2-ethoxycarbonyl-3-methyl-quinoxaline-1,4-dioxide (2) in DMF on a glassy carbon electrode is studied by the methods of cyclic voltammetry, chronoamperometry, and electrolysis at controlled potential. In aprotic medium, these compounds are reduced to form relatively stable complexes as observed in both cyclic voltammetry curves and UV spectra. The deoxygenation of the derivatives of phenazine and quinoxaline N,N′-dioxides proceeds as a result of decomposition of the radical formed either at the ER of complexes of these compounds with СН3СООН or as a result of protonation of radical anions. For compound 2, the competition between the reactions of decomposition and ER of this radical is observed.

International audience; In this paper, we propose a halogen-free process for the preparation of germanium micro-scale particles with a nano-structured surface morphology from germanium citrate, an easily accessible and environment-friendly precursor formed from germanium dioxide and citric acid in an aqueous medium. Electrodeposition of nanostructured Ge anodes on copper foil was performed via electrolysis of 1-5% germanium citrate solution in propylene glycol with addition of 5% acetic acid. Cyclic voltammetry data suggested that germanium citrate is an electrochemically inactive compound, but readily undergoes reduction by cathodic hydrogen released in the electrolysis. Such behaviour allows one to run the electrolysis under simple galvanostatic conditions without any need for controlling the potential. Furthermore, no diaphragm is required to separate the cathodic and anodic cell compartments. The electrodeposition produces black and compact films composed of similar to 200 nm germanium particles, which, in turn, consist of nanoparticles no larger than 25 nm in size (SEM and TEM data). XRD and Raman spectroscopy data lead to the conclusion that germanium precipitates in the amorphous phase; however, with an increase in the power of the He-Ne laser (632.8 nm) during Raman spectra recording, it transforms into a nanocrystalline form. Testing germanium anodes in lithium-ion half-cells showed a specific capacity of similar to 600 mA h g(-1) at 1-2C current rates, which is comparable to the best results achieved for Ge anodes produced using more sophisticated and less environment-friendly techniques.

Electrochemical reduction of ortho-piperidino substituted nitro(het)arenes in an undivided cell on a lead cathode in 8% HCl gave either 1,2,3,4-tetrahydropyrido[1,2-a]-benzimidazoles or 6,7,8,9-tetrahydropyrido[3′,2′:4,5]- imidazo[1,2-a]pyridines. The reductive heterocyclization mechanism involves the initial formation of a nitroso derivative followed by the formation of an imidazole ring.

The concept of using redox-active ligands, which has become extremely widespread in organometallic chemistry, is often considered from 'their effect on the metal center properties' point of view and 'how to modify the ligands'. In this paper, we present the reverse side of this effective approach - a dramatic change of redox properties of ligands under the influence of a redox-inert metal. Germanium derivatives based on 2,3-dihydroxynaphthalene (1) and

Spin-labeled cyrhetrenes [(NNCp)Re(CO)3] and [(INCp)Re(CO)3], where NNCp is nitronyl nitroxide 2-(η5-cyclopentadienyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl and INCp is the corresponding imino nitroxide, were synthesized and characterized by EPR, CV, XRD, magnetochemistry and quantum chemistry methods. The correlations between different arrangements of paramagnetic centers and the magnetic exchange interactions for three polymorphs of [(NNCp)Re(CO)3] were studied. It was concluded that high kinetic stability of nitroxide-substituted cyrhetrenes is a promising feature of compounds for the creation of multifunctional contrast agents.

New monomeric O,N-heterocyclic germylene AdAPGe (1) based on 4,6-di-tert-butyl-N-adamantyl-o-aminophenol is synthesized and structurally characterized. Germylene 1 in the crystal demonstrates weak Ge⋯Ge interactions between adjacent molecules. The redox activity of compound 1 and its known analogs PhAPGe (2), t-BuAPGe (3) was studied using cyclic voltammetry and chemical oxidation by the phenoxy radical. Germylene 1, as opposed to 2 and 3, was found to form a relatively stable o-iminosemiquinonate moiety during oxidation. The last one was detected by EPR spectroscopy in toluene solution at low temperatures. The catalytic activity of germylenes 1–3 and dippAPGe (4) (dipp – 2,6-di-isopropylphenyl) towards hydroboration and cyanosilylation of benzaldehyde was examined. Germylene 1 demonstrates the most potent promoter properties for such reactions, which allowed cyanosilylation and hydroboration of aldehyde under mild conditions with excellent conversion quickly. Theoretical studies were performed to establish the mechanism, and different reaction routes were examined. According to the DFT (B3LYP/def2-SVP) calculation, cyanosilylation and hydroboration processes are initiated by coordinating TMSCN or HBpin with the catalyst. The followed reaction with aldehyde leads to the resulting products.

International audience; Bis-phenyl derivative of a novel family of bis-metallatranes, 1,1'-diphenyl-bis-germatrane, was synthesized and characterized. One-electron oxidation of this compound is electrochemically and chemically reversible providing a persistent radical cation.

We have discovered synthetic access to β-hydroperoxy-β-peroxylactones via BF3-catalyzed cyclizations of a variety of acyclic precursors, β-ketoesters and their silyl enol ethers, alkyl enol ethers, enol acetates, and cyclic acetals, with H2O2. Strikingly, independent of the choice of starting material, these reactions converge at the same β-hydroperoxy-β-peroxylactone products, i.e., the peroxy analogues of the previously elusive cyclic Criegee intermediate of the Baeyer–Villiger reaction. Computed thermodynamic parameters for the formation of the β-hydroperoxy-β-peroxylactones from silyl enol ethers, enol acetates, and cyclic acetals confirm that the β-peroxylactones indeed correspond to a deep energy minimum that connects a variety of the interconverting oxygen-rich species at this combined potential energy surface. The target β-hydroperoxy-β-peroxylactones were synthesized from β-ketoesters, and their silyl enol ethers, alkyl enol ethers, enol acetates, and cyclic acetals were obtained in 30–96% yields...

Covalent immobilization of fluoride-encapsulating octaphenyl silsesquioxane F−@Ph8T8 on glassy carbon (GC) was achieved using a new ambifunctional grafting agent, iodomethyltrimethylsilane TMSCH2I. This grafting method did not require any pre-grafting functionalization of the Ph-trimmed substrate; instead, the GC interface was anodically covered with CH2I groups whose ensuing reduction in the presence of F−@Ph8T8 resulted in the covalent grafting of the phenyl silsesquioxane cage onto the GC surface via the CH2 linker(s). The resulting ionic interface can be used to detect exposure to Li+- and H+-containing media. The proposed electrochemical process offers a general method for covalent binding of two (poly)aromatic substrates by a methylene bridge. Keywords: Glassy carbon, Functionalization, Fluoride encapsulating, Silsesquioxane, Sensing

Twenty six peroxides belonging to bridged 1,2,4,5-tetraoxanes, bridged 1,2,4-trioxolanes (ozonides), and tricyclic monoperoxides were evaluated for their in vitro antimalarial activity against Plasmodium falciparum (3D7) and for their cytotoxic activities against immortalized human normal fibroblast (CCD19Lu), liver (LO2), and lung (BEAS-2B) cell lines as well as human liver (HepG2) and lung (A549) cancer-cell lines. Synthetic ozonides were shown to have the highest cytotoxicity on HepG2 (IC50=0.19–0.59 μm), and some of these compounds selectively targeted liver cancer (selectivity index values for compounds 13 a and 14 a are 20 and 28, respectively) at levels that, in some cases, were higher than those of paclitaxel, artemisinin, and artesunic acid. In contrast some ozonides showed only moderate antimalarial activity against the chloroquine-sensitive 3D7 strain of P. falciparum (IC50 from 2.76 to 24.2 μm; 12 b, IC50=2.76 μm; 13 a, IC50=20.14 μm; 14 a, IC50=6.32 μm). These results suggest that these derivatives have divergent mechanisms of action against cancer cells and malaria-infected cells. A cyclic voltammetry study of the peroxides was performed, but most of the compounds did not show direct correlation in oxidative capacity–activity. Our findings offer a new source of antimalarial and anticancer agents through structural modification of peroxide compounds.

Oxidative coupling of oxime and β-dicarbonyl compounds dominates in a β-dicarbonyl compound/oxime/Cu(II)/t-BuOOH system; in the absence of oxime, oxidative coupling of t-BuOOH and a β-dicarbonyl compound (Kharasch peroxidation) takes place. The proposed conditions for oxidative coupling of oximes with dicarbonyl compounds require only catalytic amounts of copper salt and t-BuOOH serves as a terminal oxidant. The C–O coupling reaction proceeds via the formation of tert-butoxyl, tert-butylperoxyl and iminoxyl radicals. Apparently, tert-butylperoxyl radicals oxidize oxime into iminoxyl radical faster than they react with β-dicarbonyl compounds forming the Kharasch peroxidation product. Iminoxyl radicals are responsible for the formation of the target C–O coupling products; the yields are up to 77%.

Reduction of 1,1′-(4,6-dinitro-1,3-phenylene)dipyridinium dichloride with SnCl2 afforded dipyrido[1,2-a:1′,2′-a′]benzo[1,2-d:5,4-d]diimidazole which was converted into the corresponding quinone-type 6,13-dione in three simple steps.

A variety of vinyl sulfones were prepared from alkenes and sulfonyl hydrazides via electrochemical oxidative sulfonylation. The reaction proceeds in an experimentally convenient undivided electrochemical cell equipped with graphite and iron electrodes employing KI as a redox catalyst and a supporting electrolyte. Applying extremely high current density up to 270 mA/cm 2 permits rapid synthesis in a compact reactor and with small surface area electrodes. A possible reaction mechanism was proposed with the use of cyclic voltammetry. It is the combination of anodic and cathodic processes in this reaction that makes it possible to obtain products under mild conditions with yields from moderate to high.

In continuation of our previous studies on N-(4-nitrophenyl)hydroxylamine ( 1 ), we investigated the electroreduction of N-(2- ( 2 ) and N-(3-nitrophenyl)hydroxylamines ( 3 ) in N,N-dimethylformamide/Bu 4 NClO 4 , using chronoamperometry, cyclic voltammetry, digital simulation and quantum chemical calculations. It was shown that anion radical 3 is rather stable and does not eliminate a hydroxide anion, unlike 2 whose electroreduction mechanism is similar to that previously observed for 1 . At the same time, the elimination reaction is observed for dianion of 3 formed at potentials of the first electron transfer by disproportionation of anion radicals. Results of quantum-chemical calculations show that the high stability of anion radical 3 results from the absence of unpaired electron density on its hydroxylamine group.

The influence of solvent (DMF, MeCN, and water) and R1, R2 substituent nature on the formal oxidation potential (E°´) of 4-R1,R2-2,2,6,6-tetramethylpiperidine 1-oxyls (1a—f) on a glass carbon electrode was studied by cyclic voltammetry. It was shown that for all the solvents the observed dependence had the form E°´ = ρ″σ″ + b, where σ″ is the substituent constant. The b values decreased with an increase of the solvent solvating ability, while the values ρ″ are similar for all the solvents, surpassing the corresponding values for nitroxyls of the imidazoline series with substituents at position 3, which can be interpreted as an abnormally strong influence of the substituent remote from the reaction center in 1a—f. The experimental values E°´ were linearly correlated with the reaction free energy values (ΔG) calculated by DFT B3LYP and MP2 for the gas phase contribution and by HF/PCM for the contribution of solvation effects. When applying the B3LYP and the HF/PCM approaches in combination, the dependence of E°´ on ΔG for all the considered solvents was described by a linear correlation equation with a slope close to unity and a constant term which was close to the theoretical value of the absolute potential of the reference electrode used.

The electroreduction of N-(3-nitrophenyl)hydroxylamine in DMF was studied using cyclic voltammetry, chronoamperometry, and numerical simulation. It is shown that the stability of formed radical anion is significantly higher than that of the radical anion of the 4-nitrophenyl derivative. In the range of low concentrations and high potential scan rates, the electroreduction of N-(3-nitrophenyl)hydroxylamine is complicated only by the formation of complexes between the depolarizer molecules, most likely, due to hydrogen bonds, as well as between the depolarizer and its radical anion. The thermodynamic and kinetic parameters of these processes were evaluated.

The many applications of photon upconversion-conversion of low-energy photons into high-energy photons-raises the question of the possibility of "electron upconversion". In this Review, we illustrate how the reduction potential can be increased by using the free energy of exergonic chemical reactions. Electron (reductant) upconversion can produce up to 20-25 kcal mol-1 of additional redox potential, thus creating powerful reductants under mild conditions. We will present the two common types of electron-upconverting systems-dissociative (based on unimolecular fragmentations) and associative (based on the bimolecular formation of three-electron bonds). The possible utility of reductant upconversion encompasses redox chain reactions in electrocatalytic processes, photoredox cascades, design of peroxide-based medicines, firefly luminescence, and reductive repair of DNA photodamage.

International audience; Complexes of tetra‐ and hexa‐coordinated germanium AdrCat2Ge (1, AdrCat = adrenaline catecholate), AldCat2Ge (2, AldCat = 4‐formylcatecholate), AldCat3Ge(Et3NH)2 (3) were synthesized by the reaction of germanium dioxide with adrenaline and 3,4‐dihydroxybenzaldehyde in aqueous solution. The structures of the complexes were confirmed by 1H and 13C NMR and IR spectroscopy, HRMS, and elemental analysis. Cyclic voltammetry in phosphate buffer solutions (pH = 6.86) has shown the oxidation potentials Ep of these complexes to be shifted by ca. 330–360 mV to more positive potentials compared to the parent aromatic diols, which means that their electron‐releasing properties were diminished by about 7.6–8.3 kcal mol–1. A study of the kinetics of the reaction of these complexes with 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) free radical in the presence of 5 % acetonitrile reveals a decrease of approximately one order of magnitude in the radical scavenging activity of adrenaline and model 3,4‐dihydroxybenzaldehyde upon their complexation with Ge. The corresponding rate constants drop from (3.23 ± 0.07) × 103 L mol–1 s–1 (adrenaline) to (3.80 ± 0.20) × 102 L mol–1 s–1 for 1, and from (4.40 ± 0.20) × 103 L mol–1 s–1 (3,4‐dihydroxybenzaldehyde) to (4.45 ± 0.25) × 102 L mol–1 s–1 for 2 and 3 (germanium is equally capable to bind two or three molecules of the diol). Keeping in mind that 1,2‐diols are widespread in the living nature and often have important biological functions, these results will contribute to the understanding of role of germanium dioxide in metabolic mechanisms and to alert against unreasonable use of Ge preparations.

The green conversion of germanium dioxide into soluble non-halogenated forms suitable for further processing occurs smoothly and in high yields under the action of 3,5-di-tert-butylbenzene-1,2-diol in presence of biologically active N-donor ligands L. The formed hexacoordinated germanium catecholate complexes (DTBCat)2GeL2 (DTBCat = 3,5-di-tert-butylcatecholate, L = nicotinic acid, nicotinamide and isoniazid) 1–3 are air stable and soluble in common organic solvents. These new complexes are easily reducible at a glassy carbon electrode in DMF/0.1 M Bu4NBF4 at the cathodic potentials remarkably less negative than those of the reduction of parent non-coordinated N-donor ligands L; the corresponding anodic shifts for 1–3 are 0.598, 1.009 and 0.978 V, respectively. The ease of the electrochemical reduction and the energy of electron donation from the ligands L to germanium in 1–3 are in good agreement with DFT B3LYP/def2tzvp analysis and the stabilization energies of these germanium complexes.

Synthetic ozonides and tetraoxanes were shown to have high cytotoxicity in vitro when tested on androgen-independent prostate cancer cell lines DU145 and PC3, which is in some cases was higher than that of doxorubicin, cisplatin, etoposide, artemisinin, and artesunate. Activity of ozonide stereoisomers differs from each other. This difference in activity and absence of correlation between activity of stereoisomers and their oxidative properties allow us to suggest existence of a quite specific mechanism of cytotoxicity of these endoperoxides different from a traditional mechanism based mainly on oxidative properties of peroxides.

Сyclic voltammetry, chronoamperometry, coulometry, electrolysis, digital simulation, quantum chemical calculations of 9-fluorenol as an example, were used to show that the electroreduction of aryl derivatives of methanol in 0.1 M Bu4NClO4/DMF proceeds via the ECE mechanism (including the stages of radical anion formation and the C OH bond cleavage in the radical anion) complicated by the reactions of the depolarizer with the anionic products. Among these reactions are the deprotonation of 9-fluorenol and its monoanions by hydroxide anion and fluorenyl anion. The thermodynamic parameters of the reactions have been estimated both theoretically and experimentally. It was found that the equilibrium constants of the fluorenyl anions deprotonation are close (C-anion) or higher (O-anion) than that of fluorenol. As a result the total equilibrium is shifted towards the side of the dianion of 9-fluorenone. The unusual ratio of the equilibrium constants was explained by lower basicity of π*-dianion compare with other anions.

Copper(I) halides were used as mediators in the synthesis of β-hydroxysulfones via the oxysulfonylation of styrenes using sulfonylhydrazides. The feature of the developed process lies in the combination of a copper(I) salt with oxygen—the stoichiometric oxidant. Copper(II) species are responsible for the oxidation of sulfonylhydrazides, they are generated in small amounts in the O2/Cu(I)/Cu(II) redox system, which is formed during the reaction. The combination of these three components enables one to obtain in the case of α-methylstyrenes only β-hydroxysulfones and in the case of α-unsubstituted styrenes, β-hydroxysulfones as the main products and β-ketosulfones as the by-products. With good yields β-hydroxysulfones were prepared by reduction of the reaction mixture containing both products β-hydroxysulfones and β-ketosulfones with NaBH4. An electrochemical study revealed that the Cu(I)/Cu(II) pair can serve as an effective mediator of β-hydroxysulfones formation via redox processes.

Electrochemical reduction of N-(2-nitroaryl)pyridinium chlorides was accomplished in acidic aqueous alcoholic medium in the galvanostatic mode using tin, titanium, vanadium, and iron chlorides as redox-mediators. The use of SnCl2 as a mediator catalyst made it possible to shorten the electrosynthesis time as compared to the direct electroreduction on an electrode and prepare the intramolecular cyclization products, viz., substituted pyrido[1,2-a]benzimidazoles, in high yield. The influence of the mediator nature and its amount, current density, temperature, cathode material, medium acidity, and the substrate structure on the efficiency of reductive heterocyclization of N-(2-nitroaryl)pyridinium salts was studied.

Cyclic voltammetry, digital simulation and quantum chemical methods were applied to study the electroreduction mechanism of vicinal hydroxyl derivatives using 9H,9’H-bifluorene- 9,9’-diol as an example. Unlike the case of fluoren-9-ol, dissociation of the C9–C9’ bond rather than the C9–OH one occurs in radical anion of the substrate, similarly to that in radical cations formed upon oxidation of vicinal hydroxyl derivatives.

3,5-di-tert-Butylcatecholate (DTBC) germanium complexes (DTBC)2Ge[Py(CN)n]2 (n = 0…2) have been synthesized from GeO2, 3,5-di-tert-butylcatechol and cyano-substituted pyridines Py(CN)n and characterized by elemental analysis, NMR, IR and UV-VIS spectroscopy. The structure of 1 (with 4-cyanopyridine) has been determined by X-ray single crystal analysis. UV-VIS spectra have shown that these complexes are stable in CH3CN, toluene and CH2Cl2 solutions; in contrast, they are rapidly decomposed by dimethylformamide and tetrahydrofuran. Complexes 1 and 2 (with 4-cyano and 3-cyanopyridine) are electrochemically reducible in toluene/1 M Bu4NPF6 at E = -1.3…-1.7 V vs. AgCl. The quantum-chemical study of these complexes is in accordance with the unsuccessful attempts to obtain analogous derivatives with 2-cyanopyridine and 2,6-dicyanopyridine.

We have discovered synthetic access to β-hydroperoxy-β-peroxylactones via BF

International audience; The antioxidant activity of Ge-132 (2-carboxyethylgermanium sesquioxide, [(O0.5)3GeCH2CH2COOH]n), a widely used organic germanium dietary supplement, was assessed by cyclic voltammetry and through its interaction with a stable radical 2,2,-diphenyl-1-picrylhydrazyl (DPPH) monitored by UV-Vis and EPR spectroscopy in water, CH3CN, DMF, MeOH, and their mixtures with water. The results obtained by these methods are coherent in that Ge-132 can manifest its antioxidant activity only in the absence of water because the latter hydrolyses its Ge-O-Ge fragment responsible for quenching free radicals. Thus, contrary to a common use of Ge-132 as a water-soluble agent, it can act as an antioxidant solely in a lipid environment, which is important for understanding the mechanism of its biological activity.

International audience; 3,5-di-tert-Butylcatecholate (DTBC) germanium complexes (DTBC)2Ge[Py(CN)n]2 (n = 0…2) have been synthesized from GeO2, 3,5-di-tert-butylcatechol and cyano-substituted pyridines Py(CN)n and characterized by elemental analysis, NMR, IR and UV-VIS spectroscopy. The structure of 1 (with 4-cyanopyridine) has been determined by X-ray single crystal analysis. UV-VIS spectra have shown that these complexes are stable in CH3CN, toluene and CH2Cl2 solutions; in contrast, they are rapidly decomposed by dimethylformamide and tetrahydrofuran. Complexes 1 and 2 (with 4-cyano and 3-cyanopyridine) are electrochemically reducible in toluene/1 M Bu4NPF6 at E = -1.3…-1.7 V vs. AgCl. The quantum-chemical study of these complexes is in accordance with the unsuccessful attempts to obtain analogous derivatives with 2-cyanopyridine and 2,6-dicyanopyridine.