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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.

The invention and innovation of highly effective antimicrobials are always crucial tasks for medical and organic chemistry, especially at the current time, when there is a serious threat of shortages of effective antimicrobials following the pandemic. In the study presented in this article, we established a new approach to synthesizing three novel series of bioactive water-soluble tris-quaternary ammonium compounds using an optimized one-pot method, and we assessed their antimicrobial and antibiofilm potential. Five pathogenic microorganisms of the ESKAPE group, including highly resistant clinical isolates, were used as the test samples. Moreover, we highlighted the dependence of antibacterial activity from the hydrophilic–hydrophobic balance of the QACs and noted the significant performance of the desired products on biofilms with MBEC as low as 16 mg/L against bacteria and 8 mg/L against fungi. Particularly notable was the high activity against Pseudomonas aeruginosa and Acinetobacter baumannii, which are among the most resilient bacteria known. The presented work will provide useful insights for future research on the topic.

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.

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.

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.

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.

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.

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.

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.

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.