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Surface of boron-doped diamond film electrode was subjected to plasma-assisted electrochemical treatment by anodic plasma pulses, and a change in the rate constant of electron transfer for several model redox reactions was analyzed.

A simple strategy for the production of an efficient platinumfree electrocatalyst for the oxygen reduction reaction was demonstrated. Nitrogen-enriched carbon powder was synthesized by a solid-phase method consisting of grinding graphene oxide and melamine in a planetary ball mill without any solvents and high-temperature processing. Based on XPS and IR spectroscopy data, it was assumed that the high electrocatalytic activity of the obtained material is due to the presence of nitrogen atoms and quinone groups on its surface.

A new one-step method for the synthesis of an oxygen reduction electrocatalyst based on a nanocomposite of few-layer graphene structures and manganese oxides is proposed. It has been shown that by using the bipolar method of graphite exfoliation in the plasma electrolysis mode in solutions containing manganese salts, it is possible to obtain graphene nanostructures decorated with manganese oxides exhibiting high catalytic activity in the oxygen reduction reaction, which consists in a significant reduction in overpotential and an increase in the oxygen reduction current.

t—The potentialities of single-stage plasma-assisted electrochemical synthesis of few-layer graphene structures with high electrocatalytic characteristics toward the oxygen reduction reaction are demonstrated.

A simple method for the mechanochemical synthesis of an effective metal-free electrocatalyst for the oxygen reduction reaction was demonstrated. A nitrogen-doped carbon material was obtained by grinding a mixture of graphene oxide and melamine in a planetary ball mill. The resulting material was characterized by XPS, EPR, and Raman and IR spectroscopy. The nitrogen concentration on the N-bmGO surface was 5.5 at.%. The nitrogen-enriched graphene material (NbmGO has half-wave potential of −0.175/−0.09 V and was shown to possess high activity as an electrocatalyst for oxygen reduction reaction. The electrocatalytic activity of NbmGO can be associated with a high concentration of active sites for the adsorption of oxygen molecules on its surface. The high current retention (93% for 12 h) after continuous polarization demonstrates the excellent long-term stability of NbmGO.

A glassy carbon electrode is modified by generating cathodic and anodic electrolytic plasma near its surface. Voltage pulses of amplitude up to 250 V, pulse-on time of 10 ms, and rise time

Few-layer graphene structures synthesized by the plasma electrochemical method are used as modifiers of epoxy binders. It is shown that the obtained structures have the maximum positive effect on the strength characteristics of a cured epoxy–amine composition at a concentration of 0.2 wt %.

Physical and chemical characteristics of few-layer graphene structures (FLGS) obtained in various modes of electrochemical exfoliation of graphite have been studied. The FLGS synthesis was performe...

Redox reactions of cationic nitrosyl iron complexes with thiourea and its aliphatic derivatives have been studied using cyclic voltammetry technique and DFT investigation. Experimental values of the redox potentials have been determined and compared with results of DFT calculations. Using quantum-chemical modeling, structures of the forming reduced and oxidized forms have been obtained and their electronic structures have been studied. The redox processes in these systems were shown to be complicated and accompanied by the complexes decomposition. It is very important for understanding of their reactivity.

Isatin Schiff base ligands in combination with redox active metal ions have the potential to behave as non-innocent ligands facilitating industrially important chemical reactions. The ligand structure is easily modified by introducing substituents in three different positions, affecting the electron density distribution that was evaluated by Mulliken charge analysis and cyclic voltammetry for a range of isatin derivatives. It was noticed that coordination of these ligands to copper(II) bromide in alcohol resulted in copper reduction to Cu(I) species and alcohol oxidation. Compared to organic chemistry, the inorganic chemistry of these ligands remains poorly examined. Here, we present the structural study of sixteen novel copper complexes with mononuclear [Cu(L)2]Hal2/1 and halo-bridged binuclear [Cu2(μ-Hal)2(L)2] structures (L = isatin Schiff base ligand; Hal = Cl, Br and I). Finally, application of the above complexes for alcohol oxidation was evaluated: the complexes selectively catalyse benzyl alcohol oxidation to the corresponding aldehyde with almost quantitative yields and high selectivity.

A comparative study of electrochemical characteristics of graphite electrodes and precipitates of suspensions produced by the graphite exfoliation is carried out. The graphite is exfoliated into low-layered graphene structures formed in the course of electrochemical impact during the applying of alternating potential to the electrodes. The low-layered graphene structures and graphite electrodes were characterized using numerous procedures from optical, electron, and scanning microscopy, UV-vis-, IR-, Raman, and XPSspectroscopy, and thermogravimetric analysis. The rate constant of electron transfer at the initial graphite for [Ru(NH3)6]2+/3+ and [Fe(CN)6]4–/3– redox pairs is shown to approach the value measured both for the lowlayered graphene structures obtained during the graphite electrode exfoliation and for highly oriented carbon nanowalls and single-walled nanotubes measured earlier. At the same time, the Fe2+/3+ redox-process occurring at the graphite electrode is faster than at the low-layered graphene structures and much faster (by 2–3 orders of magnitude) than at the nanowalls. It is concluded that no significant acceleration of the electron transfer generally occurs when passing from the graphite electrodes to the low-layered graphene structures.

A glassy carbon (GC) electrode has been modified by 3–6 potential impulses of different polarity with amplitude up to 250 V, duration of 10 ms and pulse rise-time of

A graphene oxide aerogel (GOA) was formed inside a melamine sponge (MS) framework. After reduction with hydrazine at 60 &deg, C, the electrical conductive nitrogen-enriched rGOA-MS composite material with a specific density of 20.1 mg/cm3 was used to fabricate an electrode, which proved to be a promising electrocatalyst for the oxygen reduction reaction. The rGOA-MS composite material was characterized by elemental analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. It was found that nitrogen in the material is presented by different types with the maximum concentration of pyrrole-like nitrogen. By using Raman scattering it was established that the rGOA component of the material is graphene-like carbon with an average size of the sp2-domains of 5.7 nm. This explains a quite high conductivity of the composite obtained.

This work is devoted to the study of sanitary and hygienic monitoring of fishery water use objects in Murmansk region. The paper presents assessment of the ecological and sanitary conditions of fishery reservoirs in the Arctic region of the Kola and Tuloma rivers for the period 2016-2018 based on the use of microbiological, hydrochemical and parasitological indicators, as well as the integral index of surface water pollution. Hydrochemical studies consisted of determining the biochemical oxygen consumption, the mass content of NH4+, NO2-, NO3-, iron, and dissolved O2. The assessment of the river waters sanitary state was carried out by means of microbiological and parasitological methods. The microbiological parameters were used to determine the number of common and thermotolerant coliform bacteria, coliphages, and the presence of intestinal infections pathogens. The water of rivers does not meet the hygienic standards in terms of hydrochemical indicators in seventeen percent and in terms of microbiological indicators in five percent of cases. According to parasitological indicators, hygienic standards meet the requirements. In five points of water sampling, the water of the Tuloma and Kola rivers was evaluated as pure according to the integral hydrochemical index value and belongs to the second category of quality. In general, the high-water quality of Murmansk region rivers was noted. In conclusion, it should be emphasized that systematic monitoring of water supply sources is necessary to obtain an idea of the indicators’ variability and to assess the rivers pollution degree.

Monitoring studies of the quality of food products of plant and animal origin, including vegetable oils, some confectionery products and dietary supplements were carried out in the Murmansk region as a part of the implementing the federal project “Public Health Promotion” of the National Project “Demography”. Within the framework of monitoring studies, data allowing to evaluate the quality of food products in circulation on the territory of the Murmansk region were obtained, the share of products, up to 12% of the volume of the studied range not meeting the established requirements in safety quality indicators is revealed. The highest percentage of food products that do not conform to the technical regulation requirements is defined in the category of animal products and made up 7.8% of the total amount the of studied samples, the second place (2.5%) is given to the products of plant origin, other products – 1.8% complete the list. Toxic elements, pesticides, antibiotics, preservatives, mycotoxins, nitrates, dry low-fat milk residue, genetically modified enzymes (microbial transglutaminase) and sanitary-indicative microorganisms were determined among the safety indicators. Products of animal origin like eggs, milk, yogurt, kefir, sour cream, cake cheese, cheeses, condensed milk, butter, bockwurst sausages, sausages, were not safe for the consumer as a result of violating the production technology, including storage conditions failure, the use of low-quality raw material, or product falsification. The assessment of apples, cucumber, tomato, sunflower and olive oil, cookies and dietary supplements samples showed unsatisfactory results in the residual content of pesticides, nitrates, toxic elements, antibiotics and peroxide.

Current–voltage characteristics of few-layer graphene structures produced by electrochemical exfoliation of graphite in an electrolyte solution were measured. It was shown that few-layer graphene structures possess an electronic conductivity, which is indicative of the small degree of surface functionalization of the structures. The resistance of films formed by these structures grows with increasing relative humidity of the medium because of the shielding of fl akes of the few-layer graphene structures by a film of water.

An effect of highly oriented carbon nanowalls modification on oxygen reduction reaction was studied by means of a rotating disk electrode. Namely nanowalls were modified with oxygencontaining functional groups. Moreover, an adsorption of borneol (a surfactant with twodimensional structure) was considered. Two distinct waves are observed on voltammograms in aerated alkaline solutions that points out to the two-step process of oxygen reduction with the formation of H2O2 as intermediate. Both types of surface modification were found to affect substantially the absolute currents of the waves as well as their ratio. This effect was assumed to be caused by the topology peculiarities of carbon nanowalls that determine the electrochemical heterogeneity of the electrode surface. For initial nanowalls, the process of two-step reduction takes place on the edges of nanowalls. A parallel channel of oxygen reduction with the formation of water is assumed to be realized on the defects of basal planes at high overvoltage. In the case of noncovalent modification, borneol is adsorbed mainly on basal planes of nanowalls and blocks substantially parallel reduction channel. After covalent modification, oxygen reduction proceeds mainly through a two-step channel as a result of the increase in the number of oxygen-containing functional groups (the centers of two-step reduction) on the edges of nanowalls.

The aim of this work is to compare the electrochemical behavior of ferricenium and cobalticenium cations and supramolecular complexes formed by these cations and ferrocene with a cavitand – cucurbit[7]uril on glassy carbon and mercury electrodes. On the Hg electrode the adsorption properties of these supramolecular complexes were also studied. The substantial differences in the processes of heterogeneous electron transfer for these systems are explained by the principally different adsorption behavior of supramolecular complexes of these metallocene derivatives on GC and Hg. It was found that the mechanism of reactions of these supramolecular complexes on the Hg electrode is determined by the conditions of formation of their adlayers in the potential region preceding the beginning of electrochemical processes. For complexes formed by ferricenium cation and cobaltocene with cucurbit[7]uril we have determined the more precise values for the constants of complex formation as compared to the literature data (7 × 109 M−1and 1 × 108 M−1, respectively).

The effect of plasma electrochemical activation of boron-doped diamond compact electrodes on the oxygen electroreduction reaction kinetics is studied. The conducting compact electrodes are prepared via graphite-to-diamond conversion in C–B growth system at high pressure and high temperature. The diamond compact electrode surface was modified in Na2SO4 aqueous solution by exposition to cathodic–anodic electrolytic plasma produced by the application of voltage pulses with amplitude up to 300 V. The cathodic–anodic plasma alone proved to produce but negligible catalytic effect with respect to the oxygen reduction reaction. However, on the cathodic reduction of thus treated electrode, it acquired significant electrocatalytical activity manifested itself in the predominant O2-to-H2O reduction by a four-electron pathway. At the same time, the cathodic treatment of the plasma-modified electrodes has no real impact on the rate constant of electron transfer in the “fast” [Ru(NH3)6]2+/3+ and [Fe(CN)6]4–/3– redox systems. The observed electrocatalytical effect with respect to the oxygen reduction reaction is assumed to be caused by the quinone groups formation at the boron-doped diamond electrode surface under the combined action of cathodic–anodic plasma and cathodic polarization, these groups being active centers for the four-electron oxygen reduction.

For pristine (P-CNWs) and functionalized (F-CNWs) carbon nanowalls (CNWs), the effect of physical adsorption of certain compounds with the skeletal structure of bicyclic molecules (camphor, borneol) and also of macrocyclic compounds (Na + complexes of cryptand 222 (cryptate) and cucurbit [7]uryl) on the kinetic parameters of redox reactions ([Ru(NH 3 ) 6 ] 2 +/3 + , [Fe(CN) 6 ] 3 −/4 − and Fe 2 +/3 + ) has been studied systematically for the first time by the methods of cyclic voltammetry. It is shown, that the adsorption of these compounds on F-CNWs does not change the rate constants k 0 of [Ru(NH 3 ) 6 ] 2 +/3 + and [Fe(CN) 6 ] 3 −/4 − redox reactions, whereas their adsorption on P-CNWs leads to a decrease in k 0 by the factor 2.5–10. For the Fe 2 +/3 + reaction at the presence of organic compounds under study, the effect of inhibition is observed for P-CNWs and for F-CNWs, though to the lesser extent. The diametrically opposite effects of the adsorption of camphor and borneol on the kinetics of this reaction are observed with the transition from the pristine to functionalized electrode surface. It is shown, that the adsorption of two-dimensional condensed layers of camphor and borneol on the atomically smooth mercury surface, induces a decrease in k 0 for [Ru(NH 3 ) 6 ] 2 +/3 + reaction, substantially more pronounced, as compared to P-CNWs (by the factor of 25 and 40, respectively). This difference can be explained by the peculiarities of the topology of carbon nanowalls which determines the preferential occurrence of the redox reactions on the edges of basal planes where the formation of condensed layers by the skeletal and macrocyclic molecules seems to be complicated.

The time effects observed on mechanically renewed electrodes of eutectic-type Ag–Bi alloys in NaF solutions in the potential range of ideal polarizability are studied by traditional electrochemical methods: cyclic voltammetry and electrochemical impedance spectroscopy. The observed effects are shown to be a result of surface segregation of Bi atoms (enrichment of the metal surface layer by these atoms) realized at a rate very high as compared with usual solid-state processes. The analysis of these data carried out in the framework of phenomenological models made it possible the assumption that the mechanism of surface (not bulk) diffusion is responsible for the “anomalously” high rate of electrode surface enrichment with Bi atoms to be substantiated. The additional information on the segregation processes at the interface of Ag–Bi electrode with NaF solution acquired by the method of laser heating-induced temperature potential shift correlates with the results of electrochemical investigations.

Electron transfer rate constant decreases gradually for a Fe 2+/3+ redox system as platinum deposition covers a gold surface. This effect is assumed to be conditioned by reconstruction of double electric layer on a platinum deposit which increases reorganization energy and decreases the redox reaction rate constant.

Two types of few-layer graphene structures with different degrees of doping with nitrogen and with close surface concentrations of carbonyl groups were synthesized using the electrochemical exfoliation of graphite in the cathodic plasma mode. As for the concentrations of oxygen-containing functional groups and doping nitrogen atoms, pyridine N atoms make a dominating contribution to the electrocatalysis of oxygen reduction reaction on the synthesized structures.

Current-voltage characteristics of few-layer graphene structures (FLGS) obtained by plasma-assisted electrochemical exfoliation of graphite in Na2SO4 solution were measured. FLGS are shown to possess electronic conductivity, which indicates the predominant functionalization of the edges of graphene planes and the preservation of the structure of basal planes in obtained nanostructures as in the source graphite. The effect of humidity on the conductivity of FLGS films was studied. The resistance of films was found to increase with an increase in the relative humidity of the environment due to the shielding of FLGS flakes by a film of water. The effect of different solvents on the current-voltage characteristics of FLGS was analyzed. The conductivity of films significantly decreased in vapors of polar protic solvents, while there was a minor effect of nonpolar aprotic solvents on the conductivity of FLGS films.

Reduction of neutral binuclear tetranitrosyl iron complexes of “μ-N-C-S” structural type of [Fe2(SR)2(NO)4] composition with R being functional azaheterocyclic thiolyls has been studied by cyclic voltammetry in aprotic solvents in a wide range of potential scan rates. Redox potentials of these reactions have been determined. The consecutive transfer of two electrons was shown to be typical for all the complexes. For some complexes the products of the first electron addition are unstable, while for the others the products of reduction by both the first and the second electrons are stable. The calculations of geometric and electronic structures of monoanions, dianions and intermediates forming upon the reduction of the complexes were performed by DFT methods. Using quantum-chemical modeling, electrochemical reduction of the complexes has been studied; their energy and theoretical redox potentials have been calculated.

The changes in electrochemical and spectral characteristics of the fluorinated single-wall carbon nanotubes (F-SWCNTs) array upon electrochemical treatment were investigated. Nanotubes were characterized using cyclic voltammetry (CV), galvanostatic charge/discharge, UV–vis-NIR, Raman spectroscopy, X-ray photoemission spectroscopy (XPS), Electron Spin Resonance (ESR) spectroscopy, and scanning electron microscopy (SEM). Based on the comparative analysis of the obtained data the effect of the electrochemical treatment on the defectiveness and functionalization degree of the SWCNTs was revealed. It was shown that the addition of one oxygen-containing group was accompanied by the removal of approximately two fluorine atoms. At the same time, the defluorination leads to the partial healing of the defects formed on the nanotubes walls in the course of fluorination. The results obtained in this work in combination with our previous data on the electrochemical defluorination of the F-SWCNTs demonstrate the efficiency of the electrochemical approach for the controlled nanotube functionalization.

One-step synthesis of the nanocomposite of few-layer graphene structures with cobalt oxides was realized using the method of electrochemical exfoliation of graphite. The exfoliation process was carried out in alternating anodic-cathodic plasma mode in 1 M Na2SO4 + 0.01 M CoSO4 solution. Obtained nanocomposite was characterized by scanning and transmission electron microscopy, X-ray photoelectron and Raman spectroscopy. Besides, a catalytic activity of the nanocomposite of few-layer graphene structures with cobalt oxides towards the oxygen reduction reaction was assessed, and a considerable decrease in the oxygen reduction overpotential and an electron transfer number of ca. 3.6 were demonstrated. The observed effect was found to be caused by 40 wt% of cobalt (II) and (III) oxides in the nanocomposite.

The original and modified vertically oriented carbon nanowalls (CNWs) were applied onto conducting substrates by the plasma-chemical method. Their electrochemical behavior was studied by the methods of cyclic voltammetry and impedance measurements. The modified and original electrodes were characterized by using the methods of scanning and transmitting electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The nanowalls were modified with the functional groups (FG) via the electrolysis of aqueous solutions at the anodic potentials. Their adsorption properties were studied in the solutions of organic surfactants with the skeleton structure. It is shown that, in the first case, the number of oxygen-containing FG on the CNW surface significantly increases and, in both cases, the electrode capacitance considerably increases (by 30–50 and 3–5 times, respectively). A correlation between the rate constants k 0 of [Ru(NH3)6]2+/3+, [Fe(CN)6]4–/3–, and Fe2+/3+ redox reactions and a degree of nanowall surface functionalization is revealed. The values of k 0 were estimated in the automatic mode using a specially developed program by comparing the potential differences between the peaks of cyclic voltammograms ΔE, which were measured in a wide range of potential scan rate v, and the calculated ΔE (k 0, v) dependences, which were obtained by solving the corresponding diffusion equations. It is shown that the functionalization of CNWs leads to a substantial (by ~103 times) increase in k 0 for the Fe2+/3+ redox system and has almost no effect on the electron transfer in the [Fe(CN)6]3–/4– and [Ru(NH3)6]2+/3+ systems.

The evolution of electrochemical characteristics of a gold electrode upon the deposition of one and more atomic silver layers was studied by means of cyclic voltammetry and the method of potential temperature jump induced by the laser irradiation. Characteristics of the electric double layer on Ag monolayer are determined to be close to those of a massive silver electrode. Meanwhile, the electron-transfer parameters for the model redox system Fe(CN)63−/4− correspond to a gold electrode. The silver beyond the first atomic layer in multilayer deposits was shown to transform into Ag hexacyanoferrate (II) due to the spontaneous chemical reaction with K3Fe(CN)6 from the solution. For the Fe(CN)63−/4− redox system, the difference between oxidation and reduction peak potentials on a cyclic voltammogram increases with the growth of the silver layers number. This effect results from the corresponding increase in the ohmic resistance of the silver hexacyanoferrate (II) film and is not attributed to the changes in the electron-transfer kinetics. Keywords: Electron transfer, Heterogeneous rate constant, Silver deposits, Gold, Hexacyanoferrate (III)/(II)

The effects of electrochemical oxidation and surfactant adsorption on behavior of vertically oriented carbon-nanowall (CNW)-based electrodes are studied. Electrochemical oxidation is carried out by the electrode polarization in aqueous solutions at high anodic potentials corresponding to water electrolysis, whereas the modification of surface by surfactants is accomplished by the adsorption of molecules characterized by the cage-like structure. Using the methods of cyclic voltammetry and impedancemetry, it is shown that a substantial increase in the capacitance of CNW-based electrodes is observed in both cases (30-50-fold and 3-5-fold, respectively). The as-grown and modified electrodes are characterized by scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. A substantial increase in a number of oxygen-containing functional groups is observed on the CNW surface after the electrode polarization at high anodic potentials. The kinetics of redox reactions on the CNW film surface is studied by comparing the behavior of systems [Ru(NH3)6](2+/3+), [Fe(CN)6](4-/3-), Fe(2+/3+), and VO3(-)/VO(2+). It is demonstrated that oxidation of nanowalls makes the electron transfer in the redox reaction VO3(-)/VO(2+) and the redox system Fe(2+/3+) considerably easier due to coordination of discharging ions of these systems with the functional groups; however, no such effect is observed for the redox-systems [Fe(CN)6](3-/4-) and [Ru(NH3)6](2+/3+).

Electrochemical oxidation and subsequent electrochemical reduction of single walled carbon nanotubes was carried out by cyclic voltammetry. Using methods of Raman and absorption spectra it was revealed that oxidation of SWCNT electrodes leads to significant disruption of electronic structure of nanotubes; the structure can be substantially restored in the course of subsequent cathodic polarization. The quantitative relationship between the concentration of various oxygen-containing functional groups present on the pristine surface, electrochemically oxidized and subsequently reduced single walled carbon nanotubes was demonstrated with the use of XPS. It was shown that upon application of anodic potentials, functionalization of metallic SWCNTs proceeds deeper than in the case of semiconductor ones. The correlation between the degree of functionalization of SWCNT electrodes and kinetic parameters of electron transfer were studied using redox couples: [Ru(NH3)6]2+/3+, [Fe(CN)6]4−/3−, and Fe2+/3+. The essential growth of the electron transfer rate constant observed for couple Fe+2/+3 was suggested to results from the coordination of iron ion to oxygen from functional groups, formed at water electrolysis. It was demonstrated that the maximum rate constant for the system is reached at the medium functionalization degree.

The rare Mo=Mo double-bonded dimeric alkoxide complex [Mo2Cl4(OCH3)4(CH3OH)2] (1) was prepared by the simple methanolysis reaction of [MoCl4(CH3CN)2]. It was shown that the dissolution of 1 in thf results in the formation of the [Mo2O2Cl4(OCH3)2(thf)2] (2) and [Mo2Cl4(OCH3)4(thf)2] (3) dimers. A novel tetranuclear 10e molybdenum cluster [Mo4Cl4O2(OCH3)6(CH3OH)4] (4) was synthesized by the spontaneous disproportionation of 1 in methanol. An alternative pathway to 4 based on the redox reaction of Mo3+ and Mo5+ compounds {in the form of [MoCl3(thf)3] and [Mo2Cl4(OCH3)6] (5), respectively} was proposed and realized. The redox behavior of 4 was investigated by means of cyclic voltammetry. It was demonstrated that 4 may undergo a reversible two-electron reduction process, which implies the retention of the {Mo4} core, whereas the oxidation is irreversible, proceeding apparently with the destruction of the tetranuclear cluster core.

The new tetranitrosyl binuclear iron complex [Fe 2 (SС 5 H 5 O) 2 (NO) 4 ] ( I ) has been synthesized by the reaction of aqueous solutions of anionic salts [Fе(S 2 O 3 ) 2 (NO) 2 ] 3 − and [SС 5 H 5 O] − . The latter one has been obtained by the reduction of methyl furfuryl disulfide by hydrazine hydrate in ethanol at T = 25 °C. The molecular and crystalline structure of I has been determined by X-ray method. The complex has binuclear structure of “μ-S” type with the distance between the iron atoms ∼2.70 A. In the crystalline structure shortened intermolecular contacts of the nitrosyl groups of the adjacent molecules are observed. The maximum amount of NO generated by I in 1% aqueous solution of dimethylsulfoxide (DMSO) is ∼5 nM, and it reduces to zero in 8 min after decomposition starts in anaerobic conditions at Т = 25 °С, pH 6.5. As follows from the method of natural bond orbital analysis (NBO analysis), complex I has rather strong Fe NO bond, as compared to other NO donors. Using CVA method, the values of reduction potentials for I in an aprotic solvent have been determined, and the scheme for its reduction has been suggested.

The quantum chemical study of the redox potentials of ten iron nitrosyl complexes with functional bridging μ-SCN-type ligands was performed by the DFT method combined with the polarizable continuum model (PCM) in order to clarify the influence of the ligand on the redox properties of the complex. The geometry optimization in terms of the PCM approach gave redox potentials, which are in the best agreement with the experimental values. The redox potential depends on the nature of the heteroatom in the five-membered azole ring, the number of N atoms in the ring, and the presence of the fused benzene ring in the aromatic system of the ligand.

The mechanism of oxidation of phenazine-di-N-oxide in the presence of cyclohexanol was studied by cyclic voltammetry on glassy carbon (GC) and single-walled carbon nanotube (SWCNT) electrodes in 0.1 M LiClO4 solutions in acetonitrile. The effect of cyclohexanol on the shape of the cyclic voltammograms of phenazine-di-N-oxide and the intensity of the ESR signal of its radical cation was investigated. It was shown by ESR that the products of the one-electron oxidation and reduction of phenazine-di-N-oxide were radical cations and anions. The catalytic currents were recorded during the oxidation of phenazine-di-N-oxide on the SWCNT and GC electrodes in the presence of cyclohexanol. The results were explained in terms of the E1C1E2C2 mechanism of the two-stage electrode process characterized by the catalytic current recorded at the second electrode stage. The overall two-electron catalytic oxidation of cyclohexanol in the complex with the phenazine-di-N-oxide radical cation was assumed to occur. It was shown that SWCNT electrodes can be used in the electrocatalytic oxidation of organic compounds in the presence of the electrochemically generated phenazine-di-N-oxide radical cation.

Reduction of neutral binuclear nitrosyl iron complexes of “μ-S” structural type [Fe2(SR)2(NO)4] with R = 3-nitro-phenol-2-yl, 4-nitro-phenol-2-yl, 5-nitropyridine-2-yl and pyridine-2-yl in aprotic solution has been studied by a cyclic voltammetry (CVA) method at a wide range of potential scan rates. A complex with R = 3-nitro-phenol-2-yl was synthesized for the first time; therefore it was studied by X-ray and Mossbauer spectroscopy. The parameters of the Mossbauer spectrum are: isomer shift δFe = 0.115(1) mm s−1, quadrupole splitting ΔEQ = 1.171(1) mm s−1, and line width = 0.241(1) mm s−1 at 85 K. From the current–voltage curve, the transfer of the first electron was found to be reversible, and the redox-potentials of these reactions were determined. The further reduction of the complexes was determined to be irreversible because the product of the second electron addition is instable and decomposes partially during the potential scan. Calculations of geometric and electronic structures of monoanions and dianions of the complexes under study and their theoretical redox-potentials were performed by DFT methods. Introduction of the electron-acceptor NO2 group into the phenyl and pyridine rings of sulfur-containing ligands of the nitrosyl iron complexes was found to affect the geometry of the anions and the distribution of the additional negative charge, as well as to increase the redox-potential and to facilitate reduction of these complexes.