Modelling reversible cyclic voltammetry at the one-dimensional junction established by three phases: an organic liquid containing a neutral electroactive solute,an aqueous electrolyte solution,and an electronic conductor

Scholz et al. (Electrochem. Commun. 2 (2000) 112) recently performed cyclic voltammetry on droplets of a solution of decamethylferrocene (dmfc) in nitrobenzene (nb) lying between graphite and an aqueous solution of potassium chloride. Those authors hypothesized that the reaction dmfc(nb)+Cl⁻(aq)→dmfc⁺(nb)+Cl⁻(nb)+e⁻ took place at the hoop where the three phases meet. We have modelled this hypothesis on the basis that the cyclovoltammetric current is controlled by Nernst’s law and by the cylindrical diffusion of dmfc to, and of dmfc⁺Cl⁻ from, the three-phase junction. Model and experiment do not match.     

Ion insertion into ionic liquid supported toluene generated by electrochemical redox reaction

Ion transfer across the toluene|water, toluene–ionic liquid mixture|water and ionic liquid|water boundary generated by electrochemical redox reaction of tert-butylferrocene (tBuFc) was studied with the glassy carbon (GC) electrode partially covered by the organic liquid deposit and immersed in the aqueous electrolyte solution. The electrooxidation of the redox probe in toluene deposit is followed by ejection of newly formed cation into the aqueous solution. The same reaction in the toluene–ionic liquid deposit promotes anion insertion. This pathway is also found at the electrode modified with ionic liquid.     

Experimental Evidence for a Calix[4]arene-Proton Complex

Summary. From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium H⁺(aq) + 1 ·Na⁺(nb) ⇆ 1 ·H⁺(nb) + Na⁺(aq) taking place in the two-phase water-nitrobenzene system (1 = p-tert-butylcalix[4]arene-tetrakis(N, N-diethylacetamide); aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K _ex(H⁺, 1 ·Na⁺) = −1.4 ± 0.1. Further, the stability constant of the p-tert-butylcalix[4]arene-tetrakis(N,N-diethylacetamide)-H⁺ complex in water saturated nitrobenzene was calculated for a temperature of 25°C as log β_nb(1 · H⁺) = 8.1 ± 0.1.     

Distribution of three ions in the thin film experiment

In the theoretical model it is assumed that a graphite disk electrode is covered by a thin film of the solution of decamethylferrocene and some supporting electrolyte in nitrobenzene and immersed in an aqueous solution of the same electrolyte. Oxidation of decamethylferrocene is accompanied by the transfer of anions of the electrolyte from water into nitrobenzene. The flux of decamethylferrocenium cations at the electrode surface and the flux of anions at the liquid/liquid interface are separated by the thickness of the film, but the electroneutrality is ensured by the migration of ionic species through the film. Theoretical concentration profiles of ionic species in the film are reported for cyclic voltammetry.     

Analytical applications of electrode sensitive to labetalol in pharmaceuticals

The analytical properties of an ion-selective electrode sensitive to labetalol with a liquid membrane, based on ion-pair complexes with sodium tetraphenylborate (TPB-Na⁺) are described. The studied electrode can be used for the determination of labetalol hydrochloride as a protonated form of labetalol in pharmaceuticals. The calibration curve, e.g. EMF=f(pC _LabHCl ) is linear in the range from 10⁻⁵ to 10⁻² mol L⁻¹ with a correlation coefficient of 0.9992 and slope of 61.13 mV/decade, which is close to the Nernstian slope. The detection limit of the examined electrode is 7.20×10⁻⁶ mol L⁻¹. The influence of pH of the tested solutions on the formulation of the electrode is not as considerable since the electrode works correctly in the pH range 3.0–8.0. The main attributes of the developed electrode are: stability, good reproducibility of EMF and short response time, close to 30 seconds depending on labetalol concentration in the solution. The electrode shows good selectivity for many inorganic ions. The selectivity for drug cations is weaker due to the structural similarity of the interfering cations to labetalol. The results of labetalol determination using direct potentiometry in drugs such as Pressocard (Polpharma) and Trandate (GlaxoWellcome) were compatible with the quantity of labetalol declared by the manufacturer, and with parallel UV spectrophotometric and HPLC determinations.     

An electrochemical method for determination of the standard Gibbs energy of anion transfer between water and n-octanol

The transfer of the ions Cl⁻, Br⁻, I⁻, ClO₄⁻, SCN⁻, NO₃⁻, BF₄⁻, and (C₆H₅)₄B⁻ across the water|n-octanol (W|OC) liquid interface was studied and the standard Gibbs energies of ion transfer were determined. The ion transfer was achieved by oxidation of decamethylferrocene dissolved in a droplet of n-octanol that was attached to a graphite electrode immersed in the aqueous solutions of the respective alkali salts of the anions. The electrode reaction can be described by the equation: dmfc_(OC)+X_(W)⁻⇄dmfc⁺_(OC)+X⁻_(OC)+e⁻, where X⁻ is the transferred anion. Square-wave voltammetry at this three-phase arrangement was utilised to determine the formal potential of the decamethylferrocene/decamethylferrocenium (dmfc/dmfc⁺) couple under the condition of ion transfer across the water|n-octanol interface. For calibration the standard Gibbs energies of ion transfer have been extrapolated to octanol from the series of known data for methanol, ethanol, n-propanol, and n-butanol. All these data are consistent and the experimental dependence of the formal potentials on the standard Gibbs energies is as predicted by theory. The validity of data is further supported by calculations of Gibbs energies of ion transfer using the Born theory. Until now it was not possible to perform electrochemical measurements at the water|n-octanol interface because in the conventional four-electrode cells this interface cannot be polarised. With the new method it is now for the first time possible to determine the Gibbs energies of transfer of ions across the water|n-octanol interface. These values are of very wide use for assessing the lipophilicity of compounds in chemistry, medicine, and pharmacology.     

Ti3C2Tx/MnO2正极在水系锌电池中的电化学性能

二氧化锰(MnO₂)材料具有比容量大、电极电位高、储量丰富以及价格低廉等优势,成为水系锌电池正极最受关注的一类材料,然而其仍然存在着结构稳定性差和电化学储存机理复杂的问题。因此,我们通过两步合成法制备了一种花苞状结构的MnO₂负载在Ti₃C₂T_x表面形成Ti₃C₂T_x/MnO₂复合材料,通过X射线粉末衍射(XRD)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)和高分辨透射电子显微镜(HRTEM)对复合样品的结构、成分和形貌进行表征。通过将Ti₃C₂T_x/MnO₂复合材料作为正极,与锌负极匹配组装成水系锌电池,研究了其分别在2 mol·L^-1 ZnSO₄、2 mol·L^-1 ZnSO₄+0.1 mol·L^-1 MnSO₄、30 mol·L^-1三氟甲基磺酸四乙基铵(TEAOTf)+1 mol·L^-1三氟甲烷磺酸锌(ZnOTf)和3 mol·L^-1 ZnOTf四种电解液中的电化学性能。结果表明,Ti₃C₂T_x/MnO₂在2 mol·L^-1 ZnSO₄中的比容量较高,但循环稳定性很差。将TEAOTf盐和ZnOTf盐共溶于水中,设计了一种新型的含惰性阳离子的超高浓度盐包水电解液(30 mol·L^-1 TEAOTf+1 mol·L^-1 ZnOTf),不仅提高了Ti₃C₂T_x/MnO₂材料的可逆性,而且有效抑制了电极材料在循环过程中的溶解。     

Cyclic Voltammetry of Ion Transfer for Phenylpropanolamine Hydrochloride at Water|Nitrobenzene Interface

The transfer on phenylpropanolamine ion, PPAH⁺, has been studied at the Interface between Two Immiscible Solutions (ITIES). The polarizable potential range was determined by cyclic voltammetry at the interface between an aqueous solution of lithium chloride (LiCl) and a nitrobenzene (NB) solution of electrolyte tetrabutylammonium tetraphenylborate (TBATPB). The half‐wave potential of ion transfer for phenylpropanolamine accross the water|NB interface was found 465.3 mV. The peak separation, the diffusion coefficient, and the standard ion transfer potential of PPAH⁺ were observed to be 59.1 mV, 1.7 × 10^?6 cm²/s, and 104.6 mV, respectively. The temperature of experiment was kept constantly at 25 ± 1 °C using water flow thermostate.     

New ionic liquid for inorganic cations analysis by capillary electrophoresis: 2-hydroxy- N , N , N -trimethyl-1-phenylethanaminium bis(trifluoromethylsulfonyl)imide (phenylcholine NTf2)

The potentialities of new ionic liquids (ILs) based on choline were evaluated as an electrophoretic medium in capillary electrophoresis for the analysis of alkaline and alkaline earth cations (Li⁺, K⁺, Na⁺, Cs⁺, Mg²⁺, Ba²⁺, Ca²⁺, and Sr²⁺) with indirect UV detection. Two types of capillaries were tested: an untreated fused silica and fused silica coated with a film of polyvinylalcohol. The coated capillary proved to be the best adapted for the metal ions studied. Moreover, it appeared that the nature of the ionic liquid anion influenced the baseline stability, and the bis(trifluoromethylsulfonyl) imide (NTf₂ ⁻) anion seemed to be the most efficient. These preliminary studies led us to synthesize a new ionic liquid, 2-hydroxy-N,N,N-trimethyl-1-phenylethanaminium NTf₂ (phenylcholine NTf₂). This liquid was able to act as the running electrolyte and probe, generating the background signal in indirect UV light and consequently simplifying the electrophoretic medium. Excellent baseline stability, good reproducibility, as well as good sensitivity of detection were obtained with this new ionic liquid. Thus, 510,000 plates/meter for Li⁺ with 40 mM IL were successfully obtained. The optimal concentration of IL was 20 mM with a detection limit ranging from 28 μg L⁻¹ for Li⁺ to 1,000 μg L⁻¹ for Cs⁺. This method (phenylcholine NTf₂ with polyvinylalcohol capillary) was applied to analyze different commercial source and mineral waters. Finally, the potentiality of this ionic liquid in nonaqueous capillary electrophoresis was explored. The use of phenylcholine NTf₂ with a fused silica capillary, in pure methanol medium and in the presence of acetic acid, made it possible to obtain separation selectivity different from that obtained in aqueous medium.     

Recycling of NAD+ using coimmobilized alcohol dehydrogenase andE. coli

The use of immobilized enzymes has opened the possibility of large scale utilization of NAD⁺-linked dehydrogenases, but the applications of this technique were limited by the necessity of providing the large amounts of NAD⁺ required by its stoichiometric consumption in the reaction. After immobilization of alcohol dehydrogenase and intactE. coli by glutaraldehyde in the presence of serum albumin, the respiratory chain was found to be capable of regenerating NAD⁺ from NADH. This NAD⁺ can be recycled at least 100 times, and thus the method is far more effective than any other, and, moreover, does not require NADH oxydase purification. The total NADH oxidase activity recovered was 10–30% of the initial activity. Although, NADH is unable to cross the cytoplasmic membrane, it was able to reach the active site of NADH dehydrogenase after immobilization. The best yield of NADH oxidase activity with immobilized bacteria was obtained without prior treatment of the bacteria to render them more permeable. The denaturation by heat of NADH oxidase in cells that are permeabilized was similar before and after immobilization. In contrast, the heat denaturation of soluble Β-galactosidase required either a higher temperature or a longer exposure after immobilization. The sensitivity of immobilized NADH oxidase to denaturation by methanol was decreased compared to permeabilized cells. As a result, it is clear that the system can function in the presence of methanol, which is necessary as a solvent for certain water insoluble substrates.     

Studies of Thermochemical Properties of a New Ionic Liquid Prepared by Mixing 1-Methyl- 3-Pentylimidazolium Chloride with InCl3

A new ionic liquid, PMIInCl₄, was prepared by mixing 1-methyl-3-pentylimidazolium chloride (PMIC) with InCl₃. The molar enthalpies of solution of PMIC and PMIInCl₄ in water to form solutions at various molalities were determined at 298.15 K using an isoperibol calorimeter. Using Pitzer's electrolyte solution model, the molar enthalpies of solution of PMIC and PMIInCl₄ at infinite dilution, Δ_sol H^_m, and Pitzer's ion-interaction parameters β_MX ^(0)L, β_MX ^(1)L and C_MX ^ϕL, were derived. The values of the apparent relative molar enthalpy L and relative partial molar enthalpy of the solutes (PMIC and PMIInCl₄), , were subsequently calculated. Using the values of Δ_sol H^_m of PMIC, PMIInCl₄ and InCl₃, the enthalpy change, Δ_r<H=−38.19kJ·;mol^-1, was calculated for the reaction PMIC + InCl₃ → PMIInCl₄     

Formation of negative oxidation states of platinum and gold in redox ionic liquid: Electrochemical evidence

The electrochemical reduction of noble metal electrodes in the presence of redox ionic liquid, 1-ferrocenylethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [FcEMIM][TFSI], was investigated by cyclic voltammetry. Our experiments suggest the formation of metal with negative oxidation states, in the cases of platinum and gold electrodes [M_n⁻, FcEMIM⁺]. By analogy with the previous work, the formation of these phases is concomitant with the insertion of the supporting electrolyte; which correspond in our experimental condition to the redox cation of the ionic liquid. As an exciting result, the electrochemical investigations of the reduced electrode in electrolytic solution, containing solvent and supporting electrolyte, evidence the presence of the ferrocene groups at the electrode surface. Moreover, the reduced electrode exhibits the presence of the ferrocene even after, contact with air, after ultrasound, and after physical polishing, highlighting the large stability of this organo-metallic phases formed in this media. The AFM investigations demonstrate the morphological change of the platinum surface after the reduction process. Finally, our works bring a formal electrochemical proof of the presence of the ionic liquid cation inside the electrode material after the cathodic treatment in this media.     

A Cryptate Reference Electrode for Ionic Liquids

The cryptate electrode (Ag/Ag⁺222), prepared by immersing silver wire in a solution of silver(I) salt and the cryptand 222 (4,7,13,16,21,24‐hexaoxa‐1,10‐diazabicyclo[8.8.8]hexacosane) in ionic liquids have been studied. The potential of the electrode is stabilized by the equilibrium of the Ag⁺ ion complexation by the cryptand, similarly to the potential stabilization by the ionic product of slightly soluble salts, used in aqueous electrodes of the second kind. The Ag/Ag⁺222 cryptate electrode (concentration of the cryptate was much higher than the silver(I) cation concentration, [222]>[Ag⁺]) may be used as a reference electrode in room temperature ionic liquids. The potential of the Ag/Ag⁺222 electrode is less sensitive to the presence of impurities, such as halides or water, in comparison to the Ag/Ag⁺ electrode. After anodic or cathodic polarization, the potential of the Ag/Ag⁺222 electrode comes back to the initial open circuit potential quickly. Preparation of the Ag/Ag⁺222 reference electrode is very easy: a silver wire is immersed in a solution of Ag⁺ salt and cryptand 222 (both available commercially) in the ionic liquid under study.     

Successful establishment of MEKC with electrochemiluminescence detection based on one functionalized ionic liquid

Herein, one water‐soluble functionalized ionic liquid, 1‐butyl‐3‐methylimidazolium dodecyl sulfate ([BMIm⁺][C₁₂H₂₅SO^?₄]), was designed and its superiorities either used as supporting electrolytes or as additives for successful establishment of MEKC with electrochemiluminescence (ECL) detection (MEKC‐ECL) method were investigated. Compared with the common supporting electrolytes such as phosphate solution, 1‐butyl‐3‐methylimidazolium dodecyl sulfate solution used as running buffers led to greatly enhanced ECL intensities and column efficiencies for negative targets, a little increase for neutral‐charge ones while maintained nearly unchanged for positive ones due to the electrostatic forces between the large cation BMIm⁺ and the solutes and the hydrophobic interactions resulting from the large anion C₁₂H₂₅SO^?₄. Moreover, resolution efficiency between analytes was significantly improved. As the existence of ionic liquid moiety, BMIm⁺, accelerated the electron transfer at the electrode surface, the poisoning effect of long chain C₁₂H₂₅SO^?₄ on the electrode surface was eliminated and reproducible ECL intensities with relative standard derivation of 1.02% (n=6) were obtained. The proposed novel MEKC‐ECL system was again validated by the baseline separated two similar amino acids of proline and hydroxyproline with lower detection limits of 0.5 and 0.8 μM (S/N=3), respectively.     

Effects of carbon nanofiber composites on electrode processes involving liquid|liquid ion transfer

Composite electrodes were prepared from chemical vapor deposition grown carbon nanofibers consisting predominantly of ca. 100 nm diameter fibers. A hydrophobic sol–gel matrix based on a methyl-trimethoxysilane precursor was employed and composites formed with carbon nanofiber or carbon nanofiber—carbon particle mixtures (carbon ceramic electrode). Scanning electron microscopy images and electrochemical measurements show that the composite materials exhibit high surface area with some degree of electrolyte solution penetration into the electrode. These electrodes were modified with redox probe solution in 2-nitrophenyloctylether. A second type of composite electrode was prepared by simple pasting of carbon nanofibers and the same solution (carbon paste electrode). For both types of electrodes it is shown that high surface area carbon nanofibers dominate the electrode process and enhance voltammetric currents for the transfer of anions at liquid|liquid phase boundaries presumably by extending the triple-phase boundary. Both anion insertion and cation expulsion processes were observed driven by the electro-oxidation of decamethylferrocene within the organic phase. A stronger current response is observed for the more hydrophobic anions like ClO₄⁻ or PF₆⁻ when compared to that for the more hydrophilic anions like F⁻ and SO₄²⁻. Presented at the 4th Baltic Conference on Electrochemistry, Greifswald, March 13–16, 2005     

Possible key intermediates in arsenic biochemistry: Synthesis and identification by liquid chromatography electrospray ionization mass spectrometry and high resolution mass spectrometry

Arsenic is a type 1 carcinogen and its toxicity is critically dependent on chemical speciation. However, after decades of research, the biogenesis of at least fifty naturally occurring arsenic species is still not well understood.Here, based on experimental work, it is proposed a set of pathways for the formation of multiple arsenic species that might help to clarify the present situation.These are focused on the thiol protein arsenic bond and on its interaction with reactive metabolites. In fact, arsenic bound to glutathione interacting with sulfur adenosyl methionine (SAM), MethylCB₁₂ and AdoCB₁₂, forms a number of complexes that might be key intermediates in arsenic biochemistry. These include dimethylarsino glutathione (DMAG) m/z 412 [M + H]⁺, synthesized non-enzymatically from glutathione and cacodylate. Trimethylarsonio glutathione (TMAG) m/z 426 [M]⁺ synthesized from DMA, GSH and SAM, apparently by a classical Challenger methylcarbonium attack. Tetramethyl arsonium ion m/z 135 [M]⁺ is formed in a third step, apparently by carbanion methylation. The presence of trimethylarsine oxide (TMAO) m/z 137 [M + H]⁺ is attributed to the hydrolysis of TMAG or TMA, or to carbanion methylation of dimethylarsinoyl glutathione (m/z 428 [M]⁺) formed from cacodylate and GSH. Cantoni type attacks of DMAG on SAM were unsuccessful, eventually due to competition of the trivalent S⁺ atom of SAM for the As^III atom attack. The presence of dimethylarsonio diglutathione (DMADG m/z 717 [M]⁺), is suggested to result from a GS^- attack on dimethylarsenoyl glutathione (m/z 428 [M + H]⁺). The presence of dimethylarsenoyladenosine (m/z 372 [M + H]⁺), trimethylarsenosugar adenine (m/z 370 [M]⁺), and dimethylthioarsenosugar adenine (m/z 388 [M + H]⁺), is explained by the synthesis of the pecursor dimethylarsonio-adenosine glutathione DMAAG (m/z 661 [M]⁺), a likely source of oxo-and trimethylated arsenosugars, as well as of thio-arsenosugars by the cleavage of its S-C bond. The results gathered suggest that cell vacuoles might play a major role in arsenic metabolism, and that the dominance of oxo-As sugars, in algae extracts, may be supported by a mechanism of synthesis independent of DMAAG (m/z 661).They also offer an explanation for the reason why arsenobetaine, and tetramethylarsonium are loosely bound to biotic tissues. Four arsenic species new to science, to the best of our knowledge, and a number of known arsenic compounds were synthesized in this work, identified by HPLC–ESI-MSⁿ and FTICR–ESI-MS, and suggestions regarding their mechanisms of synthesis were advanced. These results provide a framework for arsenic biochemistry which may explain the origin of a significant part of arsenic known metabolites.     

Removal of <Superscript>60</Superscript>Co<Superscript>2+</Superscript> and <Superscript>137</Superscript>Cs<Superscript>+</Superscript> ions from low radioactive solutions using <Emphasis Type="Italic">Azolla caroliniana</Emphasis> willd. water fern

This study concerns the removal of the ¹³⁷Cs⁺ and ⁶⁰Co²⁺ β+γ-radioactive ions in Azolla caroliniana Willd. water fern. The living fern and two different types of biosorbent prepared from Azolla caroliniana were tested to remove the above-mentioned radioactive ions from dilute solutions, in the absence and in the presence of the ionic competition. Effective ¹³⁷Cs⁺ and ⁶⁰Co²⁺ ions removal from low radioactive wastewaters was demonstrated. The time dependent K _d (t) values were calculated from the absorption data. These results indicate that removal process achieved equilibrium in about 120 min and that it involves two steps: rapid and slow absorption; the active process (metabolic bioaccumulation on the living fern) was responsible for above one half of the total removal process. A thin layer radiochromatography study leads to the conclusion that the biochemical components in which ¹³⁷Cs⁺ and ⁶⁰Co²⁺ place themselves are of a polysaccharide and lipoid fractions.     

Inner-sphere electron transfer in metal-cation chemistry

Bond activation of organic molecules by metal cations is usually rationalized either in terms of the chemistry of Lewis acids or via oxidative addition of metal fragments to R---X bonds, that is, R---X+M⁺→R---M⁺---X→products. In most of these mechanisms, the positive charge is assumed to be located on the metal center. Here, we propose an alternative mechanism, to which we refer as inner-sphere electron transfer (ET). Thus, provided that certain conditions are fulfilled, the insertion species R---M⁺---X may isomerize via ET to [ R⁺ MX] structures with the positive charge located mostly at the organic residue R. If R---M⁺---X and [ R⁺ MX] are not just resonance structures but distinct minima on the related potential-energy surfaces, there also exists a transition structure between the two, that is, an ET-TS. Here, the role of inner sphere ET in organometallic gas-phase reactions and the possible existence of ET-TSs are discussed for a series of examples investigated both computationally and experimentally.     

Sensitive Voltammetric Response of p‐Nitroaniline on Single‐Wall Carbon Nanotube‐Ionic Liquid Gel Modified Glassy Carbon Electrodes

An ionic liquid (i.e., 1‐butyl‐3‐methylimidazolium hexafluorophosphate, BMIMPF₆)‐single‐walled carbon nanotube (SWNT) gel modified glassy carbon electrode (BMIMPF₆‐SWNT/GCE) is fabricated. At it the voltammetric behavior and determination of p‐nitroaniline (PNA) is explored. PNA can exhibit a sensitive cathodic peak at ?0.70 V (vs. SCE) in pH 7.0 phosphate buffer solution on the electrode, resulting from the irreversible reduction of PNA. Under the optimized conditions, the peak current is linear to PNA concentration over the range of 1.0×10^?8–7.0×10^?6 M, and the detection limit is 8.0×10^?9 M. The electrode can be regenerated by successive potential scan in a blank solution for about 5 times and exhibits good reproducibility. Meanwhile, the feasibility to determine other nitroaromatic compounds (NACs) with the modified electrode is also tested. It is found that the NACs studied (i.e., p‐nitroaniline, p‐nitrophenol, o‐nitrophenol, m‐nitrophenol, p‐nitrobenzoic acid, and nitrobenzene) can all cause sensitive cathodic peaks under the conditions, but their peak potentials and peak currents are different to some extent. Their peak currents and concentrations show linear relationships in concentration ranges with about 3 orders of magnitude. The detection limits are 8.0×10^?9 M for p‐nitroaniline, 2.0×10^?9 M for p‐nitrophenol, 5.0×10^?9 M for o‐nitrophenol, 5.0×10^?9 M for m‐nitrophenol, 2.0×10^?8 M for p‐nitrobenzoic acid and 8.0×10^?9 M for nitrobenzene respectively. The BMIMPF₆‐SWNT/GCE is applied to the determination of NACs in lake water.     

Synthesis and electrochemical characterization of CoII, NiII, and CuII complexes with organic N2S2-type ligands derived from 2-thio-substituted benzaldehydes and aromatic amines

Transition metal complexes (Ni^II, Co^II, and Cu^II) with tetradentate N₂S₂-type ligands (L), which are reaction products of 2-thio-substituted benzaldehydes with aromatic amines (3-aminopyridine or 2-aminothiophenol), were synthesized for the first time. The complexes have the composition L·MX₂ or L·2MX₂ (X = Cl or ClO₄). The electrochemical behavior of the ligands and complexes was studied by cyclic voltammetry and rotating disk electrode voltammetry. Depending on the structure of the complexes, the metal atom in the latter is initially reduced in a one-or two-electron process. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2115–2124, November, 2007.