Showing papers on "Cyclic voltammetry published in 1971"

Spectral and electrochemical studies of the copper(ii) complexes of two macrocyclic ligands

Abstract: Copper(II) complexes of the types Cu(CR)(ClO4)2-.H2O, [Cu(CR)X](ClO4).nH2O (where X = Cl, Br, I and n = 1; X = NCS, n = 0), [Cu(CRH)](ClO4)2.H2O and [Cu(CRH)X](ClO4) (where X = Cl, Br, I) have been prepared. The ligands CR and CRH are the related four nitrogen-donor macrocycles 2,12-dimethyl-3,7,11,17-tetraazabicyclo [11.3.1]heptadeca-1(17), 2, 11, 13, 15-pentaene and meso-2, 12-dimethyl-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17), 13,15-triene, respectively. All the compounds have the normal magnetic moments expected for Cu(II) complexes with S = ½. Conductance studies in methanol show that the halo-perchlorate complexes are formally five coordinate. The probable structures of the complexes in both the solid and solution are discussed in terms of their visible, infrared and e.s.r. spectra, as well as on the basis of data obtained from conventional polarography and cyclic voltammetry.

Electrochemical Properties of Model Compounds of Nicotinamide-adenine-dinucleotide in Aqueous Solution

Abstract: The reduction behavior of N1-methyl nicotinamide iodide has been studied by drop-time controlled polarography In highly acidic media (below pH 3) two pH dependent waves were observed (I and I′) the latter having an abnormally high limiting current In the pH range of 3–10, two waves were observed (II and III), the former being pH-independent whereas the E 1/2 of the latter shifted — 60 mV per pH unit Evidence is presented for a chemical association step, possibly a dimerization occurring between reduction steps II and III Reoxidation of the reduction product of wave II was obtained at 740 mV above the potential of the wave II by cyclic voltammetry on stationary vitreous carbon electrodes This reoxidation peak is also pH independent

Electrochemical Behavior of Substituted Oxadiazoles

Abstract: An electrode reduction mechanism is reported for two aromatic‐2,5‐substituted oxadiazoles in DMF solvent as part of a continuing study of the electrochemistry of five‐membered nitrogen oxygen heterocyclics. Polarography, cyclic voltammetry, chronoamperometry, and uv spectroscopy were techniques employed in the study. The effects of a proton donor on the stability of reduction intermediates is discussed.

Organic Oxidation-Reduction Systems as Electrochemical Indicators for Monitoring in Organs in Vivo

Abstract: Electrochemical oxidation of cysteine, reduced glutathione and ascorbic acid at a platinum electrode was studied in phosphate buffer solution at pH 7.2 using cyclic voltammetry. This method makes it possible to obtain reproducible oxidation waves of these substances dissolved in blood serum. Cyclic voltammetry was also used for monitoring of cysteine and ascorbic acid in the kidney in vivo after intravenous injection of these substances. In this way cysteine or ascorbic acid function as electrochemical indicators, for example, for assessment of blood supply to the kidney.

Electrochemical Properties of Model Compounds of Nucleic Heterocycles in Aqueous Solutions

Abstract: Taking into account the biological significance of electron-exchange properties of nucleic heterocycles, we have studied the electrochemical reduction of their simplest model compound ie the pyrimidine, using drop-time controlled polarography and cyclic voltammetry on mercury drop and stationary vitreous carbon electrode The characteristics of the different reduction waves have been studied with respect to the different experimental parameters: pH, nature and concentration of buffer solutions, pyrimidine concentration, mercury flow and mechanically controlled drop-time, temperature, nature of the electrode, etc The analysis of the experimental data is discussed in terms of energetical significance of the phenomena observed Evidence is given of a chemical association step, possibly a dimerization, occuring between the two reduction steps in acid media

Electrochemical Studies of Flavins and of Metal-Flavin Interaction in Aprotic Solvents

Abstract: The nonaqueous electrochemistry of riboflavin, 3-methyllurniflavin, and phenazine has been studied at a platinum electrode in DMSO, DMF, and CH3CN. Cyclic voltammetry, chronopotentiometry, and controlled potential electrolysis have been used to determine the stoichiometry, thermodynamics, and kinetics of the electron transfer processes. The results indicate that the three model compounds are reduced in neutral solutions by two one-electron steps with a stable anion radical produced by the first of these. Under acidic conditions the model compounds are reduced by a single two-electron process. Reduction mechanisms are proposed which are consistent with the electrochemical data and products. The interactions of the radical anion species with Fe2+, Ni2+, Y3+, La3+, Th4+, Ca2+, and Na+ ions have been investigated and the relative stabilities of the resulting complexes have been evaluated. Disproportionation of the radical anion appears to be promoted by the higher valent metal ions. The electrochemical data provide a basis for proposing an electron transfer mechanism for metallo flavoenzymes.

Identification of Gold Islands on Copper‐Plated Wire Surfaces by Cyclic Voltammetry

Abstract: Periodic potentiostatic current‐potential curves have been used to demonstrate the existence of gold islands on a copper substrate. The samples of smooth and rough copper substrates were prepared in a continuous wire plating system with an average thickness of the gold deposit of from 0 to 1400A. Time‐dependent changes in the potentiostatic curves were qualitatively explained in terms of the respective electrode reactions.

Electrochemical Investigation of Kinetic and Allied Aspects of Biological Redox Reactions

Abstract: The relations are summarized between potential, current and derived data, as obtained by polarographically derived technics, and (a) reversibility of electron-transfer processes and the various factors producing irreversibility in such processes, and (b) the study of homogeneous solution kinetics, the kinetics of reactions occurring near the electrode whose equilibria are perturbed by electrolytic processes, and heterogeneous electron-transfer kinetics.

Cyclic Voltammetry of Electrodeposition and Reduction of Manganese Dioxide

Abstract: 酸性溶液中における二酸化マンガンの電解析出および還元反応をサイクリックボルタメソトリーにより検討を行ない,主に還元反応について考察した。えられた結果を要約すると次のとおりである。(1)二酸化マンガンの析出電位は,pHが高くなると卑になるが,酸素発生電位は逆に貴になる。(2)還元反応の分極曲線はpHにより異なった傾向を示す。pH1。2以下では,二酸化マンガンの溶解につづいて低次の酸化物の溶解に対応したピークがあらわれる。(3)pH2以上になると,二酸化・マンガンから低次の酸化物への還元反応および低次の酸化物の溶解に対応したピークがみられ,二酸化マンガンの還元反応は低次の酸化物を経由する反応と考えた。

Polarographic studies of nickel‐DL‐tryptophan solutions

Abstract: The polarography of Nickel (II) in the presence of DL-tryptophan has been studied in KNO3 supporting electrolyte. Nickel yields two irreversible steps which are due to the formation of two varieties of complex in sluggish equilibrium with each other. The reduction is an irreversible, kinetically controlled process as evidenced from cyclic voltammetry and i–t curves. Rate constants of the processes are evaluated. The effect of temperature is described.