Irreversible One-electron Waves Research Articles

Synthesis, characterization, and crystal structure of cobalt(II) complex with 2-oximino-3-thiosemicarbazone-2,3-butanedione

The reaction of cobalt(II) chloride with the tridentate ligand 2-oximino-3-thiosemicarbazone-2,3-butanedione [Hotsb (1)] leads to the formation of the novel six-coordinated complex [Co(otsb)2]·2H2O (2). This complex has been synthesized and characterized by X-ray crystallography, spectroscopic and cyclic voltammetric measurements. The ligand Hotsb (1) obtained by the condensation of 2,3-butanedione monoxime and thiosemicarbazide is used for the preparation of complex 2. The Hotsb (1) crystallizes into a monoclinic lattice with space group P21/c. The crystal structure of 2 shows a distorted mer-octahedral geometry in which the ligands are coordinated as uninegatively charged tridentate chelating agents via the hydrazine nitrogen atoms, the azomethine nitrogen atoms, and the thiolate sulfur atoms. The cyclic voltammogram of 2 undergoes two irreversible one-electron waves corresponding to CoII/CoIII and CoII/CoI processes.

Synthesis of new oxamide-based ligand and its coordination behavior towards copper(II) ion: Spectral and electrochemical studies

A new ligand N, N′-bis{3-(2-formyl-4-methyl-phenol)-6-iminopropyl}oxamide ( L) and its mono- and binuclear copper(II) complexes have been synthesized and characterized. The ligand shows absorption maxima at 249 and 360 with a weak transition at 455 nm. The ligand was found to be fluorescent and shows an emission maximum at 516 nm on excitation at 360 nm. The electronic spectra of the mono- and binuclear Cu(II) complexes exhibited a d–d transition in the region 520–560 nm characteristic of square planar geometry around Cu(II) ion. The ESR spectrum of the mononuclear complex showed four lines with nuclear hyperfine splitting. The binuclear complex showed a broad ESR spectrum with g = 2.10 due to antiferromagnetic interaction between the two Cu(II) ions. The room-temperature magnetic moment values ( μ eff) for the mono- and binuclear Cu(II) complexes are found to be 1.70 μ B and 1.45 μ B, respectively. The electrochemical studies of the mononuclear Cu(II) complex showed a single irreversible one-electron wave at −0.70 V ( E pc) and the binuclear Cu(II) complex showed two irreversible one-electron reduction waves at −0.75 V ( E pc 1 ) and −1.27 V ( E pc 2 ) in the cathodic region.

Synthesis, structural characterization of nickel(II) hexaazamacrotetracyclic complexes with azido, isocyanato and nitrito ligands

The reaction of [Ni(L)](ClO 4) 2·2H 2O (L=1,3,10,12,16,19-hexaazatetracyclo[17,3,1,1 12.16,0 4.9]tetracosane) with NaN 3, NaNCO and KNO 2 yields mononuclear nickel(II) complexes, [Ni(L)(N 3) 2]·2H 2O (1), [Ni(L)(NCO) 2]·2H 2O (2) and [Ni(L)(ONO) 2]·2H 2O (3). These complexes have been characterized by X-ray crystallography, electronic absorption and cyclic voltammetry. The crystal structures of the complexes show that all structures are centrosymmetric and the nickel centre has an axially elongated octahedral geometry with four nitrogen atoms of the macrocycle and two coordinated axial ligands. Electronic spectra of the complexes also exhibit a high-spin octahedral environment. Cyclic voltammetry of the complexes undergoes a irreversible one-electron wave corresponding to Ni(II)/Ni(I) processes. The electronic spectra and electrochemical behaviors of the complexes are significantly affected by the nature of the azido, isocyanato and nitrito ligands.

Voltammetric studies of the electrochemical behaviour of salicylidene-2-aminopyridine at a hanging-mercury-drop-electrode

Electrochemical behaviour of salicylidene-2-aminopyridine has been investigated in 0.1 M tetraethylammonium perchlorate–dimethylformamide solutions by cyclic voltammetric and convolution potential sweep voltammetric methods. It was found that the depolarizer exhibits two well-defined diffusion-controlled irreversible one-electron waves. The cyclic voltammetric characteristics and the convolution, deconvolution, and logarithmic convolution analyses reveal that salicylidene-2-aminopyridine in such conditions follows a set of two one-electron transfer reactions each followed by an irreversible chemical reaction. The values of the first-order rate constant of the irreversible chemical reaction and E1/2 were computed.

Electroreduction of phenol red, chlorophenol red and bromophenol red in buffer solutions at DME

The polarographic reduction of phenol red, chlorophenol red and bromophenol red has been investigated in buffered aqueous solutions and alcohol-water water mixtures over a widepH range (2–12). The results show that the three depolarizers are reduced through two irreversible one-electron waves of equal heights at allpH values. The two waves represent the reduction of the triphenylmethane carbon centre. The nature of the waves and the kinetics of the electrode reaction are discussed.

Electrochemical Oxidation of Derivatives of Dibenzodiazepin. Dibenzothiazepin and Dibenzoxazepin

Abstract Clozapin exhibits two anodic waves at ≥ 1 M H2SO4, but at lower acidities only the first two-electron wave remains. Cyclic voltammetry shows an ECE mechanism. Reversibility decreases at ≥ 10−4 M concentrations, due to formation of an adsorptiob film. In nonaqueous solvents two irreversible one-electron waves appear. Clothiapin and loxapin are more difficultly oxidized and can be measured in the presence of clozapin.

Electrochemical reduction of 1, 4-dihydropyridine-3, 5-dicarboxylic acid derivatives in an aprotic medium

The polarographic reduction of 1, 4-dihydropyridine-3, 5-dicarboxylic acid derivatives in dimethylformamide was studied. It is shown that the first diffusion waves of these compounds are irreversible one-electron waves and correspond to electrical reduction of the C=C bond of the conjugated system of the 1, 4-dihydropyridine ring to give a tetrahydro derivative. In the case of pyridine-3, 5-dicarboxylic acid esters partial dimerization of the resulting freeradical products occurs along with electron transfer. It is shown that the introduction of alkoxycarbonyl substituents in 2, 6-methyl and 3, 5-methoxycarbonyl groups and in the 4 position and of a carboxyl group in the 4 position facilitates the electrical reduction of the 1, 4-dihydropyridine ring. The introduction of a methyl group in the 4 position hinders reduction of the ring.