electrochemical studies of copper(II)complexes of Diamines, (Part 1).Electrochemical studies of copper(II) complexes of ethylenediamine at various pH values (original) (raw)
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The cyclic voltammetric behaviour of copper (II) tetraethylethylene systems with [ Cu(II): [teen] =1:10, 1:100 molar ratios ,1x 10-3M cu(ClO4)2.6H2O in aqueous 0.2m NaClO4 supporting electrolyte have been studied at ph 7.20, 9.10 and 10,85. The electrode process show quasi reversible one electron charge transfer preceded and folloed by chemical reaction at glassy carbon electrode( GCE). For a given [ Cu(II)]:[teen] molar ratio, Epc1 for 1:10=1:100 indicatig stability of complex species follow the same trend contrary to expectation. however, at a given metal; ligand ratio and at a given ph, Epc1 shifts anodically in the order em-tmen-teen, indicating that the ease of reduction also follows the same trend.
Zenodo (CERN European Organization for Nuclear Research), 2011
The electrochemical behaviour of [Cu(tmen)X 2 ] (where tmen = N,N,N',N'-tetramethylethylcnediamine and X = Cl or Br) has been studied in dimethylsulfoxide (DMSO) solution containing 0.1 M tctrabutylammoniumpercblorate (TBAP) as supporting electrolyte at a platinum working electrode. The dirrusion-controlled reduction of both the complexes occurred in two stages; the first one at # = 342 to 352 and second at # = 16 to 24 mV vs Ag/AgCI. The anodic to cathodic peak current ratio is greater than unity for the nrst redox couple while it is less than 1.0 for the second couple, suggesting that the elec:trogenerated cu•-complex species is weakly adsorbed in the former case while the second step involves electron transfer followed by a chemical reaction (EC mechanism). The two redox proce~se~ observed may be because of chemical equilibrium between the two complex species in DMSO medium.
Electroanalysis, 2012
Mixed ligand dinuclear copper(II) complexes of the general formula [Cu 2 (Rdtc)tpmc)](ClO 4 ) 3 with octaazamacrocyclic ligand tpmc and four different heterocyclic dithiocarbamate ligands Rdtc À , as well as the complexes [Cu 2 -(tpmc)](ClO 4 ) 4 and [Cu(tpmc)](ClO 4 ) 2 ·2H 2 O were studied in aqueous NaClO 4 and HClO 4 solutions by cyclic voltammetry on glassy carbon electrode. The electrochemical properties of the ligands and Cu(II) complexes were correlated with their electronic structure. Conductometric experiments showed different stoichiometry in complexation of tpmc with Cu 2 + ions and transport of ions in acetonitrile and in aqueous media. These studies clarified the application of this macrocyclic ligand as ionophore in a PVC membrane copper(II) selective electrode and contributed elucidation of its sensor properties.
Electrochemistry of cobalt ethylenediamine complexes at high pH
Journal of the Serbian Chemical Society, 2015
The electrochemical behavior of cobalt ethylenediamine complexes (Co(en)), at pH 12 was investigated by cyclic voltammetry (CV), the potentiostatic pulse technique and polarization curve measurements at stationary and rotating glassy carbon (GC) electrodes. It was shown that sixteen different species could be formed in a solution containing Co(en) 3 , with the most stable one at all pH values being [Co(en) 3 ] 3+. The reduction of [Co(en) 3 ] 3+ into [Co(en) 3 ] 2+ was shown to be a totally irreversible, one-electron exchange reaction. Further reduction of [Co(en) 3 ] 2+ was found to be a complex process leading to cobalt deposition at potentials more negative than-1.45 V vs. SCE. The process of [Co(en) 3 ] 2+ oxidation was also complex and most probably coupled with chemical reactions. Keywords: distribution of Co(en) 3-based complexes; irreversible reduction of [Co(en) 3 ] 3+ /[Co(en) 3 ] 2+ ; reduction of [Co(en) 3 ] 2+ to Co.
mechanism and cyclic voltammetry of Cu(en)2X2.nH2O complexes in Some Nonaqueous Solvents
The electrochemical studies of solid 2.0X10-3 M Cu(en)2X2.nH2O (n=o for X=ClO4-, NO3-, SCN- and n=1 for Br-) in dimethylsulfoxide, acetonitrile, dimethylformamide /0.1 Mtetrabuthylammoniumperchlorate, have been carried out by cyclic voltammetry. The electrode process shows two elctrreduction and two chemical steps (CECE) mechanism. The reduction potentials of Cu(en)2(ClO4)2 shift in the order DMF DMSO AN contrary to one's expectation. For Cu(en)2(NO3)2 and Cu(en)2(SCN)2 , the reduction potentials are more negative to DMF as expected. IN DMF, the reduction potential Epc1 shift anodically in the order Cu(en)2(ClO4)2 Cu(en)2(NO3) Cu(en)2(SCN)2 indicating that EPc1 is also dependent on the nature of anion X.
CERN European Organization for Nuclear Research - Zenodo, 2012
Four new mixed-ligand copper(n) complexes involving 6-chloronicotinic acid (6-CINA) and aromatic diimines and one binary Cu 11 complex with 5,5'-Me 2 bipy have been synthesized in aqueous/nonaqueous media. Elemental analyses (Cu, C, H, N%), molar conductance, spectral (FT-IR, UV-Visible) and room temperature magnetic susceptibility measurements have been used for structural characterization of these complexes. FT-IR spectra of these complexes indicate the bidentate mode of coordination through carboxylate oxygen atoms of 6-chloronicotinate anion. On the basis of these measurements the following formulae have been proposed : ICu(6-CINA)(bipy)(H 2 0)](N0 3) (1), [Cu(6-CINA)(5,5'-Me2bipy)(ON02)](H20) (2), [Cu(6-CINA)(phen)(H 2 0)](N0 3) (3), [Cu(6-CINA)(dmp)(ON0 2)](H 2 0) 4 and [Cu(5,5'-Mezbipy)z](CI04)2 (5), {where diimines = 2,2'-bipyridine (bipy); 5,5'-dimethyl-2,2'-bipyridine (5,5'-Me 2 bipy); 1,10phenanthroline (phen) and 2,9-dimethyl-1,10-phenanthroline (dmp)}. The observed room temperature (300 K) magnetic moments (IJ.err = I. 70 to 1.84 B.M.) correspond to mononuclear complexes with one unpaired electron. The distorted square-pyramidal coordination geometry around the Cu 11 ion has been proposed in solid complexes 1-4. In DMSO and DMF solutions, these COI~plexes possess distorted octahedral geometry due to solvent coordination. The electrochemical behaviors of these complexes have also been studied at a glassy carbon working electrode (GCE) in DMSO and DMF media containing 0.2 M NaCI04 as the supporting electrolyte using cyclic voltammetry. The electrochemical behavior of complex 4 involving dmp as the auxiliary ligand is different from rest of the three mixed-ligand Cull complexes.
Cyclic voltammetric studies of some bis (phenanthrolines )copper (II) complexes
2007
The electrochemical properties of some bis(phenanthrolines)copper(II) complexes, [Cu(NN) 2 ](ClO 4 ) 2 (NN denotes 1,10-phenanthroline (phen); 4,7-diphenyl-1,10-phenanthroline (bathophen); 2,9-dimethyl-1,10-phenanthroline (dmp) and 2,9-diphenyl-1,10-phenanthroline (dpp) have been studied by cyclic voltammetry at a platinum working electrode in dimethyl sulfoxide (DMSO) and dimethyl formamide (DMF) containing 0.1 M tetrabutyl ammonium perchlorate (TBAP) as the supporting electrolyte. All these complexes display a quasireversible Cu 2+/+ redox couple. Both the electron-donating methyl groups and electron-withdrawing phenyl groups at the 2,9-positions of the phen ligand elevate the Cu 2+/+ redox potentials of the [Cu(dmp) 2 ](ClO 4 ) 2 and [Cu(dpp) 2 ](ClO 4 ) 2 complexes. The redox potentials of [Cu(dmp) 2 ] 2+ are nearly 50 mV more positive than that of [Cu(dpp) 2 )] 2+ in a given solvent. It is found that the Cu 2+/+ reduction potential (E pc ) as well as formal potential (E 0' ...
Electrochemical studies of copper(II) complexes with Schiff-base ligands
Polyhedron, 2002
The electrochemical reduction of copper(II) complexes with salen Schiff-base ligands derived from ethylenediamine or (R,R) or (S,S)-1,2-diphenylethylenediamine and 5-methoxy, 5-bromo and 5-nitrosalicylaldehyde have been studied by cyclic voltammetry in the potential range +1 to − 2.3 V in dimethyl sulfoxide (DMSO) as a solvent. The resulting voltammograms consist of a single quasi-reversible one-electron transfer attributable to the couple [Cu(II)L]/[Cu(I)L] − . Trends in cathodic peak potential (E pc ) values are observed which can be correlated with the electronic effects of the 5-substituents of the Schiff-base ligands. Changes in the basicity of the ligand groups are determinant for such electrochemical trends.