13408-72-5Relevant articles and documents
Spectroscopic and electrochemical study of the adsorption of [Co(en) 2Cl2]Cl on γ-alumina: Influence of the alumina ligand on Co(III)/(II) redox potential
Vivier, Vincent,Aguey, Francois,Fournier, Jeanine,Lambert, Jean-Francois,Bedioui, Fethi,Che, Michel
, p. 900 - 906 (2006)
UV-visible and Raman spectroscopies as well as electrochemical techniques have been used to characterize cis- and trans-[Co(III)(en) 2Cl2]Cl (en = ethylenediamine) complexes and the γ-alumina-supported cis-Co(III) complex. It is shown that the electrochemical reduction of these complexes occurs according to a multistage mechanism involving two electrochemical steps, with the formation of a dimer that was characterized by UV-visible spectroscopy (intervalence band at 670 nm). The apparent standard redox potential for each step has been determined, and experimental results reveal that cis and trans complexes present similar electrochemical characteristics. It is also shown that the deposition of trans-[Co(III)(en)2Cl2]+ on γ-alumina leads to an inner-sphere complex (ISC) in a cis configuration in which Cl- ligands are substituted by OH or O- surface groups of alumina. These changes in the coordination sphere of the complex induce a substantial decrease of its apparent redox potential since it is -0.63 V/SCE (saturated calomel electrode) for the γ-alumina-supported cis-Co(III) complex, whereas values of -0.17 and -0.35 V/SCE were determined in dimethyl sulfoxide (DMSO) for the trans and cis precursor complexes, respectively.
Kinetics of the oxidation of L-cysteine by trans- and cis-cobalt(III) and iron(III) complexes
Abdel-Halim, Hamzeh M.,Abu-Surrah, Adnan S.,Baker, Hutaf M.
, p. 1346 - 1350 (2006)
Kinetics of oxidation of L-cysteine by pairs of trans and racemic cis isomers of cobalt(III) and iron(III) based transition metal complexes have been studied in aqueous solution. Kinetics measurements were run under pseudo first order conditions in which the concentration of cysteine is between one and two orders of magnitude greater than that of the isomers of the transition metal complex. The orders of the reaction with respect to both cysteine and the isomer were determined. The observed rate constants and the overall rate constants of the oxidation process were measured. For all geometrical isomers, it was found that the rate constant of oxidation of L-cysteine by the trans isomer is between one to three orders of magnitude greater than that by the CM isomer. The difference in rates can be explained by a geometric factor around the metal ion center in the complex. The less crowded isomer (trans) makes electron transfer easier and hence facilitates the oxidation process which leads to a higher oxidation rate.
Kinetic analyis of TF data, XXXV. Spectroscopic and thermal studies of some cobalt(III) chelates with ethylenediamine
Zsako,Pokol,Novak,Varhelyi,Dobo,Liptay
, p. 843 - 856 (2001)
A number of 30 [Co(en)3]Y3, [Co(en)2X2]Y and [Co(en)2X(amine)]Y2 type complexes (X=Cl, Br; Y=Cl, Br, I, NCO, NCS, NO3, ClO4, etc.; amine=aromatic and alkylamines) were obtained from trans-[Co(en)2Cl2]Cl by double decomposition and by substitution reactions, respectively. The structure of the complexes was proved by means of far and middle FTIR spectra. The thermal decomposition was studied by TG, DTA and DSC measurements. Mass spectra were also recorded. In the case of [Co(en)3]Y3 complexes the nitrate, perchlorate and dimesoperiodates decompose suddenly, frequently explosion like. The halides and thiocyanates seem to substitute an ethylenediamine ligand, yielding a rather unstable intermediate. The pyrolysis of [Co(en)2X2]Y type derivatives yields no relatively stable intermediates, but the decomposition temperatures may be correlated with the nature of Y and with the cis or trans configuration of the compound. With the [Co(en)2X(amine)]Y2 type complexes one observes the formation of [Co(en)2XY]Y as intermediate product. From the TG curves kinetic parameters were derived for some dehydration and deamination processes, by using the nomogram method. The validity of a nonlinear kinetic compensation law was observed.
Temperature programmed decomposition of cobalt ethylene diamine complexes
Dash,Ajikumar,Kamruddin,Tyagi
, p. 141 - 148 (2008/10/09)
The cobalt co-ordination complexes, [Co(en)2Cl2]Cl and [Co(en)2CO3]Cl, synthesised through literature procedures, were characterised by FTIR. Trace metallic impurities were determined by ICP-MS. Crystallinity of the samples were ascertained by preliminary X-ray powder diffraction analysis. Dark field polarised optical microscopy (OM) was used to observe particle size distribution. These compounds were subjected to temperature programmed decomposition (TPD) in thermogravimetric analyser (TGA). TPD was also carried out in a home built mass spectrometry based evolved gas analyser (EGA-MS). The complex TGA weight loss profile could be successfully explained through EGA data. Complimentary information received from both the above techniques indicated sequential decomposition, prevalence of steric effect and functional group ejection. The non-isothermal kinetic analysis of TGA and EGA data showed dominance of kinetic control mechanisms based on sigmoidal rate laws like Avarami-Erofeev (AE) and random nucleation (RN). The fraction release α ~ T plots were used to evaluate integral model function g(α) of non-isothermal kinetic rate expressions. From log[g(α)/T2] ~ 1/T plots of well correlated model functions, Arrhenius parameters like activation energy and pre-exponential factors were evaluated for various decomposition steps.
