Electrochemical investigations of some newly synthesized arylazapyrazole derivatives (original) (raw)

Monatshefte für Chemie - Chemical Monthly, 2016

Abstract

Three derivatives of arylazapyrazole ((E)-4-(phenyldiazenyl)-3,5-dimethyl-1H-pyrazole, (E)-4-[(4-fluorophenyl)diazenyl]-3,5-dimethyl-1H-pyrazole, and (E)-4-[(4-iodophenyl)diazenyl]-3,5-dimethyl-1H-pyrazole) were synthesized, characterized, and further investigated for their electrochemical behavior at glassy carbon electrode using cyclic voltammetry. All compounds were reduced following Ei Ci mechanism giving single cathodic peak in potential range 0 to −2 V vs. Ag/AgCl. The plots of log iP vs. log ν showed that the electrode process is mixed adsorption-diffusion controlled. The kinetic parameters such as transfer coefficient (αn), diffusion coefficients (Do), and standard heterogeneous rate constants (ks) were determined from the electrochemical data. The values of Do were determined and found greater for the smallest among the three compounds. ks values were calculated by Laviron formalism which lies in the order of 10−2 s−1. Temperature and pH effects were studied and thermodynamic parameters such as change in free energy of activation (ΔG#), apparent activation energy (Ea), enthalpy (ΔH#), and entropy (ΔS#) of activation were determined. Negative values of Ea, ΔH#, and ΔS# imply that the electrode process needs lesser over potential with temperature rise, pre-adsorption of the analyte onto the electrode surface and the activated complex has a more organized structure than the reactants, respectively.Graphical abstract

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