Electrochemical properties of 1-(o-, m-, p-nitrophenyl)-3-(m-nitrophenyl)- 5-phenylformazans and their nickel complexes


Abstract: The electrochemical properties of NO_2 formazans and their Ni(II) complexes were investigated. The investigated formazans included a NO_2 group at the o-, m-, and p-positions of the 1-phenyl ring and at the m-position of the 3-phenyl ring. The oxidation and reduction peak potentials, number of electrons transferred, diffusion coefficient, heterogeneous rate constant, and possible reaction mechanism of the compounds were determined with the use of cyclic voltammetry (CV), ultramicrodisc electrodes (UMEs), and chronoamperometry (CA). The peak potentials (E}_{ox1}) were observed to shift towards more anodic potentials in formazans and more cathodic potentials in their respective Ni complexes compared to unsubstituted compounds. There was a correlation between their absorption and electrochemical properties. The electrochemical reaction mechanism was observed to be dependent upon the type and position of the substituent in the structure. Nicholson and Shain criteria showed that the reaction follows an EC mechanism.

Keywords: Formazans, nickel complexes, spectroscopy, substituent effect, cyclic voltammetry, ultramicrodisc electrode.

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