Electrochemical behaviour of tetraazamacrocyclic nickel(II) complexes functionalized with crown ethers

Ni(II) and Co(III) complexes of 5-methyl-1,3,4-thiadiazole-2-thiol: syntheses, spectral, structural, thermal analysis, and DFT calculation

“…The cyclic voltammograms were obtained at a mercury electrode using 0.1 M KCl as supporting electrolyte in the potential range of −1.0-1.0 V with a scan rate of 100 mVs −1 and show the quasi-reversible and irreversible redox behavior of 1 and 2, respectively. Complex 1 exhibits cathodic and anodic peak potentials at 0.510 and 0.326 V, respectively, and the separation between the cathodic and anodic peak potentials (ΔE p = E pa − E pc ) of 0.184 V indicates a quasi-reversible redox process assignable to the nickel(II)/ nickel(III) couple with the formal redox potential E = (E pa + E pc )/2 = 0.418 V [37]. Complex 2 exhibits cathodic and anodic peak potentials at 0.488 and −0.526 V, respectively, and the separation (ΔE p = E pa − E pc ) of 1.014 V indicates an irreversible redox process assignable to the Co (III)/ Co(II) couple with the formal redox potential E = (E pa + E pc )/2 = 0.019 V. However, it is to be noted that the peak separation (ΔE p = E pa − E pc ) is somewhat high as compared to that expected for one-electron process and hence it can be concluded that the redox process is coupled with some chemical reaction.…”