Electrooxidation of the calix[4]arenedihydroquinone mechanistic investigation and electrodeposition of the oxidised form on platinum grid

Abstract

The electrochemical behaviour of 5,17-di-tert-butyl-11,23,25,27-di-dihydroxy-26,28-dimethoxy calix[4]arene has been investigated at a platinum electrode in aprotic solvent by cyclic, square wave and rotating-disk voltammetry as well as by controlled potential coulometry. By comparing to the ferrocene, the height of the first irreversible transfer process involves only one-electron transfer, which corresponds to the formation of the radical cation. However, the last substance undergoes a fast chemical reaction and follows an ECHE sequence. But, the large scale electrolysis at the first anodic peak required a consumption of 2.25 Faradays per molecule. When we interrupt the electrolysis after consumption of 1 Faraday per molecule, an intermediate compound was formed, which is the calix[4]arenequinhydrone (X4Me2(H2Q)Q) through a partial reduction of the start product. Furthermore, the reaction may evolves in solution following an ECHECH redox process for generating the calix[4]arenediquinone (X4Me2Q2). On the other hand, the voltammetric follow-up shows the electrogeneration to the departure product during the macroscale electrolysis according an ECHE-disproportionation mechanism. When the electrolysis was performed after the third oxidation peak, (X4Me2Q2) was electrogenerated in solution and was deposit, afterward, on the platinum grid.