ELECTROCEMICAL STUDY OF SYM. POLYMETHYLFERROCENE/SYM. POLYMETHYLFERRICINIUM (MenFc/MenFc+) (n = 6, 8, 10) REDOX SYSTEMS IN ORGANIC SOLUTIONS

Redox systems MenFc/MenFc+ (n=6, 8, 10) consisting of symmetric polymethylferrocene and the corres-pon¬ding polymethylferricinium cation have been studied by cyclic voltammetry in organic solvents - acetonitrile, dichloromethane and dimethylsulfoxide. The values of the diffusion coefficient of the reagents (MenFc and MenFc+) of redox systems have been calculated by the Randles-Sevcik equation, which are consistent with the conclusion that "a one-electron reversible electrochemical reaction is determined by the diffusion of the reagents". The features of the change in the values of the diffusion coefficient, both in the sequence of Fc/Fc+→Me6Fc/Me6Fc+→ Me8Fc/Me8Fc+ → Me10Fc/Me10Fc+ redox systems and in dependence on the presence or absence of the charge in the reagents, have been interpreted by the change in the volume (dimensions) of the reagents with increasing number of methyl groups and the interaction of polymethylferricinium cations with electrolyte anions in solution.The fact that the diffusion coefficient of the cation in each MenFc/MenFc+ redox system is very close to the diffusion coefficient of the molecule, which allows us to replace the standard electrode potential (Eo) of the system with the half-wave potential (E1/2) according to the Nernst equation. The effect of the nature of the solvent on the value of the half-wave potential of these redox systems has been studied. It has been shown that the appearance of methyl groups in cyclopentadienyl rings significantly weakens the interaction of reagents (especially the iron atom) with solvent molecules, in comparison with the interaction in the Fc/Fc+ system and, as a result, their half-wave potential is less affected by the surrounding medium – solvent molecules and electrolyte ions