Redox processes in the solution of Ni(II) complex with salen type ligand and in the polymer films

Abstract The investigations of oxidation processes of (±)-trans-N,N′-bis(3,5-di-methylsalicylidene)-1,2-cyclohexanediaminenickel(II)) [Ni(salcn(2Me))] and ligands with Me substituents attached in o- (H2salcn(Me)) or o- and p-positions (H2salcn(2Me)) in CH2Cl2 were performed by CV, exhaustive electrolysis, UV VIS NIR and IR methods. H2salcn(Me) and H2salcn(2Me) are irreversibly oxidized to phenoxyl radicals and bis-phenoxyl radicals. The hydrogen bonds stabilize both forms of the oxidized ligands. [Ni(salcn(2Me))] is oxidized in three steps. The overall process involves ligand and partially nickel ion. In the I step, [Ni(salcn(2Me))] is oxidized to phenoxyl radical complex, which is well stabilized by the nickel ion. In the II step the oxidation is realized by forming bis-phenoxyl radicals and phenoxonium cations complexes. The films derived from salen complexes deposited on the Pt electrode surface ( poly [Ni(salcn)], poly [Ni(salcn(Me))], poly [Ni(salcn(Bu))]) were obtained as a result of anodic electropolymerization processes. On the basis of FTIR ATR spectroscopy and CV experiments, the relationship of the polymer films structures, charge transport and the potential range of the applied electrosynthesis was shown.