Complexes [Ni(3-NO2SalEn)] and [Ni(3-NO2SaltmEn)] were synthesized and identified, and polymers based on them were obtained. It was found with the help of voltammetry that the introduction of nitro groups in the complexes shifts their redox activity in the direction of positive potentials; it was shown by in situ quartz microgravimetry and in situ absorption spectroscopy methods that fragments of the polymer complexes under study can undergo reversible two-electron oxidation at the expense of formation of polarons and bipolarons in the ligand surrounding.