Ferrocenyl‐Containing Fe(II)‐Bipyridinedicarboxamide Polysiloxane Complexes With Multiredox Activity

Abstract

Ferrocenyl‐containing Fe(II)‐bipyridinedicarboxamide polysiloxane complexes with two redox metal centers were obtained by anionic ring‐opening polymerization, polycondensation, and complexation reactions utilizing various FeII:Bipy molar ratios of 1:(3–12). The polymer ligand was characterized by liquid‐state NMR, FTIR, and gel permeation chromatography (Mn = 8800). The structure of the polymer‐metal complexes (PMCs), that is, the presence of ferrocenyl groups and [FeII(Bipy)3] coordination cross‐links with FeII–NBipy bond formation, was confirmed by solid‐state NMR, FTIR, UV–vis, and EDX. The PMCs exhibit multiredox activity showing three redox waves at E1/2 ≈ −1.3, 0.2, and 1.0 V related to Fc/Fc+ couple, [Fe(Bipy)2]+/[FeII(Bipy)3]2+, and [Fe(Bipy)3]2+/[Fe(Bipy)3]3+ transformations. The PMCs possess electrochromic properties resulting from the reduction–oxidation of ferrocenyl (Fc/Fc+) and [FeII(Bipy)3] fragments and leading to changes in intensity of bands at 628, 542, and 380 nm in the UV–vis spectra (coloring efficiency reaches 13.4 cm2·C−1). The PMCs are flexible, stretchable, and mechanically strong silicone materials with elongation at break, tensile strength, and Young's modulus reaching 110%, 3.5 MPa, and 21.8 MPa, respectively, with self‐healing ability at 100°C. The described properties expand applications of PMCs as multiredox materials in polymer engineering for fabrication of (opto)electronic devices and protective coatings with a long service life compared to previously reported multiredox polymers.