Synthesis of Metallo-Supramolecular Polymers with Bis-NNN-Tridentate Ligand for Electrochromic Devices

A bis-tridentate ligand with 2,6-bis(phenylamide)pyridine moieties (L1) was synthesized by amidation and Suzuki-Miyaura cross coupling reaction from chelidamic acid monohydrate. Novel metallo-supramolecular polymers containing iron(II), ruthenium(II), or nickel(II) ions (PolyFeL1, PolyRuL1 and PolyNiL1, respectively) were obtained as yellowish brown solid via complexation of L1 with the metal ions in the presence of a strong base. The polymers were characterized by IR, UV-vis-NIR absorption spectra, and cyclic voltammetry (CV). The IR spectra showed disappearance of NH stretching peak and shift of C=O stretching peak due to the complexation. The characteristic LMCT absorption appeared at 470 (Fe), 442 (Ru), or 367 (Ni) nm. The solution of the polymers showed a reversible redox wave attributed to the redox of metal ions. PolyFeL1 exhibited reversible electrochromism between orange and brown by applying + 3 V or 0 V.