Metallo-Macrocycle Camouflages: Multicolored Electrochromism in a Fe(II) Based Metallo-Supramolecular Macrocycle Utilizing the Redox of Metal Centers and Carbazole Containing Ligand

Herein, a carbazole containing bis-terpyridine based angular ditopic ligand was synthesized to prepare a pentameric metallo-supramolecular macrocycle (Fe-Cz-MC) with Fe(II) ions. Fe-Cz-MC was exclusively characterized by spectroscopic, structural, and morphological characterization techniques. The deliberate insertion of redox-active carbazole moieties with hexyl groups along with redox of Fe(II) gives rise to a multicolored electrochromic material with adequate amorphous nature for good film-forming ability. The Fe-Cz-MC film, dipping in electrolyte solution, shows fast and stable electrochromic switching from pristine purple, brown to yellow reliant on the oxidation of Fe(II) and carbazole centers in a potential window of 0–2 V. The fabricated solid-state electrochromic device with Fe-Cz-MC also exhibits similar multicolor electrochromism with fast coloration time (tc), and bleaching times (tb) of 2.45 and 3.49 s, respectively, along with a coloration efficiency of 316.17 cm2 C−1 and cycle stability over 1000 cycles. The present work can provide a viable strategy to utilize redox of both metal and organic ligand in a metallo-macrocycle to exhibit multicolored electrochromism.