In Situ Film Growth of Metallosupramolecular Polymer via Electropolymerization and Its Application as Electrochromic Film

Abstract

Electropolymerization is an important technique for surface functionalization, owing to its convenient and controlled synthetic pathways. The in situ synthesis of metallosupramolecular polymers (MSPs) utilizing coordination-driven metal ions and coordinating ligands as well as studying their potential applications using electropolymerization have been less explored. Herein, we demonstrated the formation of MSPs on a preterpyridinefunctionalized indium tin oxide (ITO) glass substrate by using Fe(III) ions and 4′,4⁗-(1,4-phenylene)-bis(2,2′:6′,2″-terpyridine) ligand. By providing an anodic potential, polymer growth occurred due to the strong coordination between the reduced metal ions (Fe(II)) and the bis-terpyridine ligand. The formation of the polymer was evident from the growth of the corresponding peaks in the cyclic voltammogram and UV−vis spectral profile. The surface morphology was characterized by using atomic force microscopy (AFM). The electrochromic (EC) properties of the electropolymerized MSP (EP-MSP) were studied by utilizing the metal-to-ligand charge-transfer color band of the redox-active Fe(II)-(terpyridine) 2 unit present in the MSP backbone. It was observed that the film exhibited an optical switching coloring time of 2.1 and 5.7 s for bleaching, a transmittance change of 54%, and a coloration efficiency of 142.6 cm 2 C −1 .