Electrochromic materials based on surface-confined terpyridine assemblies prepared via click chemistry

In this work, we propose a methodology to create electrochromic materials (ECMs) using an on-surface click chemistry approach. We demonstrate that the click reaction between azide-terminated on-surface siloxane template ((4-azidophenyl)- or (4-(azidomethyl)phenyl)- siloxane layers) and the electrochromic (EC) molecular unit bearing accessible triple bonds, (bis-4'-(4-ethynyl-phenyl)-2,2':6′,2″-terpyridine) iron (II) complex), allows for an effective covalent embedding of well-defined molecular EC units into the porous conductive indium tin oxide (ITO) support. We show that minor structural modifications of the molecular moieties of the templating layer result in notable changes in the packing densities of the molecules on the surface of the support and significantly affect the performance and stability of the resulting EC materials. In more detail, the presence of only one additional CH 2 unit in the templating layer results in higher packing density on the surface. Resulting EC devices demonstrate rapid switching times on par with ED devices that utilize similar terpyridine-based EC moieties attached to the templating layer via N-alkylation and overall better long-term cycling durability. The click approach enables the construction of diverse EC molecular architectures, facilitating precise structural design and property tuning. We believe that the presented methodology holds significant promise for developing a broad range of novel EC materials. SYNOPSIS TOC (Word Style “SN_Synopsis_TOC”). If you are submitting your paper to a journal that requires a synopsis graphic and/or synopsis paragraph, see the Instructions for Authors on the journal's homepage for a description of what needs to be provided and for the size requirements of the artwork. • Click chemistry on the surface to create covalently embedded electrochromic monolayers. • Surface-confined metal-organic monolayers on high-surface-area conductive screen-printed electrodes. • The surface-confined nature of the materials supports long-term cycling durability and enhances electron transfer • Precise control over materials' properties by tuning the structure of the surface-confined EC moieties.