Controlling Charged State Colors in Triphenylamine‐Based Anodically Coloring Electrochromes

Abstract

AbstractA series of anodically coloring electrochromic molecules comprised of thioalkyl‐substituted 3,4‐ethylenedioxythiophenes coupled to triphenylamine units that vary in position and degree of electron rich character of the substituents are reported, which influences the molecules geometric, electrochemical, optoelectronic, and excited‐state properties. Their redox properties are evaluated and it is discovered that modulation of both the first and second oxidation potential, formation of the cation radical, and dication respectively, can be varied from 0.03 to 0.18 V and 0.32 to 0.46 V versus Fc/Fc+ respectively. For the first time in ACE‐based molecular systems, the ability to vary the electrochemical potential separation between successive charge states is demonstrated, which directly influences the generation of color. The chemical oxidant, ferric triflate, is used to visualize the vibrantly colored cation radical solutions at 1 equivalent, followed by a second equivalent that opens a new and differing color palette for the dication state. Optical transitions are probed during electrochemical oxidation using an optically transparent thin layer electrode demonstrating selective control in generating successive charge states. Density functional theory simulations are used to analyze the excited state and elucidate how substituent identity affects the neutral, cation radical, and dication optical transitions, and thereby the resulting color.