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New Design Paradigm for Color Control in Anodically Coloring Electrochromic Molecules

Christiansen, Dylan T., Tomlinson, Aimée L., Reynolds, John R.
Journal of the American Chemical Society 2019 v.141 no.9 pp. 3859-3862
absorption, cations, color, energy
A new paradigm is established for the design of conjugated anodically coloring electrochromic molecules. It is shown that through crossconjugation the electronic energy levels of the radical cation state may be controllably tuned independent of the neutral state. It is shown how cross-conjugation can be used to tune the radical cation state independent of the neutral state. Manipulating the oscillator strengths of radical cation transitions allows for tuning of the color by shifting the λₘₐₓ of the low-energy absorption by over 400 nm. The neutral states of these molecules are UV absorbing, providing solutions that are colorless with L*a*b* values of 100, 0, 0. They are oxidized to vibrantly colored radical cations with absorptions that span the visible spectrum, creating green, yellow, and red chromophores. These molecules are then mixed to create transmissive, colorless blends that switch to opaque black solutions.