Dual-mode electrochromism switched by proton transfer: dynamic redox properties of bis(diarylmethylenium)-type dyesElectronic supplementary information (ESI) available: spectral data for new compounds. See http://www.rsc.org/suppdata/cc/b1/b104742f/

Abstract

Upon oxidative dimerization of pale yellow Ar₂CCHPh 1 (Ar = 4-Me₂NC₆H₄), deep blue 1,4-dication 2²⁺ was obtained as a stable salt, which was transformed into 1 by reductive C–C bond fission; deprotonation of 2²⁺ gave intense yellow diene 3, which was interconvertible with violet dication 4²⁺ by two-electron transfer, thus exhibiting two distinct modes of electrochromism before and after proton transfer.