Tailoring Valence Tautomerism by Using Redox Potentials: Studies on Ferrocene‐Based Triarylmethylium Dyes with Electron‐Poor Fluorenylium and Thioxanthylium Acceptors

Three new electrochromic ferrocenyl triarylmethylium dyes with fluorenylium (1 a+, 1 b+) or thioxanthylium c+) residues were selected in order to keep the intrinsic differences of redox potentials for ferrocene oxidation and reduction small trigger valence tautomerism (VT). UV/Vis/NIR quantitative EPR spectroscopy identified paramagnetic diradical isomers a..+–1 c..+ alongside diamagnetic forms a+–1 c+, which renders these complexes magnetochemical switches. The as well one-electron-reduced triarylmethyl found dimerize solution. For radical a., dimerization occurs on timescale cyclic voltammetry; this allowed us determine kinetics equilibrium constant process by digital simulation. Mößbauer indicated that a+ b+ retain VT even solid state. spectro-electrochemistry revealed poly-electrochromic behaviour establishing distinctly different electronic absorption profiles corresponding oxidized reduced forms.