Covalently linked ferrocenyl quinones: Proton-dependent redox behavior and charge redistribution

The proton-dependent redox chemistry of dyads comprised of a ferrocenyl electron donor directly linked to a hydroquinonyl electron donor or to a quinone electron acceptor by a single covalent bond has been characterized. Ferrocenyl-1,4-hydroquinone (2), ferrocenyl-1,4-benzoquinone (3), 3-ferrocenyl-1,2-catechol (5), and the precursors ferrocenyl-1,4-dimethoxybenzene (1) and 3-ferrocenyl-1,2-dimethoxybenzene (4) were studied; also the unstable compound 3-ferrocenyl-1,2-benzoquinone (6) was observed in the spectroelectrochemistry of 5. Detailed cyclic voltammetry, coulommetry, and UV-vis-NIR spectroelectrochemistry experiments allied with EPR, NMR, and Mossbauer spectroscopy were used to probe the pH-dependent redox chemistry and electron distribution within the compounds.