Asymmetrically substituted ferrocene derivatives showing redox switching of optical properties

The electrochemical and spectroelectrochemical behaviors of three ferrocene derivatives, (1) (C₁₈H₃₇)₂NC₆H₄CHCHFcCH₂OH, (2) (C₁₈H₃₇)₂NC₆H₄CHCHFcCHO, (3) (C₁₈H₃₇)₂NC₆H₄CHCHFcCHC(CN)₂, were studied and analyzed on basis of frontier orbital interactions. It was shown that all the three derivatives show two oxidation steps. The first oxidized states of 1 and 2 are stable and show strong LMCT (ligand-to-metal charge transfer) bands. This suggests that they may serve as redox switching of optical properties. In contrast, the first oxidized state of 3 becomes unstable due to strong electron-withdrawing effect of the acceptor substitute.