Ferrocene- and ruthenocene-containing chalcones: A spectroscopic and electrochemical study

Chalcones of the type Mc-CO-CHCH-Ph, Ph-CO-CHCH-Mc and Mc-CO-CHCH-Mc with Mc = Fc = ferrocenyl or Rc = ruthenocenyl, and Ph = phenyl were synthesized. Synthesis was achieved by base catalyzed Claisen-Schmidt condensation of the appropriated acetyl and aldehyde in ethanol. Cyclic voltammetry in CH₃CN in the presence of 0.1 mol dm⁻³ N(Bu)₄]PF₆] revealed chemical and electrochemical reversible behaviour for the Fc/Fc⁺ couple and irreversible electrochemistry for the two electron Rc/Rc²⁺ couple. The potential ranges for the Fc/Fc⁺ couple varied in the range 138 ? E°′ ? 302 mV while E_pa for Rc/Rc²⁺ couple was between 358 and 510 mV vs. FcH/FcH⁺, the internal standard. Chalcones with the carbonyl group adjacent to the metallocene, are more difficult to oxidize.