Synthesis and electrochemical study of some novel alkynylferrocene derivatives

Ferrocene and their derivatives are well-known redox active materials and were extensively used by construction of modified electrodes for the design of electrochemical sensors and biosensors. Substituent derivatization of ferrocene offers the prospect of controlling ferrocene moiety properties such as solubility, stability, reversibility of oxidation wave (important for their role as an electron transfer mediator) and oxidation potential, which is critical in the electrochemical determination of biological compounds. A new series of rigid alkynylferrocene including of 2-ferrocenylethynyl fluoren (3a), 2-ferrocenylethynyl fluoren-9-one (3b), 4-ferrocenylethynyl aniline (3c) and 3-ferrocenylethynyl-1-trifluoromethyl benzene (3d) have been prepared in good yields by Sonogashira coupling reaction. All products were characterized by 1H and 13C NMR, FT-IR, and elemental analysis. The redox chemistry of these compounds has been investigated by cyclic voltammetry. The half-wave potential of the terminal ferrocenyl moieties increases progressively in the order of 3c < 3a < 3b < 3d, which is consistent with the electron density on the ferrocenyl unit.