Synthesis, Structural Charaterization, and Electrochemical and Optical Properties of Ferrocene–Triazole–Pyridine Triads

The synthesis and electrochemical, optical, and cation-sensing properties of the ferrocene–triazole–pyridine triads 3 and 5 are presented. Azidoferrocene 1 and 1,1′-diazidoferrocene 4 underwent the “click” reaction with 2-ethynylpyridine to give the triads 3 and 5 in 81% and 68% yield, respectively. Electrochemical studies carried out in CH3CN in the presence of increasing amounts of Zn2+, Ni2+, Cd2+, Hg2+, and Pb2+ metal cations, showed that the wave corresponding to the ferrocene/ferrocenium redox couple is anodically shifted by 70–130 mV for triad 3 and 167–214 mV for triad 5. The maximum shift of the ferrocene oxidation wave was found for 5 in the presence of Zn2+. In addition, the low-energy band of the absorption spectra of 3 and 5 are red-shifted (Δλ = 5–10 nm) upon complexation with these metal cations. The crystal structures of compounds 3 and 5 and the complex [32·Zn]2+ have been determined by single-crystal X-ray methods. 1H NMR studies as well as density functional theory calculations have been carried out to get information about the binding sites that are involved in the complexation process.