A triazole tethered triferrocene derivative as a selective chemosensor for mercury(II) in aqueous environment

The synthesis, electrochemical, optical and cation-sensing properties of two triazole tethered ferrocene derivatives, C₂₅H₂₅ON₃Fe₂, 2 and C₄₀H₄₀O₂N₆Fe₃, 3 are presented. The solid state structure of compound 2 has been established by X-ray diffraction analysis which reveals that the unit cell of molecule 2 consists of 3-D helical chain formed via CH⋯N interaction and π⋯π stacking. The complexation properties of the receptors can be inferred either from redox shift or visual output response (colorimetric) for Hg²⁺ and Cu²⁺ cations. The common structural feature of these ligands is the presence of other ferrocene moiety as redox unit. Interestingly, the redox and colorimetric responses, towards Hg²⁺ are preserved in the presence of water (CH₃CN/H₂O, 2/8), which can be used for the selective colorimetric detection of Hg²⁺ in aqueous environment over other competitor cations. The changes in the absorption spectra are accompanied by the appearance of a new low energy (LE) peak at ca. 626 nm for 2 and 632 nm for 3 (2: ε = 669 M⁻¹ cm⁻¹ and 3: ε = 1150 M⁻¹ cm⁻¹), due to the change in color from yellow to purple for Hg2+ cations in CH₃CN/H₂O (2:8)