A highly selective redox, chromogenic, and fluorescent chemosensor for Hg²⁺ in aqueous solution based on ferrocene–glycine bioconjugates

Abstract

The synthesis, electrochemical, optical, and metal-cation-sensing properties of ferrocene–glycine conjugates C₃₀H₃₈O₈N₈Fe (2) and C₂₀H₂₄O₄N₄Fe (3) have been documented. Both compounds 2 and 3 behave as very selective redox (ΔE_1/2 = 217 mV for 2 and ΔE_1/2 = 160 mV for 3), chromogenic, and fluorescent chemosensors for Hg²⁺ cations in an aqueous environment. The considerable changes in their absorption spectra are accompanied by the appearance of a new low-energy peak at 630 nm (2, ε = 1600 M^–1cm^–1; 3, ε = 822 M^–1cm^–1). This is also accompanied by a strong color change from yellow to purple, which allows a prospective for the “naked eye” detection of Hg²⁺ cations. These chemosensors present immense brightness and fluorescence enhancement (chelation-enhanced fluorescence = 91 for 2 and 42 for 3) following Hg²⁺ coordination within the limit of detection for Hg²⁺ at 7.5 parts per billion.