A Highly Selective Redox, Chromogenic, and Fluorescent Chemosensor for Hg2+ in Aqueous Solution Based on Ferrocene-Glycine Bioconjugates

The synthesis, electrochemical, optical, and metal-cation-sensing properties of ferrocene glycine conjugates C30H38O8-N8Fe (2) and C20H24O4N4Fe (3) have been documented. Both compounds 2 and 3 behave as very selective redox (Delta E-1/2 = 217 mV for 2 and Delta E-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, epsilon = 1600M(-1) cm(-1) ; 3, epsilon = 822M(-1) cm(-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.