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 C(30)H(38)O(8)N(8)Fe (2) and C(20)H(24)O(4)N(4)Fe (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 Hg(2+) 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(-1) cm(-1); 3, ε = 822 M(-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 Hg(2+) cations. These chemosensors present immense brightness and fluorescence enhancement (chelation-enhanced fluorescence = 91 for 2 and 42 for 3) following Hg(2+) coordination within the limit of detection for Hg(2+) at 7.5 parts per billion.