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 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.

Synthesis, Crystal Structure, Electronic Spectroscopy, Electrochemistry and Biological Studies of Ferrocene–Carbohydrate Conjugates

“…All the compounds exhibit two absorption maxima, which are characteristic of the substituted ferrocene compounds. [57] One of the important prerequisites, for the study of biological activity, is the stability of these compounds in aqueous and buffer systems under physiological conditions (pH range 6.0-7.4). [56] The ferrocene-triazoles also exhibit two absorption maxima in the region of 275 nm and around 446 nm ( Figure 2).…”

Fluorescent and colorimetric sensors for environmental mercury detection

“…Proposed sensing mechanism of 109 towards Hg 2+ and structures of 110 and 111 [124][125][126]. Ghosh et al developed the ferrocene-glycine conjugates 112 and 113 (Figure 53) for selective detection of Hg 2+ in aqueous solution, using triazole as the binding site 127. Hg 2+ induces the absorption band at 312 nm to red shift to 324 nm for sensor 114, and the band at 311 nm of sensor 113 red shifts to 321 nm.…”

Synthetic Methodology for Asymmetric Ferrocene Derived Bio-conjugate Systems via Solid Phase Resin-based Methodology

“…[30][31][32][33][34][35][36][37][38] Ferrocene is an organometallic molecule that is a gold standard for electrochemistry, which makes it an excellent choice for integration into electrochemical biosensors. Ferrocene-based redox active species have already garnered considerable attention due to their small size, good stability, convenient synthetic access, easy chemical modification, relative lipophilicity, and ease of redox tuning.…”

“…3,[30][31][32][33][34][35][36][37][38][39][40][41][42] Small molecules based on the ferrocene core have been used extensively as detectors of metal ions and small molecules. [32][33][34][35][36][37][38]43 Systems targeting larger species such as biomolecules have utilized the attachment of large antibodies or immunoglobulins to ferrocene derivatives that have been embedded onto an electrochemical surface. 1,3,39,44 In each case, the potential and current intensity of the Fe III /Fe II redox couple was altered upon molecular coupling, thus producing a new spectroscopic handle indicating the presence of the analyte molecule.…”