A Click Fluorophore Sensor that Can Distinguish Cu^II and Hg^II via Selective Anion‐Induced Demetallation

Abstract

A cyclam-based fluorescent sensor featuring a novel triazole pendant arm has been synthesised using click chemistry. The sensor is highly responsive to both Cu(II) and Hg(II) in neutral aqueous solution and displays excellent selectivity in the presence of various competing metal ions in 50-fold excess. The addition of specific anions such as I(-) and S(2)O(3)(2-) causes a complete revival of fluorescence only in the case of Hg(II), providing a simple and effective method for distinguishing solutions containing Cu(II), Hg(II) or a mixture of both ions, even in doped seawater samples. X-ray crystal structures of both the Hg(II) sensor complex and a model Cu(II) complex show that pendant triazole coordination occurs through the central nitrogen atom (N2), providing to the best of our knowledge the first reported examples of this unusual coordination mode in macrocycles. Fluorescence, mass spectrometry and (1)H NMR experiments reveal that the mechanism of anion-induced fluorescence revival involves either displacement of pendant coordination or complete removal of the Hg(II) from the macrocycle, depending on the anion.

Coumarin-Derived Fluorescent Chemosensors

“…Some coumarin-derived fluorescent chemosensors exhibit simultaneous sensitivity toward two or more different metal ions, e.g. Cu(II) and Hg(II) based on FRET mechanism (G. He et al, 2010b) or via selective anioninduced demetallation (Lau et al, 2011), Cu 2+ and Ni 2+ (H. , Ni 2+ and Zn 2+ (Chattopadhyay et al, 2006), Ni 2+ and Co 2+ , Ca 2+ and Mg 2+ (Suresh & Das, 2009), Na + and K + (Ast et al, 2011), Hg 2+ and Ag + (Tsukamoto et al, 2011), Cu 2+ /Ni 2+ /Cd 2+ (Lin et al, 2008), Zn 2+ /Cd 2+ /Pb 2+ (Kulatilleke et al, 2006), or Ni 2+ /Pd 2+ /Ag + (Santos et al, 2009).…”

Highly sensitive and selective Hg2+-chemosensor based on dithia-cyclic fluorescein for optical and visual-eye detections in aqueous buffer solution

“…All of these sensors utilized the ligands which responded and bound to Hg 2+ to serve as the ionophores. These ligands included hydroxyquinolines [17,18], cyclens [19,20], cyclams [21][22][23], dioxocyclams [24], diazatetrathia crown ethers [25], azines [26], and calixarenes [27][28][29].…”

A Selective, Colorimetric and Ratiometric Chemosensor for Hg2+ and Its Application as Test Papers

“…), 10 metal ions (Hg 2+ , Cu 2+ , etc. ), 11,12 anions (CN -, F -, etc.). 13,14 Mercury represents for one of the most toxic heavy metals due to its thiophilic nature to proteins and enzymes.…”