A Click Fluorophore Sensor that Can Distinguish CuII and HgII via Selective Anion-Induced Demetallation

• Published in: Chemistry : a European journal 2011-03, Vol.17 (10), p.2850-2858
• Main Authors: Lau, Yu Heng, Price, Jason R., Todd, Matthew H., Rutledge, Peter J.
• Format: Article
• Language: English
• Subjects: Anions; Aqueous solutions; azamacrocycles; Chemistry; chemosensors; click chemistry; Fluorescence; Ions; Jewelry; Nitrogen atoms; Sea water; Sensors; Synthesis (chemistry); Triazoles
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201002477

A cyclam‐based fluorescent sensor featuring a novel triazole pendant arm has been synthesised using click chemistry. The sensor is highly responsive to both CuII and HgII 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 S2O32− causes a complete revival of fluorescence only in the case of HgII, providing a simple and effective method for distinguishing solutions containing CuII, HgII or a mixture of both ions, even in doped seawater samples. X‐ray crystal structures of both the HgII sensor complex and a model CuII 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 1H NMR experiments reveal that the mechanism of anion‐induced fluorescence revival involves either displacement of pendant coordination or complete removal of the HgII from the macrocycle, depending on the anion. Strong reaction: Azamacrocyclic complexes with a pendant triazole ligand are easily assembled by using “click” chemistry. By reversing the azide and alkyne coupling partners, a novel triazole scorpion is formed. This gives a fluorescent sensor that responds strongly to CuII and HgII in neutral aqueous solution.