Calix[4]arenes bearing triazolyl anthracenes: Hg2+-selective receptors exhibiting fluorescence or dual optical responses

Abstract

Calix[4]arenes 1 and 2 bearing two diametrical triazolyl anthracenes on the lower rim have been synthesized as a dual optical sensor and a fluorogenic cation sensor, respectively. UV/vis spectroscopy and fluorescence spectroscopy analyses revealed that receptors 1 and 2 are able to recognize divalent cations such as Ca²⁺, Zn²⁺, Ba²⁺, Hg²⁺, and Pb²⁺ with a significantly higher preference for Hg²⁺, giving rise to different color and fluorescence changes. It was also confirmed by ¹H NMR spectroscopy and fluorescence spectroscopy analyses carried out in acetonitrile that receptor 1 binds the cations via different binding modes resulting in distinct colorimetric and fluorometric responses.