Dual‐Mode Calixarene‐Based Chemosensor: Highly Selective Fluorogenic Detection of Hg²⁺ and Chromogenic Detection of Cu²⁺ with a Single Ionophore

Abstract

A fluorescent molecular sensor has been synthesized incorporating a ReI‐bipyridine moiety as a fluorogenic unit and amide‐incorporated modified calix[4]arene as recognition moiety. This molecule behaves as a dual sensor, it exhibited highly selective turn‐on fluorescent sensing for Hg2+ and naked eye colourimetric detection of Cu2+ over a wide range of metal ions. The ion‐competition study revealed no significant interference from any other metal ion used in this study. Mechanistic studies revealed that the combination of soft (nitrogen) and hard (oxygen) donors in the large and flexible macrocyclic coordination site promoted interaction of Hg2+ with nitrogen atoms, which perturbed the fluorescence properties of the molecule restricting the PeT process, and the coordination of Cu2+ with oxygen atoms resulted in new ICT absorption band in the visible region triggering color change. This is a rare example, particularly with calixarene, where a single receptor exhibited dual‐mode selectivity in different sensing channels.

Structural Design, Synthesis, and Preliminary Biological Evaluation of Novel Dihomooxacalix[4]arene-Based Anti-tumor Agents

“…Among those supramolecules, calixarenes are cyclic oligomers composed of phenolic units linked by methylene in the ortho positions, which are considered to be the important class representing the third generation of host-guest supramolecular chemistry. A majority of studies on calixarenes have focused on the fields of molecular recognition due to their flexible nature of the basic moiety preferable for binding and transporting ions and neutral molecules (Ludwig and Dzung, 2002;Mutihac et al, 2011;Gómez-Machuca et al, 2014;Zadmard and Alavijeh, 2014;Patra et al, 2019). In addition, calixarenes have many other structural characteristics including the easy modification of their basic core and rim via covalent attachment to various chemical scaffolds, the limited toxicity and immune responses (Geraci et al, 2008).…”