New water soluble Hg2 + selective fluorescent calix[4]arenes: Synthesis and application in living cells imaging

• A novel 
•  water soluble fluorescent calix[4]arenes (6 and 7) were designed and synthesized.
• Compounds 6 and 7 are found efficient host for Hg2 + and fluorescein.
• They showed highly selective and sensitive recognition toward Hg2 + based on PET mechanism.
• The utilization of 7 as bio-imaging fluorescent probe was also realized in living cells.

The present study demonstrates the synthesis of water-soluble fluorescent calix[4]arenes (6 and 7) and its application in living cell imaging for Hg2 + detection at a low level. The synthesized fluorescent ligands 6 and 7 were characterized by 1H NMR technique. The fluorescent study showed both water soluble ligands were Hg2 + selective and follow photo-induced electron transfer (PET) process. From the fluorimeter titration experiment detection limit was calculated as 1.14 × 10− 5 and 3.42 × 10− 5 for ligand 6 and 7, respectively. From the Benesi-Hildebrand plot binding constant values were evaluated as 666.7 and 733.3 M− 1 for 6 and 7, respectively. The interactions between ligands 6 and 7 and Hg2 + were also demonstrated in living cells, SW-620, using Fluorescent Cell Imager. While ligands 6 and 7 alone show fluorescent properties, they loss their action with the presence of Hg2 + in SW-620 cells.

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