Synthesis and characterisation of calix[4]arene based bis(triazole)-bis(hexahydroquinoline): Probing highly selective fluorescence quenching towards mercury (Hg 2+ ) analyte.

In the present study, we are reporting the synthesis of a triazoles incorporated fluorescent hexahydroquinoline appended calix[4]arene 7 and its highly selective optical recognition ability towards Hg ²⁺ . The optical sensor 7 was synthesized via two different synthetic pathways and unambiguously characterized by mass spectrometry and NMR spectroscopy. The stoichiometric ratio between 7 and Hg ²⁺ was determined as 1:1 based on Job's plot and ESI-MS analysis. The chemosensor 7 selectively recognized Hg ²⁺ in the presence of competitive cations such as Cu ²⁺ , Cu ¹⁺ , Co ³⁺ , Ni ²⁺ , Ag ¹⁺ , Fe ²⁺ , Fe ³⁺ , Cr ³⁺ , Pb ²⁺ , Cd ²⁺ , Zn ²⁺ , Sn ²⁺ , Ti ⁴⁺ , Sb ³⁺ , In ³⁺ , Ba ²⁺ , Ca ²⁺ , and K ¹⁺ . The limit of detection (LOD) was established as 0.5 μM on spectrofluorimetric analysis. According to world health organization (WHO) in guidelines for drinking-water quality, the mercury level in natural occurring ground and surface water is about ∼0.5 μM (μg/L). The supra molecule 7 with LOD (0.5 μM) could potentially serve effective receptors for Hg ²⁺ cation. The probe 7 was applied effectively for detection of Hg ²⁺ in real water samples (i.e. tap and deionized water), spiked with Hg ²⁺ (10 μM) solution. Moreover, the compound 7 showed non-toxicity during cytotoxic assay against human B cells as they retain their morphology. The supramolecule 7 in living cells showed selectivity towards Hg ²⁺ in cytotoxic assay with T lymphocytes, evident by morphological changes observed via AFM analysis.
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