Synthesis and characterisation of calix[4]arene based bis(triazole)-bis(hexahydroquinoline): Probing highly selective fluorescence quenching towards mercury (Hg2+) analyte

Abstract

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 Hg2+. 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 Hg2+ was determined as 1:1 based on Job’s plot and ESI-MS analysis. The chemosensor 7 selectively recognized Hg2+ in the presence of competitive cations such as Cu2+, Cu1+, Co3+, Ni2+, Ag1+, Fe2+, Fe3+, Cr3+, Pb2+, Cd2+, Zn2+, Sn2+, Ti4+, Sb3+, In3+, Ba2+, Ca2+, and K1+. 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 Hg2+ cation. The probe 7 was applied effectively for detection of Hg2+ in real water samples (i.e. tap and deionized water), spiked with Hg2+ (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 Hg2+ in cytotoxic assay with T lymphocytes, evident by morphological changes observed via AFM analysis.