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A fluorescein-based chemosensor for “turn-on” detection of Hg2+ and resultant complex as a fluorescent sensor for S2- in semi aqueous medium with cell-Imaging application: Experimental and Computational studies

Abstract

A fluorescein hydrazone based conjugate (H2L3) is synthesized by coupling of fluorescein hydrazide (L1) with 2-(Pyridin-2-ylmethoxy)-napthlene-1-carbaldehyde (L2). H2L3 is well characterized by several spectroscopic methods such as IR, 1H, 13C-NMR and ESI-MS. The probe H2L3 exhibited high selectivity and high sensitivity towards toxic Hg2+ ion in semi aqueous medium (pH 7.2, 10 mM HEPES) over other metal ions. The significant enrichment in fluorescence emission centered at 520 nm was attributed due to Hg2+-induced ring opening of the spirolactam moiety in the fluorescein structure. The 1:1 binding of H2L3 to Hg2+ was established by Job's method and confirmed by ESI-MS+ (m/z) studies and the binding constant was calculated as (0.43 ± 0.04) x 104 M-1 with detection limits of 1.24 µM. Then again, [Hg(HL3)]+ ensemble could be utilized as a reversible fluorescent sensor for S2-. On addition of S2– to the [Hg(HL3)]+ complex, the fluorescence intensity was totally quenched because Hg2+ in the complex was grabbed by S2–because of stronger binding force between Hg2+ and S2–. The tentative coordination environment in the [Hg(HL3)]+ complex was established by DFT studies. The fluorescence “OFF–ON–OFF” mode of H2L3 was examined in the presence of Hg2+ and S2– and finds applications in devices with logic gate functions. The H2L3 also exhibits bio-compatibility and negligible cytotoxicity and is suitable for fluorescence cell imaging of Hg2+ ions in live HepG2 cells.

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Publication details

The article was received on 28 Oct 2018, accepted on 08 Feb 2019 and first published on 09 Feb 2019


Article type: Paper
DOI: 10.1039/C8NJ05418E
Citation: New J. Chem., 2019, Accepted Manuscript

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    A fluorescein-based chemosensor for “turn-on” detection of Hg2+ and resultant complex as a fluorescent sensor for S2- in semi aqueous medium with cell-Imaging application: Experimental and Computational studies

    M. Hasan, A. S. M. Islam, C. Prodhan and M. Ali, New J. Chem., 2019, Accepted Manuscript , DOI: 10.1039/C8NJ05418E

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