Visible-near-infrared and fluorescent copper sensors based on julolidine conjugates: selective detection and fluorescence imaging in living cells

Maity, Debabrata ; Manna, Arun K. ; Karthigeyan, D. ; Kundu, Tapas K. ; Pati, Swapan K. ; Govindaraju, T. (2011) Visible-near-infrared and fluorescent copper sensors based on julolidine conjugates: selective detection and fluorescence imaging in living cells Chemistry - A European Journal, 17 (40). pp. 111152-11161. ISSN 0947-6539

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Official URL: http://onlinelibrary.wiley.com/doi/10.1002/chem.20...

Related URL: http://dx.doi.org/10.1002/chem.201101906

Abstract

We present novel Schiff base ligands julolidine–carbonohydrazone 1 and julolidine–thiocarbonohydrazone 2 for selective detection of Cu2+ in aqueous medium. The planar julolidine-based ligands can sense Cu2+ colorimetrically with characteristic absorbance in the near-infrared (NIR, 700–1000 nm) region. Employing molecular probes 1 and 2 for detection of Cu2+ not only allowed detection by the naked eye, but also detection of varying micromolar concentrations of Cu2+ due to the appearance of distinct coloration. Moreover, Cu2+ selectively quenches the fluorescence of julolidine–thiocarbonohydrazone 2 among all other metal ions, which increases the sensitivity of the probe. Furthermore, quenched fluorescence of the ligand 2 in the presence of Cu2+ was restored by adjusting the complexation ability of the ligand. Hence, by treatment with ethylenediaminetetraacetic acid (EDTA), thus enabling reversibility and dual-check signaling, julolidine–thiocarbonohydrazone (2) can be used as a fluorescent molecular probe for the sensitive detection of Cu2+ in biological systems. The ligands 1 and 2 can be utilized to monitor Cu2+ in aqueous solution over a wide pH range. We have investigated the structural, electronic, and optical properties of the ligands using ab initio density functional theory (DFT) combined with time-dependent density functional theory (TDDFT) calculations. The observed absorption band in the NIR region is attributed to the formation of a charge-transfer complex between Cu2+ and the ligand. The fluorescence-quenching behavior can be accounted for primarily due to the excited-state ligand 2 to metal (Cu2+) charge-transfer (LMCT) processes. Thus, experimentally observed characteristic NIR and fluorescence optical responses of the ligands upon binding to Cu2+ are well supported by the theoretical calculations. Subsequently, we have employed julolidine–thiocarbonohydrazone 2 for reversible fluorescence sensing of intracellular Cu2+ in cultured HEK293T cells.

Item Type:Article
Source:Copyright of this article belongs to John Wiley and Sons.
ID Code:93063
Deposited On:08 Jun 2012 09:03
Last Modified:16 Jul 2012 19:21

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