Anthracene-Based Highly Selective and Sensitive Fluorescent "Turn-on" Chemodosimeter for Hg2.

Three π-extended anthracene-bearing thioacetals (1-3) have been synthesized, and their fluorescence "turn-on" responses to Hg2+ ions are studied. The chemodosimetric fluorescence-sensing behavior and their resulting hydrolysis via a desulfurization reaction mechanism leads to the formation of highly fluorescent respective aldehyde substitutions. Furthermore, this mechanism was supported by increase in the quantum yields of their resulting aldehydes and is correlated to their molecular substitution. The chemosensors 1-3 have exhibited to be promising receptors toward Hg2+ ions in the presence of other competitive metal ions. Moreover, the detection limits of 1-3 have been found to be in the nanomolar range (94, 59, and 235, respectively). Fluorescence microscopic imaging studies show that 1-2 have been found to be effective for fluorescence imaging in live cells. Moreover, compounds 1-3 act as potential candidates for the detection of Hg2+ in environmental and biological systems as well as real samples.

A new multifunctional benzimidazole tagged coumarin as ratiometric fluorophore for the detection of Cd2+/F- ions and imaging in live cells.

A novel multifunctional ratiometric fluorescent probe has been designed and synthesized for the selective recognition of Cd2+/F- ions. The probe (3)-((2)-(1H-benzoimidazole-2-yl)-phenylimino) methyl-4-chloro-methyl-2H-chromen-2-ene (BIMC) displays excellent ratiometric responses towards Cd2+/F- ions over the tested cations/anions. The lowest detection limits observed for Cd2+ and F- are 1.5 × 10-10 mol/l and 1.2 × 10-10 mol/l respectively. Job's plot and Electro spray Ionization mass spectral (ESI-MS) studies confirms 1:1 binding stoichiometry of BIMC with Cd2+/F- ions, which is further evidenced by 1H NMR titration studies. The reversibility studies of BIMC with Cd2+ have been investigated using ethylenediaminetetraacetic acid (EDTA). Upon binding to Cd2+/F- ions, the probe features strong ratiometric response in both UV-Visible and fluorescence spectra due to the inhibition of intramolecular charge transfer (ICT). Furthermore, the mechanism of ICT has been rationalized via solvatochromism and DFT calculations.

Charge transfer based "turn-on" chemosensor for Zn²âº ion recognition using new triaryl pyrazoline derivative.

The fluoroionophore PY serves as a selective and fluorimetric chemosensor for Zn(2+) based on charge transfer (CT). A mechanism for the binding mode was proposed based on fluorescence changes, NMR experiments and theoretical calculations. The 1:1 stoichiometry between Zn(2+) and the sensor was deduced from Job's plot. The addition of EDTA quenches the fluorescence of PY.Zn(2+) complex offers PY as a reversible chemosensor.

Aminobenzohydrazide based colorimetric and 'turn-on' fluorescence chemosensor for selective recognition of fluoride.

Chemosensors based on aminobenzohydrazide Schiff bases bearing pyrene/anthracene as fluorophores have been designed and synthesized for F(-) ion recognition. The addition of fluoride ions to the receptors causes a dramatically observable colour change from pale yellow to brown/red. (1)H NMR studies confirm that the F(-) ion facilitates its recognition by forming hydrogen bond with hydrogens of amide and amine groups. Moreover these sensors have also been successfully applied to detection of fluoride ion in commercial tooth paste solution.

Aminoquinoline based highly sensitive fluorescent sensor for lead(II) and aluminum(III) and its application in live cell imaging.

We have synthesized a new probe 5-((anthracen-9-ylmethylene) amino)quinolin-10-ol (ANQ) based on anthracene platform. The probe was tested for its sensing behavior toward heavy metal ions Hg(2+), Pb(2+), light metal Al(3+) ion, alkali, alkaline earth, and transition metal ions by UV-visible and fluorescent techniques in ACN/H2O mixture buffered with HEPES (pH 7.4). It shows high selectivity toward sensing Pb(2+)/Al(3+) metal ions. Importantly, 10-fold and 5- fold fluorescence enhancement at 429 nm was observed for probe upon complexation with Pb(2+) and Al(3+) ions, respectively. This fluorescence enhancement is attributable to the prevention of photoinduced electron transfer. The photonic studies indicate that the probe can be adopted as a sensitive fluorescent chemosensor for Pb(2+) and Al(3+) ions.

Novel indole based dual responsive "turn-on" chemosensor for fluoride ion detection.

An efficient new dual channel chemosensor 2,3-bis((E)-(1H-indole-3-yl)methyleneamino)maleonitrile (DN) which exhibits selective sensing of F(-) ions in DMSO, was synthesized by a facile one step condensation reaction of indole-3-carboxaldehyde with diaminomaleonitrile. The probe DN was characterized by elemental analysis, (1)H, (13)C-NMR, ESI-MS and IR spectral techniques. Upon addition of F(-), DN induces remarkable changes in both absorption and fluorescence spectra on the basis of charge transfer mechanism. The receptor DN serves for highly selective, sensitive detection of F(-) without the interference of other relevant anions. The Job's plot analysis indicates the binding stoichiometry to be 1:1 (host/guest).

Hg(2+) mediated quinazoline ensemble for highly selective recognition of Cysteine.

A fluorimetric sensor for Hg(2+) ion and Cysteine based on quinazoline platform was designed and synthesized by one step reaction and characterized by using common spectroscopic methods. Time Dependent Density Functional Theory calculations shows that probe behaves as "ON-OFF" fluorescent quenching sensor via electron transfer/heavy atom effect. Receptor was found to exhibit selective fluorescence quenching behavior over the other competitive metal ions, and also the receptor-Hg(2+) ensemble act as an efficient "OFF-ON" sensor for Cysteine. Moreover this sensor has also been successfully applied to detection of Hg(2+) in natural water samples with good recovery.

Triazole based ratiometric fluorescent probe for Zn2+ and its application in bioimaging.

An efficient fluorescent chemosensor 4-((2-hydroxynaphthalen-1-yl)methyleneamino)-3-phenyl-1H-1,2,4-triazole-5(4H)-thione, based on triazole has been designed by condensing 2-hydroxy-1-napthaldehyde with amine, appended to 1,2,4-triazole unit. The probe displays excellent selectivity and sensitivity in both absorbance and fluorescence detection of Zn2+ over other essential metal ions. The nature of fluorescence behavior of receptor upon addition of Zn2+ has been obtained from Density Functional Theory calculations. Imaging experiment indicates that probe works effectively for intracellular Zn2+ imaging with good cell permeability and biocompatibility.

Rhodamine based sensor for naked-eye detection and live cell imaging of fluoride ions.

A rhodamine based highly selective colorimetric and fluorescent probe for fluoride has been designed and synthesized. The fluorescent change is attributed to the fluoride triggered spirolactam ring opening which is augmented by density functional theory calculations and 1H NMR titrations. The sensor has been shown to be feasible for real sample analysis, and imaging of fluoride ions in the HeLa cells.

Turn-on fluorescent chemosensor for Zn(II) via ring opening of rhodamine spirolactam and their live cell imaging.

A new rhodamine based selective and sensitive turn-on fluorescent Zn(2+)chemosensor has been developed. A prominent fluorescence enhancement was found in the presence of Zn(2+), which was accompanied by changes in the absorption spectrum. The new sensor showed 'naked-eye' detection of Zn(2+) ions: a color change of the solution from colorless to pink. Furthermore, by means of confocal laser scanning microscopy experiments, it has been demonstrated that it can be used as a fluorescent probe for monitoring Zn(2+) in living cells.