A naphthalene-thiophene hybrid molecule as a fluorescent AND logic gate with Zn2+ and OAc- ions as inputs: cell imaging and computational studies.

A naphthalene-thiophene hybrid molecule (Z)-1-((thiophen-2-ylmethylamino)methylene)naphthalen-2(1H)-one () was prepared by condensation of 2-thiophenemethylamine and 2-hydroxy-1-naphthaldehyde. According to FTIR, (1)H NMR spectrometry and single crystal X-ray analysis, exists in the cis-keto-amine tautomeric form. behaves like a molecular AND type binary logic gate with two inputs viz. Zn(2+) and OAc(-) ions whereby the fluorescence of the system turns on. The structures of and its zinc acetate complex were also optimized by DFT calculations. binds Zn(2+) in a 1 : 1 ratio with an association constant K(a) = 2.05 × 10(4) M(-1), and detects Zn(2+) as low as 3 × 10(-8) M. is useful for the detection of intracellular Zn(2+) under a fluorescence microscope.

A naphthalene-based Al3+ selective fluorescent sensor for living cell imaging.

An efficient fluorescent Al(3+) receptor, N-(2-hydroxy-1-naphthalene)-N'-(2-(2-hydroxy-1-naphthalene)amino-ethyl)-ethane-1,2-diamine (L) has been synthesized by the condensation reaction between 2-hydroxy naphthaldehyde and diethylenetriamine. High selectivity and affinity of L towards Al(3+) in ethanol (EtOH) as well as in HEPES buffer at pH 7.4, makes it suitable to detect intracellular Al(3+) with fluorescence microscopy. Metal ions, viz. Li(+), Na(+), K(+), Mg(2+), Ca(2+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Ag(+), Cd(2+), Hg(2+) and Pb(2+) do not interfere. The lowest detection limit for Al(3+) is 3.0 × 10(-7) M and 1.0 × 10(-7) M in EtOH and HEPES buffer respectively.

9-Acridone-4-carboxylic acid as an efficient Cr(III) fluorescent sensor: trace level detection, estimation and speciation studies.

9-Acridone-4-carboxylic acid has been established as an efficient Cr(III) fluorescent sensor. The binding of this ligand with Cr(III) is confirmed by FTIR, thermal and mass spectral analysis of the product. Based on this chelation assisted fluorescence quenching, a highly sensitive spectrofluorometric method is developed for trace level detection, estimation and speciation studies of chromium in DMF-water. The ligand has an excitation and emission maxima at 408 nm and 498.4 nm, respectively. The equilibrium binding constant of the ligand with Cr(III) is 8.1378 × 10(4) as calculated using Stern-Volmer equation. Up to 9 × 10(-6)mol L(-1) of [Cr(3+)], linearity has been observed. The interference of foreign ions has been found to be negligible.

Methionine-pyrene hybrid based fluorescent probe for trace level detection and estimation of Hg(II) in aqueous environmental samples: experimental and computational studies.

A new fluorescent, Hg(2+) selective chemosensor, 4-methylsulfanyl-2-[(pyren-4-ylmethylene)-amino] butyric acid methyl ester (L, MP) was synthesized by blending methionine with pyrene. It was well characterized by different analytical techniques, viz. (1)H NMR, (13)C NMR, QTOF mass spectra, elemental analysis, FTIR and UV-vis spectroscopy. The reaction of this ligand with Hg(2+) was studied by steady state and time-resolved fluorescence spectroscopy. The Hg(2+) complexation process was confirmed by comparing FTIR, UV-vis, thermal, QTOF mass spectra and (1)H NMR data of the product with that of the free ligand values. The composition (Hg(2+):L=1:1) of the Hg(2+) complex in solution was evaluated by fluorescence titration method. Based on the chelation assisted fluorescence quenching, a highly sensitive spectrofluorometric method was developed for the determination of trace amounts of Hg(2+) in water. The ligand had an excitation and emission maxima at 360 nm and 455 nm, respectively. The fluorescence life times of the ligand and its Hg(2+) complex were 1.54 ns and 0.72 ns respectively. The binding constant of the ligand, L with Hg(2+) was calculated using Benesi-Hildebrand equation and was found to be 7.5630×10(4). The linear range of the method was from 0 to 16 µg L(-1) with a detection limit of 0.056 µg L(-1) for Hg(2+). The quantum yields of the ligand and its Hg(2+) complex were found to be 0.1206 and 0.0757 respectively. Both the ligand and its Hg(2+) complex have been studied computationally (Ab-initio, Hartree Fock method) to get their optimized structure and other related physical parameters, including bond lengths, bond angles, dipole moments, orbital interactions etc. The binding sites of the ligand to the Hg(2+) ion as obtained from the theoretical calculations were well supported by (1)H NMR titration. The interference of foreign ions was negligible. This method has been successfully applied to the determination of mercury(II) in industrial waste water.

Pyridine appended L-methionine: a novel chelating resin for pH dependent Cr speciation with scanning electron microscopic evidence and monitoring of yeast mediated green bio-reduction of Cr(VI) to Cr(III) in environmental samples.

Chemical speciation and pH dependent separation of Cr(III) and Cr(VI) species in environmental samples have been achieved by solid phase extraction using a new chelating resin containing pyridine appended L-methionine. Cr(III) is completely sorbed on the resin at pH 8.0 and Cr(VI) at pH 2.0. Hence a pH dependent separation of Cr(III) and Cr(VI) is possible with a limit of detection of 1.6 µg mL(-1) and 0.6 µg mL(-1) respectively. The sorption capacity of the resin for Cr(III) and Cr(VI) is 2.8 mmol g(-1) and 1.3 mmol g(-1) respectively. The sorption of chromium on the resin is supported by scanning electron microscopy (SEM). Complete desorption of Cr(III) and Cr(VI) from 1g of Cr loaded resin was achieved using 10 mL of 2 mol L(-1) HNO(3) and 6 mL of 3 mol L(-1) HNO(3) respectively. Quantitative recoveries of Cr(III) (pH 8.0) and Cr(VI) (pH 2.0) were found to be 96.0% and 98.0% respectively. Reduction efficiency of Rhodotornula mucilaginosa yeast from Cr(VI) to Cr(III) was monitored with this new resin. Concentrations of metal ions were measured by flame atomic absorption spectroscopy (FAAS).