Selective and sensitive turn on fluorescence cyanide recognition in aqueous medium based on Zn(II)-hydrazone metal complex chemosensor.

Detection and quantification of the cyanide ion (CN- ) has attracted considerable attention because of its extreme toxicity. A novel Zn(II)-complex, applicable as a fluorescent chemosensor for CN- recognition, was synthesized in excellent yields from the reaction of zinc sulfate with the novel hydrazone: 3-(amino-9H-purin-yl)-N'-(hydroxybenzylidene) propanehydrazide. The structures of the hydrazone (L) and the zinc-hydrazone complex (L.Zn) were characterized by ultraviolet-visible spectrophotometry, Fourier-transform infrared spectrometry, mass spectrometry, proton- and carbon-13-nuclear magnetic resonance. The sensing performance of the proposed chemosensors, L and L.Zn, towards common ions was investigated via naked-eye studies as well as absorption and emission spectral analysis. Hydrazone (L) efficiently functioned as a fluorescence sensor for aluminum ions (Al3+ ) and zinc ions (Zn2+ ) with large binding constants, and exhibited colorimetric and fluorometric responses for several basic anions: OH- , CO3 2- , HCO3 - , HSO3 - , CH3 COO- and CN- . However, L.Zn showed quick, sensitive and specific enhancement of fluorescence intensity towards CN- anion, and a linear relationship was observed as the concentration of CN- varied from 1 to 14 µM. The detection limit was determined to be 0.14 µM, which is lower than the 1.9 µM maximum value recommended by the World Health Organization for drinking water. The practical performance of the sensor was successfully demonstrated using various environmental water samples spiked with cyanide ion.

Interactions of Some Divalent Metal Ions with Thymine and Uracil Thiosemicarbazide Derivatives.

The study of interactions between metal ions and nucleobases, nucleosides, nucleotides, or nucleic acids has become an active research area in chemical, biological, and therapeutic fields. In this respect, the coordination behavior of nucleobase derivatives to transition metals was studied in order to get a better understanding about DNA-metal interactions in in vitro and in vivo systems. Two nucleobase derivatives, 3-benzoyl-1-[3-(thymine-1-yl)propamido]thiourea and 3-benzoyl-1-[3-(uracil-1-yl)propamido]thiourea, were synthesized and their dissociation constants were determined at different temperatures and 0.3 ionic strength. Potentiometric studies were carried out on the interaction of the derivatives towards some divalent metals in 50% v/v ethanol-water containing 0.3 mol.dm(-3) KCl, at five different temperatures. The formation constants of the metal complexes for both ligands follow the order: Cu(2+) > Ni(2+) > Co(2+) > Zn(2+) > Pb(2+) > Cd(2+) > Mn(2+). The thermodynamic parameters were estimated; the complexation process has been found to be spontaneous, exothermic, and entropically favorable.

Thiophene aldehyde-diamino uracil Schiff base: A novel fluorescent probe for detection and quantification of cupric, silver and ferric ions.

A new Schiff base from the condensation of 5,6-diamino-1,3-dimethyluracil with 5-methylthiophene-2-carboxaldehyde was synthesized. The compound was characterized by spectral data (UV-Vis, IR, (1)H NMR, fluorescence, MS). Ethanolic solutions of the Schiff base exhibit a strong fluorescence emission at 385 nm (λex=341 nm), and have been employed as a "turn-off" fluorescent probe for selective detection of Ag(+), Cu(2+) and Fe(3+) ions in presence of other cations such as Na(+), K(+), Ca(2+) and Mg(2+) ions abundant in natural water. The interaction between the tested compound and copper, silver or iron ions is associated with a significant fluorescence decrease, showing detection limits of 2.1-14.2 ppb. Under optimal conditions, the developed sensor was successfully employed to determine Ag(+), Cu(2+) and Fe(3+) ions in real samples and proved to be selective and sensitive.