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Nickel is considered as an important toxic pollutant and is continuously released into the biosphere by some anthropogenic activities such as industrial and urban sewage. The main objective of this study was to determine the concentration of nickel in different samples of soil, water, and muscle tissue of fish species which were collected from the Persian Gulf. For this propose, a simple and sensitive solid-phase extraction using pyridine-functionalized Mobil Composition of Matter (MCM)-41 and MCM-48 nanoporous silica was developed and their application in preconcentration and determination of nickel by flame atomic absorption spectrometry was studied. Limit of detection was found to be lower than 3.5 μg L. Recovery and precision of the method were above 98.5% and below 1.5%, respectively. To gauge their ability in terms of application to natural samples, the proposed method was applied to a number of natural samples including plants, water, soil and fish species, and the amount of nickel was determined by spiking known concentrations of nickel into the solution. The results show that pollution of soil and water has some effects on bioaccumulation of Ni on marine organisms and plants that could magnify along the food chain. [ABSTRACT FROM AUTHOR]

Employing DFT and handling the solvent effects with the PCM model, the 1-acetylpiperazinyldithiocarbamate acpdtc ligand and its M(acpdtc) complexes, where M is Mn(II), Fe(II), Co(II), Ni(II) and Cu(II), are characterized computationally. The obtained results suggest that the piperazine ring adopts chair conformation in all the studied species. In the gas and solution phases, the chair form of the ligand is dominant. For the Mn, Fe and Co complexes the tetrahedral structure is more stable than the square form in the gas and solution phases. However, the Ni and Cu complexes adopt the square form, in which the complex has the inversion center. The calculated vibrational frequencies are in agreement with the experimental ones, confirming the suitability of the optimized geometries of the compounds. Atomic charges, electron distribution of the frontier orbitals, and stabilizing electron transfers are determined by the NBO analysis. [ABSTRACT FROM AUTHOR]

A new tetradentate N,N′-dipyridoxyl(1,2-ethylenediamine) [=HES] Schiff-base ligand and its Cu(II) salen complex [Cu(ES)(HO)] are synthesized and characterized by IR, UV-Vis, H NMR, mass spectrometry, and elemental analysis. Their optimized geometries and theoretical vibrational frequencies are computed by using the density functional theory method where the B3LYP functional was used. Also, the H NMR chemical shifts of the HES ligand are calculated at the same computational level. In the optimized structure of the free ligand, two pyridine rings are not in the same plane. In the structure of the complex, the Schiff-base ligand acts as a dianionic tetradentate ligand in the N, N, O, O manner, so that the coordinating atoms occupy equatorial positions. The HO ligand occupies the axial position of the squarepyramidal complex. The calculated results are consistent with the experimental ones, confirming the suitability of the optimized structures for the HES ligand and its Cu(II) complex. [ABSTRACT FROM AUTHOR]