RESUMEN
This research involved constructing and studying plastic membrane Cd(ii)- and Pb(ii)-ion selective electrodes of the coated wire type based on nanoparticles of CdS and PbS as ionophores, respectively. The electrodes exhibited average linear concentration ranges of 1.0 × 10-6 to 1.0 × 10-2 and 9.6 × 10-7 to 1.0 × 10-2 M, average detection limits of 8.6 × 10-7 and 5.8 × 10-7 M, pH ranges of 2.2-5.8 and 2.9-5.9, and average calibration graph slopes of 28.56 and 28.81 mV per concentration decade, respectively. Both electrodes showed high selectivity towards many inorganic cations. Depth profiling X-ray photoelectron spectroscopy of fresh and expired membranes proved that: (a) the nanoparticles were homogeneously dissolved in the polymeric network and (b) the limitation of the life span of the plastic membrane was due to leaching of the active ingredient from the membrane surface to the bathing solution. The topography of fresh, active, and expired membranes as imaged by atomic force microscopy revealed the formation of a gel layer at the surface of the active electrode and drastic deformation of the expired membrane's surface.
RESUMEN
A new series of Zn(2+), Cu(2+), Ni(2+), and Co(2+) complexes of N(1)-methyl-2-(1H-1,2,3-benzotriazol-1-yl)-3-oxobutanethioamide (MBOBT), HL, has been synthesized and characterized by different spectral and magnetic measurements and elemental analysis. IR spectral data indicates that (MBOBT) exists only in the thione form in the solid state while 13C NMR spectrum indicates its existence in thione and thiole tautomeric forms. The IR spectra of all complexes indicate that (MBOBT) acts as a monobasic bidentate ligand coordinating to the metal(II) ions via the keto-oxygen and thiolato-sulphur atoms. The electronic spectral studies showed that (MBOBT) bonded to all metal ions through sulphur and nitrogen atoms based on the positions and intensity of their charge transfer bands. Furthermore, the spectra reflect four coordinate tetrahedral zinc(II), tetragonally distorted copper(II), square planar nickel(II), and cobalt(II) complexes. Thermal decomposition study of the complexes was monitored by TG and DTG analyses under N(2) atmosphere. The decomposition course and steps were analyzed and the activation parameters of the nonisothermal decomposition are determined. The isolated metal chelates have been screened for their antimicrobial activities and the findings have been reported and discussed in relation to their structures.
RESUMEN
The reaction of NiCl(2).H(2)O with 1-benzotriazol-1-yl-[(p-X-phenyl)hydrazone]propan-2-one, X=H (HL(1)), X=Cl (HL(2)), X=Br (HL(3)) and X=Me (HL(4)), gave the complexes [(HL)NiCl(2)] x nH(2)O and [LNi(OH)](2), where L is the monobasic anion of HL(2) or HL(3). The nature of the products is solvent and ligand dependent. The complexes are characterized by elemental analyses, molar conductivity, magnetic moments and spectroscopic (IR and UV/vis) measurements. The IR showed that the ligands act as neutral bidentate coordinated to the nickel(II) through the azomethine nitrogen and carbonyl oxygen atoms in case of [(HL)NiCl(2)] x nH(2)O. In case of [LNi(OH)](2), the ligands are monobasic bidentate bonded to the nickel(II) through the azomethine nitrogen and the enolato oxygen atoms. The room temperature magnetic moment values of 1.58-2.49 B.M. for [(HL)NiCl(2)] x nH(2)O and [LNi(OH)](2) and their electronic spectral data indicate that these complexes have square planar-tetrahedral equilibrium. The values of 1.61 and 1.58 B.M. for the hydroxo-complexes support their dimeric nature. The electronic spectral of [(HL)NiCl(2)] x nH(2)O and [LNi(OH)](2) in pyridine or alpha-picoline indicated the formation of six-coordinate adducts. The hydroxo-complexes reacted with different Lewis bases to give the complexes [L(2)Ni(L(s))(2)], where L(s)=Py, 2-Pic, 3-Pic, 4-Pic or n-PrNH(2). The relationship between the pK(b) of the Lewis base and the upsilon(Ni-O) of the ligand and upsilon(Ni-N) of the Lewis base was studied. The different ligand field parameters are calculated for the parent ligands in solutions and the solid mixed ligand complexes. The data showed that both are associated with a distorted octahedral ligand field around the nickel(II) and the ligand fields in solution are different from that in solid. The extent of distortion for the parent complexes is more than that in the solid adducts. Furthermore, the data showed that the nickel-ligand bonding in [LNi(OH)](2) is more covalent than in [L(2)Ni(L(s))(2)].