Synthesis and characterization of some new Pb(II), Mn(II) and Ag(I) complexes with a pentaaza macrocyclic ligand containing a piperazine moiety

A pentaaza (N₅) 17-membered macrocyclic ligand (L) has been synthesized and its coordination capability toward perchlorate or nitrate salts of Mn(II), Pb(II) and Ag(I) has been investigated. The complexes were characterized by elemental analysis, IR, FAB mass spectrometry, magnetic studies, conductivity measurements, ¹H and ¹³C NMR spectroscopy. The crystal structure of [PbL](ClO₄)₂ has been determined and it shows the presence of a mononuclear complex, with the Pb(II) ion coordinated to the five N donor atoms of the ligand in a hemidirected structure with the presence of a stereochemically active lone pair of electrons on the Pb(II) ion.     

One-pot synthesis of pyrimidines under solvent-free conditions

N,N,N’,N’-Tetrabromobenzene-1,3-disulfonamide was used as an efficient catalyst for the one-pot synthesis of pyrimidine derivatives in excellent yields from triethoxymethane, ammonium acetate, and various ketone derivatives at 100–110 °C under solvent-free conditions.     

X-ray crystal structure and spectral characterization of pseudo five-coordinate Hg(II) polymeric and four-coordinate binuclear complexes of an ambidentate sulfonium ylide

The reaction of ambidentate sulfonium ylide (Me)₂SCHC(O)C₆H₄-p-OCH₃(Y) with HgX₂ [X = Cl (1), Br (2) and I (3)] in equimolar ratios using methanol as the solvent leads to two types of products. Single-crystal X-ray diffraction analysis reveals (i) a two-dimensional polymer, [{HgCl₂(Y)}₄]_n, in which the mercury(II) atom is five-coordinated and ligand Y displays C-coordination as well as an additional interaction, including O-coordination to different mercury centers and (ii) an asymmetric halide-bridged binuclear structure of the type [HgBr₂(Y)]₂, in which the mercury(II) center is four-coordinate and ligand Y displays C-coordination to the metal. The characterization of these compounds by IR, ¹H- and ¹³C NMR spectroscopy confirms the coordination of the ylide to the metal through the carbon atom. Analytical data indicate a 1:1 stoichiometry between the ylide and the Hg(II) halide in all complexes.     

Synthesis,characterization and crystal structure of some new Mn(II) and Zn(II) macroacyclic Schiff base complexes derived from two new asymmetrical (N5) branched amines and pyridine-2-carbaldehyde or O-vaniline and their antibacterial properties

Two new branched pentadentate amines (N₅), 3,6-bis(2-pyridylmethyl)-5 methyl-3,6-diazaheptane diazahexane-1-amine (1) and 4,7-bis(2-pyridylmethyl)-6-methyl-4,7-diazaheptane-1-amine (2) have been prepared. These have been used for the synthesis for the eight new macroacyclic Schiff base complexes, by template [1 + 1] condensation of pyridine-2-carbaldehyde or O-vaniline and amines (1 and 2) in the presence of Mn(II) and Zn(II) metal ions in methanol. The isolated complexes were characterized by a combination of microanalysis, IR and Mass spectroscopy. The structure of MnL¹(ClO₄)₂ indicates that in the solid state the Mn(II) ion adopts a slightly distorted octahedral geometry. The synthesized compounds have antibacterial activity against the three Gram-positive bacteria: Enterococcus faecalis, Bacillus cereus and Staphylococcus epidermidis and also against the three Gram-negative bacteria: Citrobacter freundii, Enterobacter aerogenes and Salmonella typhi. The structure of the complexes derived from pyridine-2-carbaldehyde and metal–ligand interactions in these complexes were also theoretically studied. It was indicated that the structure of complexes is similar to each other and metal–ligand interactions depend mainly on the nature of metal ion and is similar for this series of ligands.     

Simultaneous determination of ascorbic acid,dopamine, and uric acid using a carbon paste electrode modified with multiwalled carbon nanotubes,ionic liquid,and palladium nanoparticles

We describe the modification of a carbon paste electrode (CPE) with multiwalled carbon nanotubes (MWCNT) and an ionic liquid (IL). Electrochemical studies revealed an optimized composition of 60 % graphite, 20 % paraffin, 10 % MWCNT and 10 % IL. In a next step, the optimized CPE was modified with palladium nanoparticles (Pd-NPs) by applying a double-pulse electrochemical technique. The resulting electrode was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, cyclic voltammetry, and electrochemical impedance spectroscopy. It gives three sharp and well separated oxidation peaks for ascorbic acid (AA), dopamine (DA), and uric acid (UA), with peak separations of 180 and 200 mV for AA-DA and DA-UA, respectively. The sensor enables simultaneous determination of AA, DA and UA with linear responses from 0.6 to 112, 0.1 to 151, and 0.5 to 225 μM, respectively, and with 200, 30 and 150 nM detection limits (at an S/N of 3). The method was successfully applied to the determination of AA, DA, and UA in spiked samples of human serum and urine. Figure

The CPE was modified with multiwalled carbon nanotubes and an ionic liquid. After optimization the electrode was further modified with palladium nanoparticles. The resulting electrode gives three sharp and well separated oxidation peaks for ascorbic acid, dopamine and uric acid     

Spectroscopic,theoretical, and antibacterial approach in the characterization of 5-methyl-5-(3-pyridyl)-2,4-imidazolidenedione ligand and of its platinum and palladium complexes

A series of Pt(IV), Pt(II), and Pd(II) complexes (PtCl₄L₂ (1), PtCl₂L₂ (2), PdCl₂L₂ (3), and Pd₂Cl₄L₂ (4)) with 5-methyl-5-(3-pyridyl)-2,4-imidazolidenedione ligand (L) have been synthesized by the reaction of metal chlorides (K₂[PtCl₆], K₂[PtCl₄], K₂[PdCl₄], and PdCl₂) with L in 1:2 (1-3) and 1:1 (4) molar ratios. The binding manner of L, and the composition and geometry of the metal complexes were examined by elemental analysis, IR, ¹H, and ¹³C NMR spectroscopies. Theoretical calculations invoking geometry optimization of different isomers, performed using density functional theory, suggested that in both gas and solution phases the trans isomers are more stable than the cis ones. The experimental results and calculated molecular parameters, bond distances and angles, revealed slightly distorted octahedral (1) and square-planar (2–4) geometry around the metallic center through the pyridine-type nitrogen (N_py) and chlorine atoms. In 4, the binuclear complex, each palladium atom is coordinated by one nitrogen and three chlorine atoms (one as terminal and two as bridging ligands). Antibacterial activity of L and the corresponding complexes was investigated against six species of microorganisms. Testing was performed by disk diffusion method and minimum inhibitory concentrations (MIC) have been determined. The results showed that the title compounds have the capacity of inhibiting the metabolic growth of bacteria to different extents. In general, the binuclear palladium(II) complex was the most active one.     

Influence of crucible geometry and position on the induction heating process in crystal growth systems

A series of 2D finite element numerical simulations of induction heating process for an oxide Czochralski crystal growth system has been done for different shapes and locations of a metal crucible. Comparison between the computational results shows the importance of crucible shape, geometry and its position with respect to the RF-coil on the electromagnetic field and heat generation distribution in the growth setup.     

Synthesis and characterization of some new Co(II) and Cd(II) macroacyclic Schiff-base complexes containing piperazine moiety

Three Cd(II) or Co(II) macroacyclic Schiff-base complexes [CoL¹Br]ClO₄ (1), [CdL²Cl]ClO₄ (2) and [CdL³(NO₃)]ClO₄ (3) were prepared by template condensation of 2-pyridinecarboxaldehyde and three different amines containing piperazine moiety, N,N′-bis(2-aminoethyl)piperazine, N,N′(2-aminoethyl)(3-aminopropyl)piperazine and N,N′-bis(3-aminopropyl)piperazine, in the presence of Co(II) or Cd(II) metal ions, respectively. All complexes have been studied with IR, FAB mass and microanalysis and for complex (3) by ¹H and ¹³C NMR spectra. One of these complexes, [CdL³(NO₃)]ClO₄ (3) has been characterized through X-ray crystallography. In complex (3), the Cd(II) ion is coordinated by the six nitrogen donor atoms from the ligand and by one oxygen atom from a monodentate nitrate ion in a N₆O environment.     

Synthesis and characterization of two zinc(II) macrocyclic Schiff-base complexes containing piperazine moiety, crystal structure of one complex

Two symmetrical and asymmetrical Zn(II) complexes of a pentadentate (N₅) macrocyclic Schiff-base ligands, were prepared via templated [1 + 1] cyclocondensation of 2,6-diacetylpyridine with two different amines containing piperazine moiety. The complexes have been characterized by a variety of methods including, IR, FAB mass spectrometry, elemental analysis and conductivity measurements. The crystal structure of the asymmetric complex, [ZnL¹Br]ClO₄ was determined by X-ray diffraction. It is shown that in the solid state the complex adopts a distorted pentagonal–pyramidal geometry, with the macrocycle in the pentagonal plane and the bromide ion in the axial position.     

First evidence for the use of polyamines as nucleophiles in a regioselective palladium-catalyzed allylic amination reaction

Palladium-catalyzed reaction of unsymmetrical allylic electrophiles with polyamines gives rise to regioisomeric allylic polyamines. An original catalytic procedure providing an efficient method for the regioselective synthesis of new classes of polyamino derivatives of biological interest is reported. Based on experimental considerations, a mechanistic rationale involving a thermodynamically controlled isomerization of the initially formed branched product is proposed to account for the total regioselectivity observed.