Amina A. Soayed

Studies on Some Schiff Base Complexes of CoII, NiII and CuII Derived from Salicylaldehyde and O-Nitrobenzaldehyde

Abstract Schiff bases of the type salicylidene 2-aminobenzothiazole and o-nitrobenzylidene 2-aminobenzothiazole were prepared by condensation of 2-aminobenzothiazole with salicylaldehyde and o-nitrobenzaldehyde. The bases react with cobalt(II), nickel(II) and copper(II) chlorides to give 1:1 and 1:2 complexes. Electronic spectra, magnetic susceptibility measurements and infrared data are used to infer the structures. The thermal decomposition of the complexes and evaluation of the thermodynamic parameters are also reported.

SYNTHESIS AND CHARACTERIZATION OF NEW AZOPYRIMIDINE COMPLEXES

New azo compounds containing barbituric acid, thiobarbituric acid or thiouracil, together with their complexes, were prepared. All the complexes are tetrahedral. Axial ESR spectra were observed for the complexes with a dx2� y2 ground state with small g|| values indicating strong interaction between the ligands and their metal ions. Conductivity measurements proved semiconducting properties for the ligands and their complexes. Energies of activation (Ea) and order of the thermal reactions (n) were calculated by DTA.

Structural chemistry of azo complexes

SummaryComplexes of CoII, NiII, CuII, PdII, and PtIV with 2,4,5-trihydroxybenzoic acid and its substituted phenylazoderivatives have been prepared, together with some mixed-metal (Co, Cu or Ni, Cu) complexes of itsm-nitro,m-carboxy andm-hydroxyarylazo derivatives. The stereochemistries and the modes of bonding of the complexes were elucidated by spectral and magnetic susceptibility measurements.

Coordination modes, spectral, thermal and biological evaluation of hetero-metal copper containing 2-thiouracil complexes.

Mononuclear copper complex [CuL(NH(3))(4)]Cl(2)·0.5H(2)O and three new hetero-metallic complexes: [Cu(2)Ni(L)(2)(NH(3))(2)Cl(2)·6H(2)O] 2H(2)O(,) [Cu(3)Co(L)(4)·8H2O]Cl·4(·)5H(2)O, and [Cu(4)Co(2)Ni(L)(3)(OH)(4)(NH(3))Cl(4)·3H(2)O]4H(2)O where L is 2-thiouracil, were prepared and characterized by elemental analyses, molar conductance, room-temperature magnetic susceptibility, spectral (IR, UV-Vis and ESR) studies and thermal analyses techniques (TG, DTG and DTA). The molar conductance data revealed that [CuL(NH(3))(4)]Cl(2)·0.5H(2)O and [Cu(3)Co(L)(4)·8H2O]Cl·4.5H(2)O are electrolytes, while, [Cu(2)Ni(L)(2)(NH(3))(2)Cl(2·)6H(2)O]·2H(2)O and [Cu(4)Co(2)Ni(L)(3)(OH)(4)(NH(3))Cl(4)·3H(2)O]4H(2)O are non-electrolytes. IR spectra showed, that 2-thiouracil ligand behaves as a bidentate or tetradentate ligand. The geometry around the metal atoms is octahedral in all the prepared complexes except in [Cu(4)Co(2)Ni(L)(3)(OH)(4)(NH(3))Cl(4)·3H(2)O]4H(2)O complex where square planar environment around Co(II), Ni(II) and Cu(II) were suggested. Thermal decomposition study of the prepared complexes was monitored by TG, DTG and DTA analyses under N(2) atmosphere. The decomposition course and steps were analyzed. The order of chemical reactions (n) was calculated via the peak symmetry method and the activation parameters of the non- isothermal decomposition were computed from the thermal decomposition data. The negative values of ΔS(∗) deduced the ordered structures of the prepared complexes compared to their starting reactants. The antimicrobial activity of the prepared complexes were screened in vitro against a Gram positive, a Gram negative bacteria, a filamentous fungi and a yeast. The antimicrobial screening data showed that the studied compounds exhibited a good level of activity against Escherichia coli, Staphylococcus aureus and Candida albicans but have no efficacy against Aspergillus flavus. It was observed that [Cu(4)Co(2)Ni(L)(3)(OH)(4)(NH(3))Cl(4)·3H(2)O]4H(2)O complex showed the most intensive activity against the tested microorganisms. Trials to prepare single crystals from complexes were failed.

Synthesis and spectroscopic studies on (4,5-dimethyl-3-pyrazolyl) aldazine nickel(II) complexes

Summary(4,5-Dimethyl-3-pyrazolyl)aldazine, L, reacts with nickel(II) salts to form 1∶1 and 1∶2 complexes. The 1∶1 binuclear systems involve two ligands bridging two nickels, in which L behaves as a tetradentate ligand, and the nickel(II) complexes have pseudo-octahedral stereo-chemistry. Some of the 1∶1 and 1∶2 complexes contain coordinated H2O and bridging OH. Structures of these complexes are proposed on the basis of elemental analyses, conductivity, spectral data (u.v.-vis. and i.r.) and magnetic susceptibilities.

Solvatochromic responses and pH effects on the electronic spectra of some azo derivatives of 1-amino-2-hydroxy-4-naphthalenesulfonic acid

Synthesis and characterization of five arylazo derivatives of 1-amino-2-hydroxy-4-naphthalenesulfonic acid (H2L1) are reported. The UV/Vis absorption spectra of the parent compound (H2L1) and its arylazo derivatives (H2L2–H4L6) have been measured at room temperature in seven solvents of different polarities and with variable parameters. The electronic transitions were analyzed using SPSS program, linear regression technique and Kamlet–Taft’s equation to permit a good understanding of solvent-induced spectral shifts. The electronic absorption spectra of the prepared compounds containing different substituents were studied in aqueous solutions at different pH values. The pK values of the investigated compounds were evaluated spectrophotometrically. The prevailing acid species present at any pH range are judged from the constructed distribution diagrams.

THE COORDINATION OF Cu(II) AND THERMAL STUDIES ON SOME QUINOXALINONE DERIVATIVE COMPOUNDS

The chelates of Cu(II) ion with some quinoxalinone compounds have been prepared and characterized by elemental analysis, IR, UV-Vis, magnetic susceptibility and TGA. It is shown that the ligands behave as bi- or tridentate ligands with the coordination of one or two chloride atoms in most of the complexes. The thermal decomposition of the compounds has been used to confirm structural information.

The Ni(II) Complex of 2-Hydroxy-Pyridine- N-Oxide 2-Isothionate: Synthesis, Characterization, Biological Studies, and X-ray Crystal Structures using (1) Cu Kα Data and (2) Synchrotron Data

C 12 H 20 N 6 NiO 6 S 2 or NiL 2 (SCN) 2 ](NH 4 ) 2 .2H 2 O, where L is 2-hydroxy-pyridine-N-oxide, has been prepared and characterized using elemental analyses, IR, UV and visible spectrometry, magnetic moment measurements, thermal analyses and single crystal X-ray analyis. The results indicate that the complex reacts as a bidentate ligand and is bound to the metal ion via the two oxygen atoms of the ligand (HL). The activation energies, ∆ E*, entropies ∆S*, enthalpies ∆H* and order of reactions have been derived from differential thermogravimetric (DTA) curves. Based on inhibition zone diameter measurements, the complex exhibited significant antibacterial activity against both Staphylococcus aureus and Escherichia coli. It also exhibited significant antifungal activity against Candida albicans, but no activity was found against Aspergillus flavus . The crystal structure of the Ni(II) complex [C 12 H 20 N 6 Ni O 6 S 2 ], Mr = 467.17, was determined from Cu Kα X-ray diffraction data, λ = 1.54178 A, at 100 K using direct methods. The crystals are monoclinic, space group P2 1 /n with Z = 4 and a = 8.9893(2) A, b = 17.6680(5) A, c = 12.5665(3) A, β = 108.609(1)°. In parallel with this study corresponding results were derived for the crystal structure determined independently from synchrotron X-ray diffraction data, λ = 0.61990 A, at 100 K. The unit cell parameters derived in this experiment are a = 9.000(2) A, b = 17.700(4) A, c = 12.590(3) A, β = 108.61(3)°. Both studies show 4 O and 2 N atoms coordinating Ni in a distorted octahedral arrangement. Each of the Ni 2-hydroxy-pyridinium-N-oxide moieties is highly planar and the S=C=N-Ni ligands are approximately linear. The crystal structure is characterised by a number of strong hydrogen bonds.