Alaa E. Ali

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.

Synthesis, computational, spectroscopic, thermal and antimicrobial activity studies on some metal-urate complexes

New sixteen uric acid metal complexes of different stoichiometry, stereo-chemistries and modes of interactions were synthesized using different metals Cr, Mn, Fe, Co, Ni, Cu, Cd, UO(2), Na and K. The synthesized complexes were characterized by elemental analysis, spectral (IR, UV-Vis and ESR) methods, thermal analysis (TG, DTA and DSC) and magnetic susceptibility studies. Molecular modeling calculations were used to characterize the ligation sites of the free ligand. Furthermore, quantum chemical parameters of uric acid such as the energies of highest occupied molecular orbital (E(HOMO)), energies of lowest unoccupied molecular orbital (E(LUMO)), the separation energy (ΔE=E(LUMO)-E(HOMO)), the absolute electronegativity, χ, the chemical potential, P(i), the absolute hardness, η and the softness (σ) were obtained for uric acid. Eight different microbial categories were used to study the antimicrobial activity of the free ligand and ten of its complexes. The results indicate that the ligand and its metal complexes possess antimicrobial properties. The stoichiometry of iron-uric acid complex was studied by using different spectrophotometric methods.

Synthesis and Characterization of Amino Alcohol Complexes

Thirty-eight amino alcohol complexes were prepared and analyzed in the mole ratios 1 ; 1, 1 ; 2 and 2 3 (M ; L). The IR spectra proved that coordination occurs via oxygen nitrogen atoms of the ligands. The nujol mull electronic absorption spectra and the room temperature magnetic moment values proved that the complexes are of O h and T d geometry. All complexes, except those of Zn II , Cd II and Hg II are high spin with the existence of a Cu-Cu interaction in the copper complexes. The ESR parameters are calculated including the c-bond parameter ( f 2 ) and the fraction of 3 d character in the Cu II 3 d -4S ground state ( f 2 ) of the axial compressed triethanolamine complexes.

Effect of cadmium and zinc ethanolamine complexes on rat brain monoamine oxidase-B activity in vitro

Monoamine oxidase-B (MAO-B) from rat brain was inhibited strongly by the prepared cadmium and zinc ethanolamine complexes obtained from their sulphate and chloride salts. The inhibition of MAO-B by these complexes was time-dependent and fully reversible after dilution and sedimentation. In vitro, the cadmium ethanolamine complexes were more potent at inhibiting MAO-B than the zinc complexes. The inhibitory effect of these complexes follow the order: TEA>DEA>MEA, due to the alkyl residues and steric effect properties. The inhibition of MAO-B by cadmium and zinc ethanolamine complexes was a noncompetitive type. The K(i) values were calculated. The influence of the complexes on the activity of MAO-B was rather evaluated. It decreased the MAO-B activity. The IC(50) values of the two potent cadmium and zinc triethanolamine complexes on MAO-B were evaluated indicating that the complexes were tightly binding, but reversible inhibitors for MAO-B. In general, these systems may be used for preventing some neurodegenerative diseases.

Spectroscopic studies on gallic acid and its azo derivatives and their iron(III) complexes

Azo gallic derivatives and their iron(III) complexes were synthesized and characterized. The stereochemistry and the mode of bonding of the complexes were achieved based on elemental analysis, UV-Vis and IR. The thermal behaviors of the complexes were studied. The effect of pH on the electronic absorption spectra of gallic acid and its azo derivatives are discussed. Different spectroscopic methods (molar ratio, straight line method, continuous variation, slope ratio and successive method) are applied for determination of stoichiometry and pK values for the complex formation of gallic acid with iron(III) in aqueous media. Iron(III) complexes of gallic acid is formed with different ratio: 1:1, 1:2, 1:3 and 1:4 (M:L).

Solvatochromic behavior of the electronic absorption spectra of gallic acid and some of its azo derivatives

The electronic absorption spectra of gallic acid and its azo derivatives have been studied in various solvents of different polarities. Multiple regression techniques were applied to calculate the regression and correlation coefficients based on an equation that relates the wavenumbers of the absorption band maxima (υ(max)(-)) to the solvent parameters; refractive index (n), dielectric constant (D), empirical Kamlet-Taft solvent parameters, π*(dipolarity/polarizability), α (solvent hydrogen-bond donor acidity) and β (solvent hydrogen-bond acceptor basicity). The fitting coefficient obtained from this analysis allows estimating the contribution of each type of interactions relative to total spectral shifts in solution. The dependence of υ(max)(-) on the solvent parameters indicates that the obtained bands are affected by specific and non-specific solute-solvent interactions.

STUDIES ON SOME THIAZOLYLAZO COMPOUNDS AND THEIR COBALT, NICKEL, AND COPPER COMPLEXES

ABSTRACT The thiazolylazo compounds and their Co(II), Ni(II) and Cu(II) complexes of barbituric acid, uracil, thiouracil, citrazinic acid, chromotropic acid, gallic acid, pyrogallol and salicylic acid were prepared and characterized by 1H NMR, IR and the effect of pH on the electronic absorption spectra. The mode of ionization, the electronic transitions and the dissociation constants were discussed. The stoichiometries of the complexes were of 1:1, 2:1 and 3:2 (M:L). The copper complexes are of isotropic ESR spectra (except that of gallic acid which showed a complicated one) and are of magnetically diluted behaviour with orbital contribution. Detailed DTA data were obtained and discussed.

Spectral, coordination and thermal properties of 5-arylidene thiobarbituric acids

Synthesis of 5-arylidine thiobarbituric acids containing different functional groups with variable electronic characters were described and their Co(2+), Ni(2+) and Cu(2+) complexes. The stereochemistry and mode of bonding of 5-(substituted benzylidine)-2-TBA complexes were achieved based on elemental analysis, spectral (UV-VIS, IR, (1)H NMR, MS), magnetic susceptibility and conductivity measurements. The ligands were of bidentate and tridentate bonding through S, N and O of pyrimidine nucleolus. All complexes were of octahedral configuration. The thermal data of the complexes pointed to their stability. The mechanism of the thermal decomposition is discussed. The thermodynamic parameters of the dissociation steps were evaluated and discussed.

Synthesis, spectral, thermal and antimicrobial studies of some new tri metallic biologically active ceftriaxone complexes

Iron, cobalt, nickel and copper complexes of ceftriaxone were prepared in 1:3 ligand:metal ratio to examine the ligating properties of the different moieties of the drug. The complexes were found to have high percentages of coordinated water molecules. The modes of bonding were discussed depending on the infrared spectral absorption peaks of the different allowed vibrations. The Nujol mull electronic absorption spectra and the magnetic moment values indicated the Oh geometry of the metal ions in the complexes. The ESR spectra of the iron, cobalt, and copper complexes were determined and discussed. The thermal behaviors of the complexes were studied by TG and DTA techniques. The antimicrobial activities of the complexes were examined and compared to that of the ceftriaxone itself.

Thermal properties of mercury(II) and palladium(II) purine and pyrimidine complexes

Six solid Pd(II) and Hg(II) complexes of some purines and pyrimidines have been prepared and characterized by elemental analyses, IR, UV–Vis spectra, magnetic measurements, and thermal analyses. The data suggest tetrahedral and square planar geometries for mercury and palladium complexes, respectively. The thermal behavior of the complexes has been studied applying TG, DTA, and DSC techniques, and the thermodynamic parameters and mechanisms of the decompositions were evaluated. The ∆S* values of the decomposition steps of the metal complexes indicated that the activated fragments have more ordered structure than the undecomposed complexes, and/or the decomposition reactions are slow. The thermal processes proceeded in complicated mechanisms where the bond between the central metal ion and the ligands dissociates after losing small molecules such as H2O, HCl or C=O. The palladium adenine complex is ended with the metal as a final product. However, the thermal reactions of the other five palladium and mercury pyrimidines complexes are ended with metal bonded to O, N, or S of the pyrimidine ring.