Mohamed R. Shehata

Synthesis, characterization, equilibrium study and biological activity of Cu(II), Ni(II) and Co(II) complexes of polydentate Schiff base ligand

Schiff base ligand, 1,4-bis[(2-hydroxybenzaldehyde)propyl]piperazine (BHPP), and its Cu(II), Ni(II) and Co(II) metal complexes were synthesized and characterized by elemental analysis, magnetic susceptibility, molar conductance and spectral (IR and UV-vis) studies. The ground state of BHPP ligand was investigated using the BUILDER module of MOE. Metal complexes are formed in the 1:1 (M:L) ratio as found from the elemental analysis and found to have the general formula [ML]·nH(2)O, where M=Co(II), Ni(II) and Cu(II), L=BHPP. In all the studied complexes, the (BHPP) ligand behaves as a hexadentate divalent anion with coordination involving the two azomethine nitrogens, the two nitrogen atoms of piperazine ring and the two deprotonated phenolic OH-groups. The magnetic and spectral data indicates octahedral geometry of metal(II) complexes. The ligand and their metal chelates have been screened for their antimicrobial activities using the disc diffusion method against the selected bacteria and fungi. They were found to be more active against Gram-positive than Gram-negative bacteria. Protonation constants of (BHPP) ligand and stability constants of its Cu(2+), Co(2+) and Ni(2+) complexes were determined by potentiometric titration method in 50% DMSO-water solution at ionic strength of 0.1 M sodium nitrate. It has been observed that the protonated Schiff base ligand (BHPP) have four protonation constants. The divalent metal ions Cu(2+), Ni(2+) and Co(2+) form 1:1 complexes.

TRIMETHYLTIN(IV) COMPLEXES WITH SOME SELECTED DNA CONSTITUENTS

Abstract The interaction of the trimethyltin(IV) with some selected DNA constituents such as inosine, inosine 5′-monophosphate, adenine, adenosine, adenosine 5′-monophosphate, uracil, thymine, thymidine, cytosine and cytidine were investigated at 25°C and 0.1 M ionic strength in aqueous solutions and dioxane-water mixtures using potentiometry. The stepwise formation constants of the complexes formed in solution were calculated using the non-linear least-square program MINIQUAD-75. The concentration distribution of the various complex species was evaluated as a function of pH. The effect of dioxane as a solvent on the protonation constants of ligands and the formation constants of trimethyltin(IV) complexes were discussed. The thermodynamic parameters ΔH° and ΔS° calculated from the temperature dependence of the equilibrium constants were investigated.

Mixed ligand complexes of diaquo (2,2¢-bipyridine)palladium(II) with cyclobutane-1,1-dicarboxylic acid and DNA constituents

Complex formation equilibria involving [Pd(bpy)(H2O)2]2+ (bpy = 2,2′-bipyridine) and the cyclobutanedicarboxylate ligand (cbdca), ethylenediamine and DNA have been investigated. Mixed ligand complexes of [Pd(bpy)(cbdca)] with inosine, inosine-5′-monophosphate (5′-IMP), uracil, uridine and adenine have been studied. The results show ring opening of the cbdca and monodentate chelation of the DNA components. Stoichiometries and stability constants for the complexes were determined at 25 °C and at constant 0.1 M ionic strength (adjusted using NaNO3). The coordination sites were found to be pH-dependent. The [Pd(bpy)Cl2], [Pd(bpy)(cbdca)] and [Pd(bpy)(inosine)](NO3) complexes were isolated.

Equilibrium Studies of Mixed Ligand Complexes Involving (1,2-Diaminopropane)-Palladium(II) and Some Bioligands

Summary. Complex formation equilibria have been investigated for [Pd(DAP)(H2O)2]2+ (DAP=1,2-diaminopropane) with Cl−, OH−, cyclobutanedicarboxylic acid (CBDCAH2), amino acids, peptides, and DNA units. Stoichiometries and stability constants of the complexes were determined at 25°C and constant ionic strength (0.1 M NaNO3). The results showed the formation of 1:1 complexes with amino acids and CBDCAH2. Peptides formed both 1:1 complexes and the corresponding deprotonated amide species. DNA constituents formed both 1:1 and 1:2 complexes. Pd(DAP)(CBDCA)ċH2O was isolated and characterized. The concentration distribution of the complexes in solution was evaluated.Zusammenfassung. Die Komplexbildungsgleichgewichte von [Pd(DAP)(H2O)2]2+ (DAP=1,2-Diaminopropan) mit Cl-, OH-, Cyclobutandicarbonsäure (CBDCAH2), Aminosäuren, Peptiden und DNA-Basen wurden untersucht. Die Stöchiometrien und die Gleichgewichtskonstanten der Komplexe wurden bei 25°C und einer konstanten Ionenstärke von 0.1 M NaNO3 bestimmt. Die Ergebnisse zeigen, daß mit Aminosäuren und CBDCAH2 Komplexe der Zusammensetzung 1:1 gebildet werden. Peptide ergeben sowohl 1:1-Komplexe als auch die entsprechenden deprotonierten Amidspecies. Mit DNA-Basen erhält man 1:1- und 1:2-Komplexe. Pd(DAP)(CBDCA)ċH2O wurde isoliert und charakterisiert. Die Konzentrationsverteilung der Komplexe in Lösung wurde ermittelt.

Coordination properties of 6-aminopenicillanic acid: binary and ternary complexes involving biorelevant ligands

Formation equilibria of copper(II) complexes of 6-aminopenicillanic acid (APA) and the ternary complexes Cu(APA)B (B = glycine, alanine, valine, isoleucine, phenylalanine, proline, hydroxyproline, serine, threonine, ornithine, histidine, methionine, glycylglycine and inosine) were investigated at 25°C and 0.1 M ionic strength. The speciation of the complexes was resolved. Values of Δlog K, log X and log βstat indicate a large enhancement of the stability of the mixed ligand complexes. The effects of temperature and organic solvent on the dissociation constant of APA and the formation constant of Cu(APA) were studied and thermodynamic parameters were calculated. The solid complex of Cu(APA)Cl·2H2O was separated and identified by elemental analysis and infrared spectroscopy. In the complex APA is coordinated to copper(II) through the amino group and β-lactam carbonyl oxygen. Absorption spectra of the binary complexes of copper(II) and APA were also investigated.

Synthesis and tautomeric structure of the azo-coupling products of 2 -methyl-7-phenylpyrimido[1,2-b][1,2,4 ]triazepine -4,9 (3h,5h)-dione

A simple synthetic strategy is described for synthesis of 3-arylazo-2-methyl-7-phenylpyrimido[1,2-b][1,2,4]triazepine-4,9-diones 4a–j. The acid dissociation constants were determined for the series prepared and were correlated by a Hammett-type equation using enhanced substituent constants. The results of such correlation together with the spectral data, including 15N isotopic labelling, indicated that the studied compounds exist predominantly in the hydrazone tautomeric form.

Interaction of dimethyltin(IV) and trimethyltin(IV) with dehydroacetic acid.

Abstract The interaction of trimethyltin(IV) and dimethyltin(IV) with dehydroacetic acid was investigated at 25°C and 0.1 M ionic strength in 20% dioxane–water mixture. The stepwise formation constants of the complexes formed in solution were calculated using the non-linear least-square program MINIQUAD–75. The concentration distribution of the various complex species was evaluated as a function of pH.

Mono- and binuclear complexes involving [Pd(N,N-dimethylethylenediamine)(H2O)2]2+, 4,4′-bipiperidine and DNA constituents

The Pd(dmen)Cl2, where dmen = N,N-dimethethylenediamine, was synthesized and characterized by elemental analysis and spectroscopy. The complex-formation equilibria in the reaction of [Pd(dmen)(H2O)2]2+ with 4,4′-bipiperidine (Bip) and DNA constituents were investigated at 25°C and 0.1 mol L−1 ionic strength. The results show the formation of [(H2O)(dmen)Pd(Bip)Pd(dmen)(H2O)]4+. Inosine, uracil, and thymine interact with the previously mentioned complex by the substitution of two-coordinated water molecules. The formation constants of all possible mono- and binuclear complexes were determined and their speciation diagrams were evaluated.

Binary and Ternary Complexes of Cd(II) Involving Triethylenetetramine and Selected Amino Acids and DNA Units

The formation equilibria of the binary complex of cadmium(II) with triethylenetetramine (Trien) and of ternary complexes Cd(Trien)L, where L refers to amino acids, DNA constituents and related compounds have been investigated. Cd(II) was found to form a highly stable complex with Trien. The acid-base equilibria of Cd(Trien)2+ were characterized. Ternary complexes of amino acids and DNA constituents are formed through stepwise mechanism, whereby Trien binds to Cd(II), followed by interaction with ligand (L), whereas thiol-containing ligands form ternary complexes through a simultaneous mechanism. The formation constants of the complexes were determined at 25 °C and μ, = 0.1M NaNO3. The participation of different ligand functional groups in the complex-formation was examined.

Thermodynamic Investigation and Mixed Ligand Complex Formation of 1,4-Bis-(3-aminopropyl)-piperazine and Biorelevant Ligands

Thermodynamic parameters for protonation of 1,4-bis(3-aminopropyl)-piperazine (BAPP) and its metal complexation with some divalent metal ions were determined in aqueous solution at constant ionic strength (0.1 M NaNO3) using a potentiometric technique. The order of –ΔG0 and –ΔH0 was found to obey Co2+ < Ni2+ < Cu2+ > Zn2+, in accordance with the Irving-Williams order. The formation equilibria of zinc (II) complexes and the ternary complexes Zn(BAPP)L, where L = amino acid, amides, or DNA constituents), have been investigated. Ternary complexes are formed by a simultaneous mechanism. The concentration distribution of the complexes in solution was evaluated as a function of pH. Stoichiometry and stability constants for the complexes formed are reported and discussed. The stability of ternary complexes was quantitatively compared with their corresponding binary complexes in terms of the parameter Δlog K.