Mohamed M. Shoukry

Synthesis, characterization, biological activity and equilibrium studies of metal(II) ion complexes with tridentate hydrazone ligand derived from hydralazine

In the present study, a new hydrazone ligand (2-((2-phthalazin-1-yl)hydrazono)methyl)phenol) prepared by condensation of hydralazine (1-Hydralazinophthalazine) with salicylaldehyde (SAH). The synthesized SAH-hydrazone and its metal complexes have been characterized by elemental analyses, IR, (1)H NMR, solid reflectance, magnetic moment, molar conductance, mass spectra, UV-vis and thermal analysis (TGA). The analytical data of the complexes show the formation of 1:1 [M:L] ratio, where M represents Ni(II), Co(II) and Cu(II) ions, while L represents the deprotonated hydrazone ligand. IR spectra show that SAH is coordinated to the metal ions in a tridentate manner through phthalazine-N, azomethine-N and phenolic-oxygen groups. The ligand and their metal chelates have been screened for their antimicrobial activities using the disc diffusion method against the selected bacteria and fungi. Proton-ligand association constants of (SAH) and the stepwise stability constants of its metal complexes are determined potentiometrically in 0.1 M NaNO(3) at different temperatures and the corresponding thermodynamic parameters were derived and discussed. The order of -ΔG° and -ΔH° were found to obey Mn(2+)<Co(2+)<Ni(2+)<Cu(2+), in accordance with the Irving-Williams order. The complexes were stabilized by enthalpy changes and the results suggest that the complexation is an enthalpy-driven process. The concentration distribution diagrams of the complexes are evaluated.

Complex formation reactions of (N,N′-dimethylethylenediamine) palladium(II) with various biologically relevant ligands

Abstract cis -Dichloro-( N , N ′-dimethylethylenediamine)palladium(II) [Pd(Me 2 en)Cl 2 ] was synthesized and characterized. Stoichiometry and stability constants of the complexes formed between [Pd(Me 2 en)(H 2 O) 2 ] 2+ with various biologically relevant ligands are investigated. The ligands used are dicarboxylic acids, amino acids, peptides and DNA unit constituents. The results showed the formation of 1:1 complexes with amino acids and dicarboxylic acids. Peptides forms both 1:1 complexes and the corresponding deprotonated amide species. DNA constituents form both 1:1 and 1:2 complexes. The concentration distribution of the complexes in solution was evaluated. [Pd(Me 2 en)Cl 2 ] and [Pd(Me 2 en)(CBDCA)] were isolated and characterized by elemental analysis, FTIR, 1 H NMR, mass spectra and thermal analysis (TGA).

Equilibrium and hydrolysis of α-amino acid esters in mixed-ligand complexes withN-(acetamido)-iminodiacetatecopper(II)

SummaryThe formation equilibria of the binary and ternary complexes of CuII withN-(acetamido)-iminodiacetic acid (ADA) and amino acids or their esters were investigated potentiometrically. The chelation mode was ascertained by conductivity measurements. The kinetics of the base hydrolysis of amino acid esters in the presence of the copper(II)-ADA complex were studied. The rate and catalysis constants were estimated.

Equilibrium studies of the diorganotin(IV) complexes with some amino acids and related compounds.

The interaction of dimethyltin(IV) and diethyltin(IV) cations with water and some amino acids and related compounds was investigated at 25 degrees C and ionic strength 0.1 M NaNO(3) using a potentiometric technique. The results showed the formation of 11 and 12 (organotin:ligand) complexes and the corresponding stability constants were determined. The participation of different ligand functional groups in binding to organotin is discussed. The effect of the pK(a) value of the respective ligand on the stability constant of its complex species was elucidated. The concentration distribution of the complexes in solution was evaluated.

Ternary complexes involving copper(II) and amino acids, peptides and DNA constituents. The kinetics of hydrolysis of α-amino acid esters

Binary and ternary complexes of copper(II) involving picolylamine (Pic) and amino acids, peptides (HL) or DNA constituents have been investigated. Ternary complexes of amino acids or peptides are formed by simultaneous reactions. Amino acids form the Cu(Pic)L complex, whereas peptides form Cu(Pic)L and Cu(Pic)(LH−1). The ternary complexes of copper(II) with picolylamine and DNA are formed in a stepwise process, whereby binding of copper(II) to picolylamine is followed by ligation of the DNA components. The stability of the ternary complexes is compared with the stabilities of the corresponding binary complexes. The hydrolysis of glycine methyl ester (MeGly) is catalysed by the Cu(pic)2+ complex. The kinetic data is fitted assuming that the hydrolysis proceeds in two steps. The first step, involving coordination of the amino acid ester by the amino and carbonyl groups, is followed by rate-determining attack by the OH− ion. The second step involves equilibrium formation of the hydroxo-complex, Cu(pic)(MeGly)(OH), followed by intramolecular attack.

Copper(II) complexes of imino-bis(methyl phosphonic acid) with some bio-relevant ligands. Equilibrium studies and hydrolysis of glycine methyl ester through complex formation

Binary and ternary complexes of Cu(II) involving imino-bis(methyl phosphonic acid) (IdP) abbreviated as H4A and some selected bio-ligands, amino acids, peptides and DNA constituents (L), were examined. Cu(II) forms CuA and CuAH complexes with IdP. Ternary complexes are formed in a stepwise mechanism whereby iminodiphosphonic acid binds to Cu(II), followed by coordination of amino acid, peptide or DNA. The concentration distribution of the various complex species has been evaluated. The kinetics of base hydrolysis of glycine methyl ester in the presence of Cu(II)-IdP was studied in aqueous solution at different temperatures, and in dioxane-water solutions of different compositions at 25°C. The activation parameters are evaluated and discussed.

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.

Metal complexes of salicylhydroxamic acid: equilibrium studies and synthesis

SummaryThe complex formation equilibria involved in the binary and ternary systems of MII-SHAM and MII-SHAM-L [M = Cu, Ni, Co, Zn, Cd, Mn, Hg, Ca or UO2; SHAM = salicylhydroxamic acid; L = the ligating agent, N-(2-acetamido)iminodiacetic acid (ADA), iminodiacetic acid (IDA) or nitrilotriacetic acid (NTA)] were investigated by the potentiometric technique at 25 °C and ionic strength 0.1 m NaNO3. The results indicate the formation of 1∶1 and 1∶2 (metal ion:ligand) SHAM complexes. The formation of mixed-ligand complexes followed a stepwise mechanism, whereby an ML complex was first formed, followed by the ligation of SHAM. The relative stability of the mixed-ligand complex was compared with that of the binary complex. The concentration distribution of the complexes possibly formed in solution was evaluated. Solid complexes of SHAM were prepared and characterized by microanalysis, conductivity, i.r., electronic and n.m.r. spectroscopies, and magnetic susceptibility measurements.

Complex-formation reactions and stability constants for mixed-ligand complexes of diaqua(2-picolylamine)palladium(II) with some bio-relevant ligands

The complex-formation reactions of [Pd(Pic)(H2O)2]2+ (pic = 2-Picolylamine) with selected bio-relevant ligands, containing different functional groups, were investigated. Stoichiometry and stability constants for the complexes formed are reported. The results show the formation of 1 : 1 complexes with amino acids and dicarboxylic acids. The effect of chelate ring size of the dicarboxylic acid complexes on their stability constants was examined. Peptides form both 1 : 1 complexes and the corresponding deprotonated amide species. Structural effects of the peptide on the amide deprotonation were investigated. DNA pyrimidinic constituents, such as uracil, uridine, thymidine and thymine, form 1 : 1 and 1 : 2 complexes, whereas purinic constituents, such as inosine 5′-monophosphate (5′-IMP) and guanosine 5′-monophosphate (5′-GMP), form only 1 : 1 complexes. Both DNA constituents and cyclobutane dicarboxylate (CBDCA) react with [Pd(Pic)(H2O)2]2+ forming [Pd(Pic)(CBDCA-O)DNA], where (CBDCA-O) represents cyclobutane dicarboxylate coordinated by one carboxylate oxygen atom. The concentration distribution of the complexes in solution was evaluated. The effect of dioxane on the acid dissociation constants of CBDCA and the formation constant of its complex with Pd(Pic)2+ is reported. The effect of increasing chloride concentration on the formation of the CBDCA complex was investigated.