Mahmoud A. Mohamed

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).

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.

Interaction of dipropyltin(IV) with amino acids, peptides, dicarboxylic acids and DNA constituents

Interaction of dipropyltin(IV) with selected amino acids, peptides, dicarboxylic acids or DNA constituents was investigated using potentiometric techniques. Amino acids form 1 : 1 and 1 : 2 complexes and, in some cases, protonated complexes. The amino acid is bound to dipropyltin(IV) by the amino and carboxylate groups. Serine is complexed to dipropyltin(IV) with ionization of the alcoholic group. A relationship exists between the acid dissociation constant of the amino acids and the formation constants of the corresponding complexes. Dicarboxylic acids form both 1 : 1 and 1 : 2 complexes. Diacids forming five- and six-membered chelate rings are the most stable. Peptides form complexes with stoichiometric coefficients 111(MLH), 110(ML) and 11-1(MLH−1)(tin: peptide: H+). The mode of coordination is discussed based on existing data and previous investigations. DNA constituents inosine, adenosine, uracil, uridine, and thymine form 1 : 1 and 1 : 2 complexes and the binding sites are assigned. Inosine 5′-monophosphate, guanosine 5′-monophosphate, adenosine 5′-monophosphate and adenine form protonated species in addition to 1 : 1 and 1 : 2 complexes. The protonation sites and tin-binding sites were elucidated. Cytosine and cytidine do not form complexes with dipropyltin(IV) due to low basicity of the donor sites. 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.

Equilibrium studies of organotin(IV) complexes with vitamin B6

The complex-formation equilibria of dimethyltin(IV), trimethyltin(IV) and tributyltin(IV) with pyridoxamine were investigated in dioxane-water mixtures and at different temperatures using a potentiometric technique. The stepwise formation constants of the complexes formed in solution were calculated using the non-linear least-square program MINIQUAD-75. The effect of dioxane as a solvent on the protonation constants of pyridoxamine and the formation constants of organotin(IV) complexes was discussed. The thermodynamic parameters DeltaH degrees and DeltaS degrees calculated from the temperature dependence of the equilibrium constants were investigated. The concentration distribution of the various complex species was evaluated as a function of pH.

Complex Formation Reactions of Divinyltin(IV) Complexes with Amino Acids, Peptides, Dicarboxylic acids and Related Compounds

Complex formation equilibria of divinyltin(IV) with amino acids, peptides, and dicarboxylic acids have been investigated. Stoichiometry and stability constants for the complexes formed were determined at 25°C and ionic strength 0.1 M NaNO3. The results showed the formation of ML, MLH, and ML2 (organotin : ligand : hydrogen) complexes with amino acids. Peptides form ML complexes and the corresponding deprotonated amide species MLH−1. In the latter species the binding with divinyltin(IV) occurs through the terminal amino group, carboxylate oxygen, and the amide nitrogen atoms (CO− 2, N− amide, NH2). The results showed the formation of ML and ML2 complexes with dicarboxylic acids. The concentration distribution of the complexes in solution was evaluated. The bonding sites of the divinyltin(IV) complex in solid state with oxalic acid was investigated by means of elemental analyses, FTIR, and mass spectra. Non-isothermal decomposition of the above complex has been studied and the result was statistically analyzed. The main steps were identified for the thermal decomposition reaction and each step proved to be a first order reaction. The kinetic parameters E a and A were calculated for each step in the reaction. The thermodynamic functions H, G, and S* were calculated for each step of the reaction.

Study of chemical bonding, physical and biological effect of metformin drug as an organized medicine for diabetes patients with chromium(III) and vanadium(IV) ions.

New vanadium(IV) and chromium(III) complexes of metformin (MFN) were synthesized upon the chemical interaction between vanadyl(II) sulfate monohydrate or chromium(III) chloride hexahydrate with metformin diabetic drug in the media of a pure grade of methanol solvent. The [(VO)2(MFN)2(SO4)2]2H2O and [Cr(MFN)3]·Cl3·6H2O complexes were discussed using microanalytical measurements, molar conductance, spectroscopic (infrared, ESR, XRD, and UV-vis), effective magnetic moment, scanning electron microscopy (SEM), and thermal analyses (TG/DTG). The elemental analysis shows that VO(II) and Cr(III) complexes were associated with 1:1 and 1:3M ratios, respectively. The infrared spectroscopic results data received from the comparison between free MFN free ligand and their vanadyl(II) and chromium(III) complexes were proven that metformin reacted with respected metal ions as a bidentate ligand through its two imino groups. The kinetic thermodynamic parameters were estimated from the DTG curves. The microstructure changes of the VO(II) and Cr(III) complexes have been probed using positron annihilation lifetime (PAL) and positron annihilation Doppler broadening (PADB) techniques. The PAL and PADB line-shape parameters were found to be dependent on the structure, electronic configuration and molecular weight of metal complexes. Antimicrobial activity of the metformin free ligand and its vanadyl(II) and chromium(III) complexes were evaluated against the gram negative and gram positive bacteria strains and different fungal strains. Moderate antimicrobial activity recorded by disk diffusion inhibition growth zone method in vanadyl(II) and chromium(III) complexes compared to metformin free ligand.

Synthesis, characterization, and antimicrobial activities of barbital-based alkaline earth metal complexes: the X-ray crystal structure of [Ba2H(Barb)5] (Barb = 5,5-diethyl barbiturate)

Three barbital-based alkaline earth metal complexes, [Ca(Barb)2] · 3H2O (1), [Ba2H(Barb)5] (2) and [Mg(Barb)2] · 2H2O (3) (Barb = 5,5-diethyl barbiturate sodium salt), were synthesized and characterized with elemental analysis, thermal analysis, and infrared, Raman, ultraviolet, and NMR (1H and 13C) spectroscopies. Single-crystal X-ray diffraction studies reveal that 2 is a dimer. Each barium(II) is surrounded by an O7N2 donor set in an approximate monocapped square antiprism with Ba–O distances ranging from 2.6512(14) to 2.9168(15) Å and Ba–N distances of 2.7601(15) and 3.2558(17) Å. The complex forms polymeric networks in the solid state with different coordinating abilities of O and N donors and N–H···O hydrogen bonds. The antimicrobial activities of 1–3 were observed against different gram-positive and gram-negative bacteria, yeast, and molds. Variable antimicrobial activity against the different bacteria strains was observed and compared with that of standard antibiotics; minimum inhibitory concentration values ranged from 22 to 170 µg mL−1 for bacteria.

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.

Complex Formation Reactions of Dimethyltin(IV) with Some Zwitterionic Buffers

Equilibrium studies in aqueous solution are reported for dimethyltin(IV) complexes of zwitterionic buffers, such as bicine and tricine (L). Stoichiometry and stability constants for the complexes formed were determined at 25°C and ionic strength 0.1M NaNO3. The results showed the best fit of the titration curves were obtained for complexes MLH, ML, ML2, MLH-1, and MLH-2 with the hydrolysis products of the dimethyltin(IV) cation. The bonding sites of the dimethyltin(IV) complexes with bicine and tricine at different pH were characterized in the solid state by elemental analyses, FTIR, and TG analysis. The molecular formula of the complexes synthesized at pH=3.0 is [(CH3)2Sn(L)(H2O)]Cl while in neutral and alkaline media the hydrolytic species are formed.