Search

The interaction of diethylltin(IV) (DET) and divinyltin(IV) (DVT) with 1-(2-aminoethyl)-pyrrolidine (AEPY) was investigated using potentiometric technique at ionic strength of 0.1 mol dm −3 NaNO 3 . The hydrolysis constants of diethyltin(IV) and divinyltin(IV) cations and the stepwise formation constants of the complexes formed in solution were calculated at different temperatures and in solutions of dioxane-water solutions of different compositions. The stoichiometry and stability constants for the complexes formed were reported. The results showed the formation of 1:1 complex and the corresponding hydroxo complexes. The concentration distributions of the various complex species were evaluated as a function of pH. The thermodynamic parameters ΔH° and ΔS° calculated from the temperature dependence of the equilibrium constants were investigated for DET and DVT complexes with AEPY. The equilibrium constant for the displacement of 1-(2-aminoethyl)-pyrrolidine coordinated to diorganotin(IV) by thymine and thymidine as representative examples of DNA constituents was calculated from calculations based upon equilibrium properties. The results are expected to contribute to the chemistry of tin(IV) based anticancer agents. [ABSTRACT FROM AUTHOR]

A combined experimental and computational study of novel mixed ligand Cu(II), Ni(II), Co(II), Mn(II), Zn(II), Fe(III) and Cr(III) complexes of tenoxicam drug (H 2 Ten) and valine (Val) have been reported. The complexes have been characterized using elemental analyses, molar conductance, IR, UV–Vis, magnetic moment, diffused reflectance, thermal analysis and X-ray powdered diffraction. IR and UV–Vis spectra confirm that H 2 Ten behaves as a neutral bidentate ligand co-ordinated to the metal ions via the pyridine-N and carbonyl group of the amide moiety. Quantum chemical calculations were performed with semi-empirical method to find the optimum geometry of complexes. Also, valuable information is obtained from calculations of molecular parameters for all complexes including net dipole moment of the metal complexes, values of binding energy, which proved that the complexes are more stable than the free ligand. X-ray powder diffraction is used as a new tool to estimate the crystallinity of chelates as well as to elucidate their geometrical structures. The protonation equilibria of tenoxicam (H 2 Ten) formed in DMSO-water solution were calculated using the nonlinear least-squares program MINIQUAD-75. The concentration distribution of the various species has been evaluated. The effect of DMSO as a solvent on the protonation constants of H 2 Ten was discussed. The thermodynamic parameters ΔH o and ΔS o calculated from the temperature dependence of the equilibrium constants were investigated. The humeral immune response of calves vaccinated with inactivated IBR vaccine and ternary M-H 2 Ten-Val chelates was evaluated. Molecular docking was used to predict the binding between tenoxicam and the receptors of prostate cancer mutant 2q7k-hormone, breast cancer mutant 3hb5-oxidoreductase, crystal structure E. coli (3T88) and crystal structure of S. aureus (3q8u). [ABSTRACT FROM AUTHOR]

Protonation constants of novel thiosemicarbazones including 2-(1-(2-phenyl-hydrazono)-propan-2-ylidene) hydrazine-carbothioamide (TPHP) and N -methyl-2-(1-(2-phenyl-hydrazono)-propan-2-ylidene)hydrazinecarbo-thioamide (MTPHP) ligands and their corresponding metal-ligand formation constants with Cu(II), Ni(II), Mn(II) and Co(II) ions were determined at 15 °C, 25 °C and 35 °C in 50% DMSO solution at I = 0.1 mol·dm − 3 NaNO 3 . The stability order of complexes with reference to the metal ions has been followed this order Cu(II) > Ni(II) > Co(II) > Mn(II) in concord with the Irving-Williams stability order. Also, chemical equilibrium studies indicated that substitution of hydrogen in thiosemicarbazone (TPHP) by methyl group causes lowering of acidity as a result of the electron-releasing effect of the methyl group in the substituted amino group of the thiosemicarbazide moiety. The speciation of different species in solution has been evaluated as a function of pH. Additionally, the effect of temperature on protonation of thiosemicarbazone ligands and formation of their M(II)-thiosemicarbazone complexes was investigated. The thermodynamic parameters (ΔH, ΔS and ΔG) were calculated and discussed. It was found that both log K 1 and –ΔH 1 , for M(II)-thiosemicarbazone complexes are somewhat larger than log 10 K 2 and –ΔH 2 , indicating a change in the dentate character of these ligands from tridentate (SNN-donors) in 1:1 chelates to bidentate (SN-donors) in 1:2; M:L chelates. Also, the lower values of log 10 K 2 and –ΔH 2 than log K 1 and –ΔH 1 may be attributed to steric hindrance produced by the entrance of a second molecule. [ABSTRACT FROM AUTHOR]

As a model for forecasting the ligand properties of antibiotics in living organisms , formation equilibria of binary and ternary Cu(II) complex with Cephradine (Cep) antibiotic in presence of α-alanine (α-Ala) and β-alanine (β-Ala) amino acids have been studied using the potentiometric titrations. Many factors were investigated like the formation constant, protonation constant, composition and stabilities of the species formed with copper(II) ions in water and water-ethanol solutions of different compositions. The thermodynamics were calculated and the data clarified. The pH-titrations of the reaction mixtures have been revealed 1:1:1 (Cu:Cep:amino acid (AA)) ternary complex formation. By aid of Δ log 10 K , Δ log 10 β and log 10 X parameters, quantitative matching of the stability of mixed-ligand complexes and the stability of the binary complexes was done. Investigations of the stability of the ternary complexes relative to their corresponding binary complexes indicated that formation of ternary complexes is more preferable than binary metal complexes. The obtained data from protonation of the investigated cephradine antibiotic and β-Ala/α-Ala amino acids and their complex formation equilibria will be a significant contribution to workers carrying out mechanistic studies in biological media. • Studying the Formation equilibria of binary and ternary Cu(II) complex with Cephradine (Cep) antibiotic in presence of amino acids. • (logβ) were determined potentiometrically along a broad range of solvent composition. • The speciation of different species in solution was assessed. • The effect of temperature on protonation of ligands and formation of mixed-ligand complexes was studied. [ABSTRACT FROM AUTHOR]