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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]

Binary and ternary complex formation equilibria of copper(II) with imidazole-4-acetic acid (IMA) and some aromatic amino acids such as tryptophan and phenylalanine have been studied from 15 to 45 °C by potentiometric titration. The pH-titrations of the reaction mixtures have shown 1:1:1 (Cu:IMA:amino acid) ternary complex formation. The stability of mixed-ligand complexes was quantitatively compared with the stability of the binary complexes as Δlog K, Δlog β and log X parameters. The speciation of different species in solution has been evaluated as a function of pH. The effect of temperature on protonation of the ligands and formation of mixed ligand complexes was investigated. Thermodynamic parameters were calculated and are discussed. The effect of solvent of the protonation of IMA and Cu-IMA complex formation was also investigated and discussed. Additionally, the stoichiometric protonation constants (log β) of imidazole-4-acetic acid and its binary Cu(II)-IMA complexes were determined potentiometrically over a wide range of solvent composition. [ABSTRACT FROM AUTHOR]

The formation of mixed ligand complexes of Cu(II) with 2,2′-bipyridyl (Bipy) in the presence of some selected aromatic diamines (L) (L = 3,4-diamino benzoic acid (DABA), 2-hydazinopyridine (hzpy) or 4-chloro- o-phenylenediamine has been studied by pH-metric titrations. Potentiometric measurements show that ternary complexes are formed in a simultaneous manner. The pH-titrations of the reaction mixtures are shown to yield 1:1:1 ternary complex formation. The equilibrium and formation constants of the resulting ternary complexes have been calculated at I = 0.1 mol·dm of NaNO. The order of stability in terms of the secondary ligands has been found to be DABA > hzpy > CAPA. The stability of ternary complexes was quantitatively compared with their corresponding binary complexes in terms of the parameters Δlog K, Δlog β and log X. The concentration distributions of various species formed in solution were also evaluated as a function of pH. In addition, the effect of temperature on both the ionization process of the ligands and complex formations for Cu-Bipy-L ternary systems was studied. The thermodynamic parameters were calculated from the temperature dependence of the equilibrium constants and are discussed. The structure of the Cu(II) complexes have been geometrically optimized using the parameterized PM3 semiempirical method. [ABSTRACT FROM AUTHOR]

Highlights: [•] Transition metal complexes with cetirizine (CTZ) were synthesized and characterized. [•] Protonation equilibria were calculated for (CTZ) and thermodynamics were discussed. [•] Complex formation equilibria and speciation of binary M(II)–CTZ were investigated. [•] The biological activity of the free CTZ and its metal-chelates were investigated. [ABSTRACT FROM AUTHOR]

Proton-ligand association constants of imidazole-4-acetic acid (IMA) were determined potentiometrically in aqueous solution at different temperatures in the range 15-35 °C. The stepwise stability constants of IMA with some selected bivalent transition metal ions were also determined in 0.1 mol·dm NaNO. The stability of the complexes follows the trend Cu > Ni > Co > Mn, which is in agreement with the Irving-Williams order of the metal ions. The thermodynamic parameters for Cu(II)-IMA complex formation were derived and discussed. The ternary complexes Cu(IMA)L (IMA = imidazole-4-acetic acid, HL = amino acid, amides or DNA constituents) have been investigated. Ternary complexes of amino acids or amides are formed by a simultaneous mechanism. Amino acids form the complex Cu(IMA)L, whereas amides form two complex species Cu(IMA)L and Cu(IMA)(LH). The DNA constituents form both 1:1 and 1:2 complexes. The stabilities of ternary complexes are quantitatively compared with their corresponding binary complexes. The concentration distribution of the complexes in solution was evaluated as a function of pH. [ABSTRACT FROM AUTHOR]

The protonation constants of some α-amino acids (glycine (Gly), l-alanine (Ala), l-valine (Val), l-serine (Ser), l-leucine (Leu) and l-isoleucine (Ile)) were studied in water and DMSO-water solution mixtures containing 30, 50 and 70 vol-% DMSO; in addition the complex formation equilibria of their copper(II) complexes were studied by potentiometric technique using a combined pH electrode system calibrated in concentration units of the hydrogen ion at 25 ± 0.1 °C under a nitrogen atmosphere, and at an ionic strength of 0.10 mol·dm NaNO. The protonation constants and the overall stability constants of copper(II) complexes were influenced by changes in solvent composition, and their variations are discussed in terms of solvent and structural properties. [ABSTRACT FROM AUTHOR]

The interaction of trimethyltin(IV) (TMT) with imino-bis(methylphosphonic acid) (IDP), abbreviated as HL, was investigated at 25 °C and at ionic strength 0.1 mol⋅dm (NaNO) using a potentiometric technique. The formation constants of the complexes formed in solution were calculated using the nonlinear least-squares program MINIQUAD-75. The stoichiometry and stability constants are reported for the complexes formed. The results show the formation of 110, 111, 112 and 11-1 complexes for the TMT-IDP system. The concentration distribution of the various complex species was evaluated. The effect of dioxane as a solvent, on both the protonation constants and the formation constants of trimethyltin(IV) complexes with IDP, is discussed. The thermodynamic parameters Δ H and Δ S calculated from the temperature dependence of the equilibrium constants were evaluated. The effect of ionic strength on the protonation constants of IDP is also discussed. [ABSTRACT FROM AUTHOR]

Formation equilibria of cobalt(II) complexes of 2-(aminomethyl)-benzimidazole (AMBI) and the ternary complexes Co(AMBI)L (L = aliphatic or aromatic dicarboxylic acids) were investigated in aqueous solutions at 25 °C and 0.1 mol⋅dm ionic strength. Stoichiometry and stability constants are reported for the complexes formed. The speciation of the complexes was resolved. Values of $\log_{10}\ (K_{\mathrm{Co(AMBI)L}}^{\mathrm{Co(AMBI)}})$ and Δlog K are calculated and discussed. The effect of chelate ring size of the dicarboxylic acid complexes on their stability constants was examined. The effect of temperature on the dissociation constant of AMBI, CBDCA, and the formation constant of Co(AMBI) and Co(AMBI)-CBDCA complexes was studied and the thermodynamic parameters were calculated. Formation of the metal complexes has been found to be spontaneous, exothermic and entropically favorable. The solid complexes of [Co(AMBI)L] (L = oxalic acid, 1,1-cyclobutanedicarboxylic acid (CBDCAH) and malonic acid) have been synthesized and characterized by elemental analysis, infrared, spectra, magnetic and conductance measurements. Electronic spectra and μ values suggest a tetrahedral geometry for Co(II)-complexes. The isolated metal chelates have been screened for their antibacterial activities and the complexes show a significant antibacterial activity against Pseudomonas fluorescence (Gram −ve) and Bacillus subtilis (Gram +ve). The activity increases at higher concentration of the compounds. [ABSTRACT FROM AUTHOR]

Abstract: The formation equilibria of copper(II) complexes and the ternary complexes Cu(PDC)L (PDC=2,6-bis-(hydroxymethyl)-pyridine, HL=amino acid, amides or DNA constituents) have been investigated. Ternary complexes are formed by a simultaneous mechanism. The results showed the formation of Cu(PDC)L, Cu(PDC, H−1)(L) and Cu(PDC, H−2)(L) complexes. The concentration distribution of the complexes in solution is evaluated as a function of pH. The effect of dioxane as a solvent on the protonation constant of PDC and the formation constants of Cu(II) complexes are discussed. The thermodynamic parameters and calculated from the temperature dependence of the equilibrium constants are investigated. [Copyright &y& Elsevier]

The interaction of diethyltin(IV), DET, with selected bioligands having a variety of model functional groups was investigated at 25 °C and ionic strength 0.1 mol·dm −3 NaCl using the potentiometric technique. The hydrolysis constants of the DET cation and the formation constants of the complexes formed in solution were calculated using the MINIQUAD-75 program. The stoichiometry and stability constants for the complexes formed are reported. The results show the formation of 1:1 and 1:2 complexes with amino acids and DNA constituents. The dicarboxylic acids form 1:1 complexes. The peptides form both 110 complexes and the corresponding deprotonated amide species [Et 2Sn(LH −1)] (11-1). The participation of different ligand functional groups in binding to organotin is discussed. The concentration distributions of the various complex species were evaluated as a function of pH. The standard thermodynamic parameters Δ H° and Δ S°, calculated from the temperature dependence of the equilibrium constants, were investigated for the interaction of DET with thymine as a representative example of DNA constituents. The effect of ionic strength and solvent on hydrolysis constants of DET, protonation equilibria of thymine and its complex formation with DET were investigated and discussed. [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]

The stoichiometry and stability constants of the complexes formed between [Pd(MAMP)(HO)] and various biologically relevant ligands containing different functional groups were investigated. The ligands used are amino acids, peptides and DNA constituents. The results show the formation of 1:1 complexes with amino acids and peptides and the corresponding deprotonated amide species. Structural effects of peptides on amide deprotonation were investigated. The purine and pyrimidine bases uracil, uridine, cytosine, inosine, inosine 5′-monophosphate (5′-IMP) and thymine form 1:1 and 1:2 complexes. The concentration distribution of the various complex species was calculated as a function of pH. The effect of chloride ion concentration on the formation constant of CBDCA with Pd(MAMP) was also reported. The results show ring opening of CBDCA and monodentate complexation of the DNA constituent with the formation of [Pd(MAMP)(CBDCA-O)DNA], where (CBDCA-O) represents cyclobutane dicarboxylate coordinated by one carboxylate oxygen. The equilibrium constant of the displacement reaction of coordinated inosine, as a typical DNA constituent, by SMC and/or methionine was calculated. The results are expected to contribute to the chemistry of antitumor agents. The calculated parameters of the optimized complexes support the measured formation constants. [ABSTRACT FROM AUTHOR]

Mononuclear copper(II), cobalt(II) and nickel(II) complexes of cetirizine (CTZ = 2-[2-[4-[(4-chlorophenyl)phenyl methyl]-piperazine-1-yl]-ethoxy]acetic acid) in the presence of 2-aminomethyl-benzimidazole·2HCl (AMBI), as a representative example of heterocyclic bases, were synthesized and studied by different physical techniques. All mixed-ligand complexes have been fully characterized with the help of elemental analyses, molecular weight determinations, molar conductance, magnetic moments and spectroscopic data. The formulae of the isolated complexes are [M(AMBI)(CTZ)(NO)(HO)]· nHO where AMBI is the neutral bidentate 2-aminomethylbenzimidazole, CTZ the deprotonated cetirizine and n = 1 for Co(II) or 0 for Cu(II) and Ni(II) complexes. The measured molar conductance values in DMSO indicate that the complexes are non-electrolytes. The formation equilibria of the ternary complexes have been investigated. Ternary complexes are formed by a simultaneous mechanism. Stoichiometry and stability constants for the complexes formed are reported. The concentration distribution of the complexes in solution was evaluated as a function of pH. The thermodynamic parameters were calculated from the temperature dependence of the equilibrium constants and are discussed. The synthesized metal chelates have been screened for their antimicrobial activities against the selected types of Gram-positive (G) and Gram-negative (G) bacteria. They were found to be more active against Gram positive than Gram negative bacteria. The antimicrobial activity in terms of metal ions obeys this order: Cu(II) > Ni(II) > Co(II). [ABSTRACT FROM AUTHOR]

Mononuclear cobalt(II), nickel(II), and copper(II) complexes of cetirizine·2HCl (CTZ = 2-[2-[4-[(4-chlorophenyl)phenyl methyl]piperazine-1-yl]-ethoxy]acetic acid) in the presence of alanine (Ala) as a representative example of amino acids were synthesized and elucidated by different physical techniques. All complexes have been characterized with the help of elemental analyses, molecular weights, molar conductance values, magnetic moments, and spectroscopic data. The measured molar conductance values in DMSO indicate that the complexes are nonelectrolytes. Quantum chemical calculations were performed with semi-empirical method to find the optimum geometry of complexes. The metal–oxygen bond length in the synthesized complexes obeys the order M–OH2 > M–OCTZ > M–OAla. Formation equilibria of the ternary complexes have been investigated. Ternary complexes are formed by a simultaneous mechanism. Stoichiometry and stability constants for the complexes formed are reported. The concentration distributions of various species formed in solution were also evaluated as a function of pH. CTZ and its metal chelates have been screened for their antimicrobial activities against some selected types of gram-positive (G+) and gram-negative (G−) bacteria. They were more active against (G+) than (G−) bacteria. The present article reports on the synthesis, characterization, and their electronic absorption spectra of M(II)–ternary complexes involving CTZ as antihistamine drug and alanine as a representative example of amino acids. The geometry of the studied M(II) complexes has been fully optimized using parameterized PM3 semi-empirical method. Protonation and complex formation equilibria were investigated. The antimicrobial activities were investigated. [ABSTRACT FROM PUBLISHER]