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The interaction of dibutyltin(IV) dichloride (DBT) with 1,4-diazacycloheptane (homopiperazine, HP) was investigated. In solutions, the complexes formed a 1:1 complex, its protonated and hydrolyzed forms. The formation constants of the complexes and thermodynamic parameters as ΔH° and ΔS° were estimated. The optimization of the structure of the (Bu)2Sn(HP)Cl2 complex reveals that the tin is six-coordinate in a distorted octahedral geometry, where the two nitrogen atoms of homopiperazine and the two chloride ions are in one plane. The solid (Bu)2Sn(HP)Cl2 complex with homopiperazine was synthesized, and the composition was assigned by elemental micro-analysis and mass spectrum. The complex was investigated by infrared, mass spectra, and thermal measurements. The ligand and its complex were tested against antimicrobial Staphylococcus aureus (+ve), Escherichia coli (−ve), and antifungal Candida albicans and Aspergillus flavus. Anticancer activities of homopiperazine and its dibutyltin(IV) complex were tested against breast cancer cell lines. The molecular docking investigations were performed to know the possible modes of binding to the most active sites of the breast cancer oxidoreductase receptor and those of Escherichia coli. [ABSTRACT FROM AUTHOR]

This review article presents an overview of the equilibrium studies on Pd-amine complexes with bio-relevant ligands in reference to their antitumor activity. Pd(II) complexes with amines of different functional groups, were synthesized and characterized in many studies. The complex formation equilibria of Pd(amine)2+ complexes with amino acids, peptides, dicarboxylic acids and DNA constituents, were extensively investigated. Such systems may be considered as one of the models for the possible reactions occurring with antitumor drugs in biological systems. The stability of the formed complexes depends on the structural parameters of the amines and the bio-relevant ligands. The evaluated speciation curves can help to provide a pictorial presentation of the reactions in solutions of different pH values. The stability data of complexes with sulfur donor ligands compared with those of DNA constituents, can reveal information regarding the deactivation caused by sulfur donors. The formation equilibria of binuclear complexes of Pd(II) with DNA constituents was investigated to support the biological significance of this class of complexes. Most of the Pd(amine)2+ complexes investigated were studied in a low dielectric constant medium, resembling that of a biological medium. Investigations of the thermodynamic parameters reveal that the formation of the Pd(amine)2+ complex species is exothermic. [ABSTRACT FROM AUTHOR]

The dimethyltin(IV) complex with 1,4‐dizacycloheptane (homopiperazine) was synthesized. The complex is of 1:1 stoichiometry. The complex was characterized by elemental analysis, spectroscopic techniques as infrared (IR) and nuclear magnetic resonance (NMR), and thermal measurements. Homopiperazine coordinates to dimethyltin(IV) by the two nitrogen atoms. The complex decomposes in two steps. The kinetic parameters of thermal decomposition process have been calculated using Coats–Redfern and Horowitz–Metzger methods. The high values of the energy of activation of the complexes reveal the high stability of the complex due to their covalent bond character. The two decomposition steps are endothermic. Density Functional Theory (DFT) calculations have been carried out to investigate the equilibrium geometry of homopiperazine and its complex. The calculated total energies, energies of highest occupied molecular orbital (HOMO), energies of lowest unoccupied molecular orbital (LUMO), and dipole moments are reported. Antibacterial, antifungal, and anticancer activities of homopiperazine and its dimethyltin(IV) complex were tested. The molecular docking studies were performed to find the possible binding modes to the most active sites of the receptor of breast cancer oxidoreductase and those of Escherichia coli. [ABSTRACT FROM AUTHOR]

The reaction of dimethyltin(IV) dichloride (DMT) with homopiperazine (HPIP) was studied. The equilibria of the complexes formed in solution were investigated. The complexes detected are of 1:1 stoichiometry in addition to the protonated and hydrolysed species. The complex formation constants were determined by the use of potentiometric technique and the non-linear computer program Miniquad-75. The dielectric constant effect of the reaction medium on the formation of the complexes was investigated. Formation constants of the complexes were determined at different temperatures and the thermodynamic parameters as ΔH° and ΔS° were estimated and discussed. The ternary complexes of dimethyltin(IV) with HPIP and DNA constituents are formed by a simultaneous mechanism. Their formation constants were determined. The speciation diagrams of the binary and mixed-ligand complexes were evaluated. [ABSTRACT FROM AUTHOR]

[Pd(BHEP)Cl2] and [Pd(BHEP)(CBDA)] complexes, where BHEP = 1,4-bis(2-hydroxyethyl)piperazine and CBDA = cyclobutanedicarboxylate, were synthesized and characterized. [Pd(BHEP) (CBDA)] crystallizes in space group P21, a = 9.5740(8) Å, b = 9.4700(7) Å, c = 9.7890(10) Å, α = 90.00°, β = 113.360(5)°, γ = 90.00°, V = 814.78(13) Å3, Z = 2. The palladium center has a typical square planar geometry with tetrahedral distortion. DFT calculations show good agreement between theoretical and X-ray data. The stability constants and stoichiometry of the complexes formed between various dicarboxylic acids and [Pd(BHEP)(H2O)2]2+ were studied. Dicarboxylic acids form 1:1 and protonated complexes. Inosine forms 1:1, 1:2 and the protonated form of 1:1 complexes. The temperature effect on the formation constant of the cyclobutanedicarboxylate complex was investigated. The hydrolysis of [Pd(BHEP)(H2O)2]2+ and complex formation with cyclobutanedicarboxylic acid are exothermic processes. [ABSTRACT FROM AUTHOR]

Proton-ligand association constants of 1-benzoyl(1,2,4-triazol-3-yl)thiourea (BTTU) and its complex formation constants with some bivalent metal ions Ni(II), Co(II), Mn(II), Zn(II), and Cu(II), have been determined potentiometrically in 50% EtOH–H2O and 0.1 M NaNO3. The complexes formed in solution have a stoichiometry of 1:1 and 1:2 [M:L], where M represents the metal ion and L the BTTU ligand. The corresponding thermodynamic parameters are derived and discussed. The complexes are stabilized by enthalpy changes and the results suggest that complexation is an enthalpy-driven process. The effects of metal ion, ionic radius, electronegativity, and nature of ligand on the formation constants are discussed. The formation constants of the complexes with 3d transition metals follow the order Mn2+ < Co2+ < Ni2+ < Cu2+ > Zn2+. The metal complexes were synthesized and characterized by elemental analyses, conductance, IR,1H NMR, and magnetic measurements. The low magnetic moment of 0.11 BM for the Cu(II) complex is suggestive of dimerization through Cu–Cu interaction. The concentration distribution diagrams of the complexes were evaluated. The ligands and their metal complexes have been screenedin vitroagainst some bacteria and fungi. [ABSTRACT FROM AUTHOR]

The [Pd(AEMP)Cl2] complex [AEMP = 2-(2-aminoethyl)-1-methylpyrrolidine] was prepared and characterized by single-crystal X-ray diffraction and spectroscopic analyses. The structure of the complex was found to be square-planar with some distortion. The geometric optimizations of the ligand and complex were performed with the DFT/B3LYP method by using Gaussian 09. The stoichiometry and stability constants of the complexes formed in the reaction of [Pd(AEMP)(H2O)2]2+ with dicarboxylic acids and DNA constituents were investigated at 0.1 m ionic strength and 25 °C. The results show that both DNA constituents and cyclobutanedicarboxylate (CBDCA) coordinate to [Pd(AEMP)(H2O)2]2+ to form the quaternary complex [Pd(AEMP)(CBDCA-O)DNA], where CBDCA-O represents cyclobutanedicarboxylate coordinated through one carboxylate oxygen atom to the PdII center. The speciation concentration distributions in solution were evaluated. The biological activity for DNA cleavage and cytotoxicity of the [Pd(AEMP)Cl2] complex was studied. [ABSTRACT FROM AUTHOR]

Amino acid esters (L) react with [Pd(Eten)(H 2 O) 2 ] 2+ (Eten = N -ethyl ethylenediamine) giving mixed ligand complexes of the type [Pd(Eten)L] 2+ . Base hydrolysis of [Pd(Eten)L] 2+ was studied by pH-stat technique from which rate constants for the base hydrolysis of the esters were obtained. The glycine methyl ester hydrolysed significantly, whereas the methionine methyl and histidine methyl esters hydrolysed much slower. The mode of coordination of the ester plays a role in the catalysis, and possible mechanisms for these reactions are considered. Activation parameters were determined for the hydrolysis of the glycine methyl ester. The effect of the dielectric constant of the medium on the hydrolysis process was also investigated. The B3LYP/LANL2DZ method was used for geometric optimization of the free ligand and the complex using the Gaussian 09 program. The calculations are compared with the kinetic data. In addition, the vibrational frequencies of the molecules were computed for the optimized geometries. [ABSTRACT FROM AUTHOR]

[Pd(BHEP)Cl2] (BHEp = 1,4-bis(2-hydroxyethyl)piperazine) was synthesized and characterized. The palladium center has a typical square-planar geometry with a tetrahedral distortion. The alcohol groups of the ligand do not participate in binding to Pd(II). The DFT/B3LYP method was used for geometric optimization of the ligand and the complex using the Gaussian 09 program and compared with experimental results. The stoichiometry and stability constants of the complexes formed between [Pd(BHEP)(H2O)2]2+and some selected amino acids, peptides, and DNA constituents were investigated at 25 °C and 0.1 M ionic strength. The binuclear complex [(H2O)(BHEP)Pd(Bip)Pd(BHEP)(H2O)]4+was detected, where Bip = 4,4′-bipiperidine. Inosine, uracil, and thymine interact with the binuclear complex via substitution of both coordinated water molecules. The potentiometric results were complimented by spectroscopic measurements. The concentration distribution diagrams of the various species formed were evaluated. [ABSTRACT FROM AUTHOR]

Pd(BHEP)Cl2was synthesized and characterized (BHEP = 1,4-bis(2-hydroxyethyl)piperazine). The complex decomposes in two steps, leaving a residue of palladium metal. Amino acid ester (L) reacts with [Pd(BHEP)(H2O)2]2+(BHEP = 1,4-bis(2-hydroxyethyl)piperazine), giving mixed-ligand complexes, [Pd(BHEP)L]2+. The kinetics of hydrolysis of [Pd(BHEP)L]2+have been studied by pH-stat technique, and rate constants were obtained. Rate acceleration observed for glycine methyl ester is high. The effect with methionine methyl ester is much less marked, as the mixed-ligand complexes with these ligands do not involve alkoxycarbonyl donors. Possible mechanisms for these reactions are considered. The thermal stability of Pd(BHEP)Cl2complex was investigated. The role of the complex in the catalysis of amino acid esters was studied. [ABSTRACT FROM AUTHOR]

Pd(MME)Cl2complex, where MME = methionine methyl ester, was synthesized and characterized by elemental analysis and spectroscopic techniques. [Pd(MME)(H2O)2]2+interacts with some DNA constituents giving 1 : 1 and 1 : 2 complexes. The binuclear complexes having 4,4′-bipiperidine as a linker and involving [Pd(MME)(H2O)2]2+and DNA constituents were investigated. The results show formation of [(H2O)(MME)Pd(Bip)Pd(MME)(H2O)]4+. Inosine, uracil, and thymine interact with the previously mentioned complex by substitution of the two coordinated water molecules. Formation constants of all possible mono- and binuclear complexes were determined and their speciation diagrams were evaluated. Electronic spectra of [Pd(MME) (H2O)2]2+and its uracil complexes Speciation of mono- and binuclear Pd(II) complexes involving mixed nitrogen–sulfur donor ligand is investigated; 4,4′-bipiperidine is used as a linker. [ABSTRACT FROM AUTHOR]

The complex formation equilibria in the reaction of [Pd(en)(H2O)2]2+with 4,4′-bipiperidine (Bip) and DNA constituents such as inosine, inosine-5′-monophosphate, uracil, uridine, thymine, and thymidine were investigated at 25 °C and 0.1 M ionic strength. The [(H2O)(en)Pd(Bip)Pd(en)(H2O)]4+complex and its hydrolyzed species were formed. Substitution of coordinated water by inosine (Ino) as DNA constituent formed the complexes [(Ino)(en)Pd(Bip)Pd(en)(H2O)]3+and [(Ino)(en)Pd(Bip)Pd(en)(Ino)]2+. The formation of the binuclear complexes was further supported by spectral measurements. The formation constants of all possible mono- and binuclear complexes were determined and their speciation diagrams were evaluated. Binuclear complexes involving 4,4′-bipiperidine linkage of two Pd(en)2+species were investigated. The binding of DNA constituents to the binuclear complex was studied. [ABSTRACT FROM AUTHOR]

Highlights: [•] The Cu(II) complex involving bio-relevant ligands was investigated. [•] The manuscript is in the domain of SAA as it deals with spectral and potentiometric study. [•] The activation of amino acid ester hydrolysis was studied. [•] The results is expected to contribute to the chemistry of plant hormone. [Copyright &y& Elsevier]

The review is mainly concerned with the protonation equilibria of biologically active ligands like amino acids, peptides, DNA constituents, and amino acid esters in nonaqueous media. Equilibrium concentrations of proton-ligand formation as a function of pH were investigated. Also, thermodynamics associated with protonation equilibria were also discussed. [ABSTRACT FROM AUTHOR]

Pd(MME)Cl2 complex (MME = methionine methyl ester) was synthesised and characterized by physicochemical measurements. The reaction of [Pd(MME)(H2O)2]2+ with amino acids, peptides, or dicarboxylic acids was investigated at 25°C and 0.1M ionic strength. Amino acids and dicarboxylic acids form 1 : 1 complexes. Peptides form both 1 : 1 complexes and the corresponding deprotonated amide species. The stability of the complexes formed was determined and the binding centres of the ligands were assigned. Effect of solvent on the stability constant of Pd(MME)-CBDCA complex, taken as a representative example, shows that the complex is more favoured in a medium of low dielectric constant. The concentration distribution diagrams of the complexes were evaluated. [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]

Abstract: 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, 1H 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 0.1M NaNO3 at different temperatures and the corresponding thermodynamic parameters were derived and discussed. The order of −ΔG° and −ΔH° were found to obey Mn2+

Abstract: The synthesis and X-ray structural characterization of Pd(DMPA)Cl2 complex, where DMPA= N,N-dimethylaminopropylamine, is reported. The complex crystallizes in the space group P21/c, a =8.8923(4), b =10.9050(5), c =11.5006(7) Å, β =120.00(18)°, V =948.25(8) Å3, Z =4. The palladium centre has a typical square-planar geometry with a tetrahedral distortion. Stoichiometry and stability constants of the complexes formed between [Pd(DMPA)(H2O)2]2+ and some selected DNA constituents and cytsteine are investigated at 25°C and at constant 0.1M ionic strength. The concentration distribution diagrams of the various species formed are evaluated. The equilibrium constants for the displacement of coordinated ligands as inosine by cysteine are calculated. The results are expected to contribute to the chemistry of tumour therapy. [Copyright &y& Elsevier]

Abstract: Pd(dmen)Cl2 complex was synthesized and characterized, where dmen=N,N-dimethylethylenediamine. Stoichiometry and stability constants of the complexes formed between [Pd(dmen)(H2O)2]2+ and various biologically relevant ligands such as amino acids, peptides and dicarboxylic acids are investigated at 25°C and at constant 0.1M ionic strength. The concentration distribution diagrams of the various species formed are evaluated. The equilibrium constants for the displacement of coordinated ligands as inosine, glycine or methionine by cysteine are calculated. The results are expected to contribute to the chemistry of tumour therapy. [Copyright &y& Elsevier]

Abstract: Pd(DHP)Cl2 and Pd(DHP)(CBDCA) complexes (DHP=1,3-diamino-2-hydroxopropane and CBDCA=1,1-cyclobutanedicarboxylate), were synthesized and characterized by elemental analysis, IR and NMR spectral measurements. The coordination of [Pd(DHP)(H2O)2]2+ with some selected bio-relevant ligands, containing different functional groups was investigated. The ligands used are amino acids, peptides, DNA constituents and dicarboxylic acids. Stoichiometry and stability constants of the complexes formed are reported at 25°C and 0.1M ionic strength. The results show the formation of 1:1 complexes with amino acids and dicarboxylic acids. DNA constituents form 1:1 and 1:2 complexes. Peptides form both 1:1 complexes and the corresponding deprotonated amide species. The effect of chloride ion concentration and dioxane on the acid dissociation constants of 1,1-cyclobutane dicarboxylic acid (CBDCAH2) and the formation constant of its complex with Pd(DHP)2+ was reported. The equilibrium constants for the displacement of coordinated ligands as uracil, glycine or methionine by cysteine are calculated. The results are expected to contribute to the chemistry of antitumour agents. [Copyright &y& Elsevier]

Abstract: Pd(deen)Cl2 and Pd(deen)(CBDCA) complexes, where deen= N,N-diethylethylenediamine and CBDCA=1,1-cyclobutanedicarboxylate, were synthesized and characterized by elemental analysis and spectroscopic techniques. The stoichiometry and stability of the complexes formed between various biologically relevant ligands (amino acids, peptides, DNA constituents and dicarboxylic acids) and [Pd(deen)(H2O)2]2+ were investigated at 25°C and 0.1M ionic strength. The speciation diagrams of the complexes formed in solutions are evaluated. The mode of coordination of glycylglycine is investigated by spectrophotometric measurements. The equilibrium constants for the displacement of coordinated ligands as inosine, glycine or methionine by mercaptoethylamine are calculated. The results are expected to contribute to the chemistry of antitumour agents. [Copyright &y& Elsevier]

The hydrolysis of amino acid esters is catalysed by the palladium(II) complex [Pd(Pic)]2+ (Pic = 2-picolylamine). The reaction has been studied by the pH-stat technique. The overall PdII chelate-promoted hydrolysis of the ethyl esters of glycine and alanine may be accounted by inter- and intramolecular mechanisms depicted in Eqns (1) and (2) respectively. [Pd(Pic)(NH2CH(R)CO2R]2+ + OH- k1→[Pd(Pic)(NH2CH(R)CO2]+ + ROH (1) [Pd(Pic)(NH2CH(R)CO2R(OH)]+ + k2→[Pd(Pic)(NH2CH(R)CO2)] + ROH (2) The kinetic data for histidine and methionine methyl esters are fitted assuming that hydrolysis proceeds solely by the intermolecular mechanism [Eqn (1)]. The rate enhancement compared with the free ester is discussed in terms of the structure of the complex. Activation parameters associated with the hydrolysis have been determined and discussed. [ABSTRACT FROM AUTHOR]

Pd(DME)Cl2 complex was synthesized and characterized, where DME is 2-{[2-(dimethylamino)ethyl]-methylamino}ethanol. Stoichiometry and stability constants of the complexes formed between various biologically relevant ligands (amino acids, peptides, DNA constituents, and dicarboxylic acids) and [Pd(DME)(H2O)2]2+ are investigated at 25°C and at constant 0.1 M ionic strength. The effect of dielectric constant of the medium on the stability constant of Pd(DME)-CBDCA complex, where CBDCA is cyclobutanedicarboxylate, is also reported. The concentration distribution diagrams of the various species formed are evaluated. The kinetics of base hydrolysis of amino acid esters coordinated to Pd(DME)2+ complex is investigated. The effect of the temperature on the kinetics of base hydrolysis of glycine methyl ester complex is studied. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 608–618, 2010 [ABSTRACT FROM AUTHOR]

The kinetics of base hydrolysis of amino acid esters, glycine-, histidine-, and methionine methyl esters in the presence of [Pd(Et4en))(H2O)2]2+ is studied in aqueous solution at 25°C and I = 0.1 mol dm-1 (Et4en = N,N,N',N'-tetraethylethylenediamine). The rate of ester hydrolysis for glycine methyl ester is studied at different temperatures and dioxane-water solutions of different compositions. The kinetic data fit a model which assumes that hydrolysis proceeds in one step. Hydrolysis of the esters is catalyzed by [Pd(Et4en)(H2O)2]2+ with catalysis ratio values of 2.5 × 104, 3.15, and 7.43 for glycine-, histidine-, and methionine methyl esters, respectively. Activation parameters for the base hydrolysis are evaluated. [ABSTRACT FROM AUTHOR]

Abstract: In the present study, a new ligand is prepared by condensation of hydralazine (1-Hydralazinophthalazine) with 2-butanon-3-oxime. The acid-base equilibria of the schiff-base and the complex formation equilibria with the metal ions as Cu(II), Ni(II), Co(II), Cd(II), Mn(II) and Zn(II) are investigated potentiometrically. The stability constants of the complexes are determined and the concentration distribution diagrams of the complexes are evaluated. The effect of metal ion properties as atomic number, ionic radius, electronegativity and ionization potential are investigated. The isolated solid complexes are characterized by conventional chemical and physical methods. The potential coordination sites are assigned using the i.r. and 1H NMR spectra. The structures of the isolated solid complexes are proposed on the basis of the spectral and magnetic studies. [Copyright &y& Elsevier]

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]

Abstract: Formation equilibria of copper(II) complexes of 2-(aminomethyl)-benzimidazole (AMBI) and the ternary complexes Cu(AMBI)L (L=amino acid, amide, dicarboxylic acid 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(AMBI)L, whereas amides form two complex species Cu(AMBI)L and Cu(AMBI)(LH−1). The ternary complexes of copper(II) with AMBI and dicarboxylic acids or DNA units are formed by a stepwise mechanism, whereby binding of copper(II) to AMBI is followed by ligation of the dicarboxylic acids or DNA components. The values of Δ log K indicate that the ternary complexes containing aromatic amino acids are significantly more stable than the complexes containing alkyl- and hydroxyalkyl-substituted amino acids. This may be taken as an evidence for a stacking interaction between the aromatic moiety of AMBI and the aromatic side chains of the bio-active ligands. The solid complexes Cu(AMBI)L where L=1,1-cyclobutanedicarboxylic acid (CBDCA) and malonic acid were separated and identified by elemental analysis and infrared spectroscopy and magnetic moment. The decomposition course and steps for the isolated complexes were analyzed and the kinetic parameters of the non-isothermal decomposition were calculated. The hydrolysis of glycine methyl ester (MeGly) is catalyzed by the Cu(AMBI)2+ complex. The kinetic data is fitted assuming that the hydrolysis reaction 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 OH− ion. The second step involves the equilibrium formation of the hydroxo-complex Cu(AMBI)(MeGly)(OH) followed by intramolecular OH− attack. [Copyright &y& Elsevier]

The complex formation reactions of [Cu(NTP)(OH 2 )] 4- (NTP&ThickSpace;=&ThickSpace;nitrilo-tris(methyl phosphonic acid)) with some selected bio-relevant ligands containing different functional groups, are investigated. Stoichiometry and stability constants for the complexes formed are reported. The results show that the ternary complexes are formed in a stepwise mechanism whereby NTP binds to copper(II), followed by coordination of amino acid, peptide or DNA. Copper(II) is found to form Cu(NTP)H n species with n &ThickSpace;=&ThickSpace;0, 1, 2 or 3. The concentration distribution of the various complex species has been evaluated. The kinetics of base hydrolysis of glycine methyl ester in the presence of copper(II)-NTP complex is studied in aqueous solution at different temperatures. It is proposed that the catalysis of GlyOMe ester occurs by attack of OH - ion on the uncoordinated carbonyl carbon atom of the ester group. Activation parameters for the base hydrolysis of the complex [Cu(NTP)NH 2 CH 2 CO 2 Me] 4- are, ΔH ± &ThickSpace;=&ThickSpace;9.5&ThickSpace;±&ThickSpace;0.3&ThickSpace;kJ&ThickSpace;mol -1 and ΔS ± &ThickSpace;=&ThickSpace;-179.3&ThickSpace;±&ThickSpace;0.9&ThickSpace;J&ThickSpace;K -1 &ThickSpace;mol -1 . These show that catalysis is due to a substantial lowering of ΔH ± . [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Mixed-ligand complex formation equilibria of Pd(Me2en)–CBDCA–DNA constituent have been investigated (Me2en=N,N′-dimethylethylenediamine, CBDCA=cyclobutane dicarboxylic acid). The results show ring opening of CBDCA and monodentate complexation of the DNA constituent. Stoichiometries and stability constants of the complexes were determined at 25 °C and at constant 0.1 M ionic strength. The kinetics of base hydrolysis of glycine methyl ester in presence of Pd(Me2en)2+ complex was studied in aqueous solution at different temperatures, and in dioxane–water solutions of different compositions at 25 °C. [Copyright &y& Elsevier]

Acid-base equilibria of the iron(III) complexes of Schiff base synthesized from 2,6-diacetylpyridine and amino alcohol as, glucosamine or ethanolamine were investigated. These complexes are abbreviated as [Fe(dapGH 2)(H 2 O) 2 ]3+ and [Fe(dapEH 2)(H 2 O) 2 ]3+ for glucosamine and ethanolamine respectively. The pKa for induce ionization of the alcohol hydrogen atoms and the coordinated water molecules were also determined. The hepta-coordination mode of Fe(III) ion is evidenced by the hydrolysis data. The equilibrium constants were measured by potentiometric titration at 25 °C and ionic strength 0.1 M NaNO 3 using the non linear least-squares program MINIQUAD-75. The speciations of the various complex species were obtained as a function of pH. DFT calculations were carried out for Schiff base that derived from ethanolamine (dapEH 2) and its ferric complex. Molecular docking studies have proved that dapEH 2 and [Fe(dapEH 2)(H 2 O) 2 ]3+ interact with ribosyltransferase (code: 3GEY) through the amino acids active sites. All suggested ligands and their ferric complexes were screened in vitro against some selected bacteria. The antioxidant properties of the ferric complexes were examined by the DPPH test. [Fe(dapEH 2)(H 2 O) 2 ]3+ showed higher antioxidant activity than the [Fe(dapGH 2)(H 2 O) 2 ]3+. The IC 50 values of [Fe(dapEH 2)(H 2 O) 2 ]3+ complex and [Fe(dapGH 2)(H 2 O) 2 ]3+ complex were found to be 160.18 and 394.3 µg/ml respectively. [ABSTRACT FROM AUTHOR]

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]

The newly synthesized Schiff base‐oxime ligand, namely, (2Z,3E)‐3‐((3‐(4‐(3‐(((2E,3E)‐3‐(hydroxyimino)butan‐2‐ylidene)amino)propyl)piperazin‐1‐yl)propyl)imino)butan‐2‐one oxime (H2L) and its Co (II), Cu (II), and Zn (II) complexes were reported. The characterization was accomplished with the aid of CHN‐EA, mass, fourier transform infrared spectroscopy (FT‐IR), electronic spectra, magnetic moment, molar conductance and TGA. According to the spectroscopic approaches, the synthesized ligand (H2L) may act as a tetradentate or hexadentate (bis‐tridentate) coordinating ligand through the azomethine nitrogen, piperazinyl nitrogens, and oximato‐nitrogens affording distorted square planar mononuclear Co (II) complex or tetrahedrally distorted square planar binuclear Cu (II) and Zn (II) complexes whereas the coordination mode varies according to the nature of the metal ion. The microbial resistance of all the synthesized compounds was evaluated and reported. Findings showed that the Cu (II) complex has mostly the highest inhibitory effects against all tested microbial strains. Besides, the anticancer nature of the studied compounds was also evaluated against a panel of three different human cancer cells, including (HCT‐116), (MDA‐MB‐231), (HepG2) in addition to the (WI‐38) used as a healthy cells. In general, the Cu (II) complex displayed the best cytotoxic profiles against the tested cells than the Co (II) and Zn (II) complexes with negligible toxicity towards the (WI‐38) normal cells. The DNA cleavage activities of all tested compounds were assayed against pBR322 plasmid DNA. Whereas, the Cu (II) complex showed the highest DNA cleavage propensity, which proceeds predominantly via the oxidative mechanism. Additionally, flow cytometric analysis dictates that the Cu (II) complex induces cell cycle arrest in S‐phase and apoptotic cell death on HCT‐116 cells. The morphological transformations distinguished in HCT‐116 cells treated with Cu (II) complex have been depicted with the aid of scanning electron microscopy (SEM). The docking results indicate that the Cu (II) complex strongly interacts with human colon cancer (6GUE), Escherichia coli (3T88), Klebsiella pneumoniae (4HL2), and Staphylococcus aureus (3WQU) proteins, through different modes of interactions that harmonize successfully with the experimental results. [ABSTRACT FROM AUTHOR]

Herein, we report the synthesis and biological evaluation of [Pd(L)(OH 2)Cl] complex (where L = 2,2′-(pyridin-2-ylmethylene)bis(5,5-dimethylcyclohexane-1,3-dione) as a novel promising anticancer candidate. The complex was characterized by single-crystal X-ray diffraction and other various spectroscopic techniques. Besides, the optimized structure was determined through DFT calculations revealing that the coordination geometry of [Pd(L)(OH 2)Cl] complex is square planar. The binding propensity of [Pd(L)(OH 2)Cl] complex with DNA and BSA was assessed by the spectrophotometric method. The antimicrobial profile of the ligand and its [Pd(L)(OH 2)Cl] complex was screened against clinically important bacterial strains. [Pd(L)(OH 2)Cl] complex showed promising activity against these microorganisms. Pd(L)(OH 2)Cl] complex exhibited a potent antiproliferative potential compared to its ligand against different human cancer cells (A549, HCT116, MDA-MB-231, and HepG2) with less toxic effect against normal cells (WI-38). Additionally, [ Pd(L)(OH 2)Cl] complex exerted its anticancer effects against the most responsive cells (HCT116 cells; IC 50 = 11 ± 1 μM) through suppressing their colony-forming capabilities and triggering apoptosis and cell cycle arrest at S phase. Quantitative PCR analysis revealed a remarkable upregulation of the mRNA expression level of p53 and caspase-3 by 4.8- and 5.9-fold, respectively, relative to control. Remarkable binding properties and non-covalent interactions between L and its [Pd(L)(OH 2)Cl] complex with the binding sites of different receptors including CDK2, MurE ligase, DNA, and BSA were established using molecular docking. Based on our results, [Pd(L)(OH 2)Cl] complex is an intriguing candidate for future investigations as a potential anticancer drug for the treatment of colon cancer. [Pd(L)(OH 2)Cl] complex was synthesized and characterized by X-ray crystallography. [Pd(L)(OH 2)Cl] complex binding potentials towards different receptors were evaluated using docking. Anticancer activity was evaluated using MTT, apoptotic, and cell cycle assays. Caspase-3 and p53 expression levels were upregulated by 4.8- and 5.9-fold compared to control cells using qRT-PCR analysis. [Display omitted] • A new palladium complex was synthesized and confirmed through X-ray investigation. • [Pd(L)(OH 2)Cl] complex showed good antibacterial effects and DNA/BSA-binding potentials. • The complex revealed a potent cytotoxicity against different human cancer cells. • Caspase-3 and p53 expression levels were significantly upregulated using qPCR analysis. • Docking showed binding properties of [Pd(L)(OH 2)Cl] complex towards different receptors. [ABSTRACT FROM AUTHOR]

The interaction of dimethyltin(IV) dichloride (DMT) with 1,4-piperazine (PIP) was investigated. The complex formation equilibria of the complexes formed in solution were investigated. The stoichiometry and stability constants of the complexes formed in solution phase were determined at different temperatures and in solutions of dioxane–water mixtures of different dielectric constants. The equilibrium constant for the displacement of piperazine coordinated to dimethyltin(IV) by inosine as a representative of DNA was calculated. (DMT)(PIP)·3H2O was synthesized and characterized by elemental analysis, spectral, and thermal techniques. The antitumor activity of the complex was screened. [ABSTRACT FROM PUBLISHER]

Abstract: 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]·nH2O, 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 nitrogen’s, 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 Cu2+, Co2+ and Ni2+ complexes were determined by potentiometric titration method in 50% DMSO–water solution at ionic strength of 0.1M sodium nitrate. It has been observed that the protonated Schiff base ligand (BHPP) have four protonation constants. The divalent metal ions Cu2+, Ni2+ and Co2+ form 1:1 complexes. [Copyright &y& Elsevier]

Thermodynamic parameters for protonation of 1,4-bis(3-aminopropyl)-piperazine (BAPP) and itsmetal complexation with some divalent metal ions were determined in aqueous solution at constant ionic strength (0.1M 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. [ABSTRACT FROM AUTHOR]

The kinetics of base hydrolysis of glycine-, histidine-, and methionine methyl esters in the presence of [Cu-Me4en]2+ complex is studied in aqueous solutions and in dioxane–water solutions of different compositions at T = 25°C and I = 0.1 mol dm-1. The kinetics of base hydrolysis of glycine and methionine methyl esters is studied at different temperatures. The kinetic data fits assuming that the hydrolysis proceeds in one step. The activation parameters for the base hydrolysis of the complexes are evaluated. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 737–745, 2006 [ABSTRACT FROM AUTHOR]

Complex-formation equilibria involvingtrans-diamine palladium(II) (PdII), 4,4?-bipyridine (bpy), and inosine were investigated at 25?°C and 0.1?M (NaNO3) ionic strength. The stability constants of all possible mono-nuclear and binuclear complexes were determined. The concentration distribution diagram for the binuclear complexes of PdII-bpy-inosine reveals the complexes that predominate in the physiological pH range and the quite feasible interaction of the binuclear complex PdII-bpy-PdIIwith inosine as a DNA constituent. On the basis of DFT calculations (B3LYP/LANL2DZp), the structures of the investigated equilibrium species show typical bond lengths for Pd–O and Pd–N bonds. The C–C bond in [Pd(4,4?-bpy)(NH3)2(OH2)]2+is clearly shortened to 1.47?Å, leading to reduced aromaticity in bpy. Comparison with model compounds suggests that the uncoordinated aromatic ring can be understood as an electron donating group. [ABSTRACT FROM AUTHOR]