Concentration Distribution Diagrams Research Articles

Amine-bridged binuclear palladium(II) complexes with inosine. Equilibrium studies and DFT calculations

Complex-formation equilibria involving trans-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-PdII with 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.

Kinetics, mechanism, and equilibrium studies of the reactions between a ruthenium(II) complex and some nitrogen- and sulfur-donor nucleophiles

Kinetics and mechanism of the substitution reactions between [Ru(trpy)(bpy)Cl]+ with nucleophiles guanosine-5′-monophosphate, l-histidine, thiourea, and dimethylsulfoxide were studied spectrophotometrically in 0.1 M NaClO4 at 310 K. The observed order of reactivity for selected ligands is: thiourea > guanosine-5′-monophosphate > l-histidine > DMSO. This order is associated with the electronic, structural, and chemical characteristics of complex and nucleophiles. The substitution reaction with thiourea was studied at three different temperatures (288, 298, and 310 K). Negative entropy of activation ΔS ≠ confirms the associative mode of activation. The complex formation of [Ru(trpy)(bpy)H2O]2+ with ligands guanosine-5′-monophosphate and l-histidine was investigated by potentiometry and spectrophotometry as well. The stoichiometry and stability constants of the species formed in these systems were determined. The concentration distribution diagram of the various complexes has been evaluated as a function of pH. Comparing the calculated values for logβ, we determined that the product with nucleotide is more stable than the product with l-histidine.

Configurational, LFDFT and NBO analysis of chromium(III) complexes of edta-type ligands

A new hexadentate chromium(III) complex, Na[Cr(l,3-pd3ap)]·3H2O, containing an unsymmetrical edta-type ligand, the 1,3-propanediamine-N,N,N′-triacetate-N′-3-propionate ion (1,3-pd3ap), has been prepared, chromatographically separated and characterized. Only one [trans(O5)] of the two possible geometrical isomers was isolated. In this isomer the two five-membered glycinate rings (R rings) occupy trans-axial sites, while the one glycinate ring and one β-alaninate ring lie in the equatorial plane with the two diamine nitrogens (G rings). This result confirms the assignment made on the basis of Density Functional Theory (DFT), IR and UV–Vis spectral data analyses. The spectral data and electronic transition assignment, DFT–NBO, Ligand Field DFT and extensive strain analysis are discussed by a comparison with those of other [Cr(edta-type)]− complexes of known configurations. The stoichiometry and stability of the complexes formed between the chromium(III) ion and 1,3-propanediamine-N,N,N′-triacetic-N′-propionic acid (H41,3-pd3ap) were determined in aqueous solution by potentiometry at 25°C and 0.1M NaCl ionic strength. The existence of Cr(HnL), n=0, 1, 2 and 3 type complexes were verified. The formation of the Cr(OH)L complex was observed at higher pH values. The concentration distribution diagrams of the complexes were evaluated.

Complex formation reactions and equilibrium studies of mixed ligand complexes of diaqua (1-Phenyl piperazine)(Palladium)(II) with some biologically relevant ligands.

With the purpose of the search of new antitumor metal complexes, the complex-formation reactions of [Pd(Phenpip)(H2O)2] 2+ (Phenpip = 1-Phenylpiperazine) with some selected bio-relevant ligands, containing different functional groups (amino acids, peptides, DNA constituents and dicarboxylic acids) 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, inosine 5´-monophosphate (5-IMP) form only 1 : 1 complexes. The stability constant of the complexes formed in solution were determined and the binding centers of the ligands were assigned. The concentration distribution diagrams of the complexes were evaluated

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, 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+<Co2+<Ni2+<Cu2+, 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.

Synthesis and structural characterization of Pd(N,N-dimethylaminopropylamine)Cl2 complex – The interaction with bio-relevant ligands with reference to the effect of cysteine on the deactivation of metal-based drug

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.

Thermodynamics of the interaction of Pd(dmen)(H2O)22+ with bio-relevant ligands with reference to the deactivation of metal-based drug by thiol ligands

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.

Coordination properties of N,O-carboxymethyl chitosan (NOCC). Synthesis and equilibrium studies of some metal ion complexes. Ternary complexes involving Cu(II) with (NOCC) and some biorelevant ligand

Abstract In the present study, the acid-base equilibria of N,O-carboxymethy chitosan abbreviated as (NOCC), is investigated. The complex formation equilibria with the metal ions Cu(II), Ni(II), Co(II), Mn(II), and Zn(II) are investigated potentiometrically. The stability constant values of the binary and ternary complexes formed in solution were determined and the binding centers of the ligands were assigned. The relationships between the properties of the studied central metal ions as ionic radius, electronegativity, atomic number, and ionization potential, and the stability constants of the formed complexes were investigated in an effort to give information about the nature of chemical bonding in complexes and make possible the calculation of unknown stability constants. Cu(II), Ni(II), and U(VI) complexes with NOCC are isolated as solid complexes and characterized by conventional chemical and physical methods. The structures of the isolated solid complexes are proposed on the basis of the spectral and magnetic studies. The ternary copper(II) complexes involving NOCC and various biologically relevant ligands containing different functional groups, as amino acids and DNA constituents are investigated. The stability constants of the complexes are determined and the concentration distribution diagrams of the complexes are evaluated.

Thermodynamics of the reactions of [Pd(Et4en)(H2O)2]2+ with ligands of biological significance: deactivation of based-drug by the sulfur-containing biomolecules

The reaction of [Pd(Et4en)(H2O)2]2+ (Et4en=N,N,N′,N′-tetraethylethylenediamine) with amino acids, peptides, dicarboxylic acids or DNA constituents was investigated at 37°C and 0.16 M ionic strength. The stoichiometry and stability of the complexes formed were determined and the binding centers of the ligands were assigned. The concentration distribution diagrams of the complexes were evaluated. The equilibrium constants for the displacement of representative coordinated ligands such as inosine, glycine or methionine by mercaptoethylamine were calculated and the concentration distribution diagrams of the various species were evaluated. Pd(Et4En)Cl2 complex, where Et4En = N,N,N′,N′-tetraethylethylenediamine, was synthesized and characterized by elemental analysis and spectroscopic technique. The complex formation equilibria was investigated. The displacement of coordinated inosine (A) by cysteine (B) was studied. The equilibrium constant for the displacement reaction given is given by

Potentiometric studies of the interaction of amine-bridged dinuclear palladium(II) complex with nitrogen bases

Complexes formed by interaction of trans-diamminepalladium(II) chloride (PdII) with 1,6-hexanediamine (HDA) and nitrogen bases (B) (imidazole derivatives or methylamine) are investigated at 25°C and 0.1 mol L−1 NaNO3 ionic strength using potentiometric measurements. The stability constants of all possible mononuclear and binuclear complexes were determined. The concentration distribution diagram of the binuclear PdII-HDA-Im derivative reveals the complexes predominating in the physiological pH range; the reaction of the binuclear PdII-HDA-PdII with imidazole derivatives is quite feasible.

Equilibrium and kinetic investigation of the interaction of model palladium(II) complex with biorelevant ligands

AbstractPd(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

Spectrophotometric determination of acidity constants of 4-(2′–thiazolylazo)- resorcinol (TAR) in water–organic mixtures

The acidity constants of TAR in different water–organic solvent binary mixtures at 25 °C have been determined spectrophotometrically. DATa ANalysis (DATAN) program was used for calculations of the acidity constants and pure spectra of all formed species and their concentration distribution diagram in applied pH interval. Results show that there are a fairly inverse relationship between acidity constants and the mole fraction of the organic solvent in the binary mixtures. Effects of solvent composition on the p K as and pure spectrum of each component are also discussed.

Complex formation reactions between [Pd(piperazine)(H2O)2]2+ and biorelevant ligands: synthesis and equilibrium constants

[Pd(pip)Cl2], [Pd(pip)(cbdca)] ⋅ 2H2O, and [Pd(pip)(malonate)] ⋅ 2H2O complexes were synthesized and characterized, where pip is piperazine and cbdca is cyclobutanedicarboxylate. The stoichiometry and stability of the complexes formed between [Pd(pip)(H2O)2]2+ and various biologically relevant ligands (amino acids, peptides, DNA constituents, and dicarboxylic acids) were investigated at 25°C and 0.1 M ionic strength. The stability constant of the complexes formed in solution was determined and the binding centers of the ligands were assigned. The concentration distribution diagrams of the complexes were evaluated.

Chemometric 방법에 의한 메탄올/물 계에서 전이 금속 이온과 소염제 Piroxicam의 산성도 및 착체 형성에 관한 분광광도법 연구

소염제 piroxicam (PX, 4-hydroxy-2-methyl-N-2-pridyl-2H-1, 2-benzothiazine-3-carboxadiamide-1,1-dioxide)의 착물형성을 전이금속이온, Co(II), Ni(II), Cu(II), Zn(II)과 함께 메탄올(MeOH)/물 이성분 혼합물에서 25<TEX>$^{\circ}C$</TEX>, 일정한 pH=5.0와 I=0.1 M에서 분광광도법으로 연구하였다. 컴퓨터 프로그램 SQUAD를 스팩트라 데이터로부터 원하는 정보를 얻는데 사용하였다. Fitting 과정의 output은 안정도 상수, 평가한 안정도 상수의 표준편차, 농도분포 다아그램, 모든 종의 스팩트럼 프로파일이다. Co(II), Ni(II), Cu(II), Zn(II)의 PX 착체의 안정도 순서는 Cu(II) > Co(II) > Ni(II) <TEX>${\approx}$</TEX> Zn(II) 순서이다. 이것은 이들 금속이 온들이 기하학적 경향이 다른 이유일 것이다. PX의 산성도 상수는 다른 pH 값에서 흡수 스펙트럼으로 부터 위의 조건에서 역시 결정하였다. 컴퓨터 프로그램 DATAN을 PX의 산성도 상수의 결정하는 데 사용하였다. 산성도 상수의 validity는 잘 알려진 컴퓨터 프로그램 SPECFIT/32을 사용하였다. 안정 및 산성도 상수의 용매성질, 음이온과 같은 다른 인자의 효과에 관하여 자세하게 논의하였다. The complex formation of anti-inflamatory drug piroxicam (PX, 4-hydroxy-2-methyl-N-2--pridyl-2H-1,2-benzothiazine-3-carboxadiamide-1,1-dioxide) with transition metal ions Co(II), Ni(II), Cu(II) and Zn(II) in methanol(MeOH)/water binary mixtures were studied by spectrophotometric method at 25<TEX>$^{\circ}C$</TEX>, constant pH = 5.0 and I = 0.1 M. The computer program SQUAD was used to extract the desired information from the spectral data. The outputs of the fitting processes were stability constants, standard deviations of the estimated stability constants, concentration distribution diagrams and spectral profiles of all species. The sequence of the stability constants of PX complexes with Co(II), Ni(II), Cu(II) and Zn(II) follow the Cu(II) > Co(II) > Ni(II) <TEX>${\approx}$</TEX> Zn(II) order. This may be due to different geometry tendencies of these metal ions. The acidity constants of the PX were also determined under above condition from its absorption spectra at different pH values. The computer program DATAN was used for determination of acidity constants of PX. The validity of the obtained acidity constants was checked by a well known computer program SPECFIT/32. The effects of the different parameters like solvent nature, cations characteristics on the stability and acidity constants were thoroughly discussed.

Equilibrium Studies on Complex‐Formation Reactions of Pd[(2‐(2‐aminoethyl)pyridine)(H2O)2]2+ with Ligands of Biological Significance and Displacement Reactions of DNA Constituents

AbstractThe [Pd(AEP)Cl2] complex was synthesized and characterized, where AEP = 2‐(2‐aminoethyl)pyridine. The stoichiometry and stability constants of the complexes formed between various biologically relevant ligands (amino acids, peptides, DNA constituents and dicarboxylic acids) and [Pd(AEP)(H2O)2]2+ were investigated at 25 °C and 0.1 M ionic strength. The equilibrium constants for the substitution of representative coordinated ligands such as inosine, glycine or methionine by cysteine were calculated and the concentration distribution diagrams of the various species evaluated. The kinetics of base hydrolysis of free and coordinated amino acid esters was investigated. The effects of the medium dielectric constant and temperature on the kinetics of base hydrolysis of the glycine methyl ester in the presence of the [Pd(AEP)(H2O)2]2+ complex were studied and the activation parameters ΔH≠ and ΔS≠ for the hydrolysis process were determined.(© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2009)

Experimental and computational study on the aqueous acidity constants of some new aminobenzoic acid compounds

The acidity constants of three new aminobenzoic acid derivatives were determined using potentiometric and spectrophotometric methods in 0.10 M aqueous potassium nitrate solution as supporting electrolyte. The potentiometric data and UV–Vis absorption spectra of solutions were recorded in the course of their pH-metric titration with a standard base solution. The protolytic equilibrium constants, concentration distribution diagrams and number of components involved have been calculated. The relative p K a values for three acids were also calculated using ab initio quantum mechanical method at the HF/6-31G** level of theory in combination with CPCM continuum solvation method. The influence of substituents on the ionization constants of the studied molecular structures was investigated. The satisfactory agreement between the experimentally derived and theoretically calculated p K a values provides solid support for the acid–base reactions proposed in this work.

Equilibrium and Kinetic Investigations of the Interaction of Model Platinum(II) Complex with DNA Constituents in Reference to the Antitumour Activity: Complex‐Formation Reactions of [Pd(N,N‐diethylethylenediamine)(H2O)2]2+ with Ligands of Biological Significance and Displacement Reactions of DNA Constituents

The [Pd(DEEN)Cl2] and [Pt(DEEN)Cl2] complexes were synthesized and characterized where DEEN = N,N-diethylethylenediamine. 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 37°C and 0.16 M ionic strength. The stability constant of the complexes formed in solution were determined and the binding centres of the ligands were assigned. The concentration distribution diagrams of the complexes were evaluated The equilibrium constants for the displacement of representative coordinated ligands such as inosine, glycine or methionine by cysteine were calculated and the concentration distribution diagrams of the various species were evaluated. The kinetics of base hydrolysis of free and coordinated S-methylcysteine methyl ester was investigated. The mechanism of hydrolysis was discussed.

Coordination properties of dehydroacetic acid – binary and ternary complexes

Complex formation equilibria of dehydroacetic acid with Cu2+, Ni2+, Co2+, Zn2+ and Mn2+ and the ternary complexes involving Cu2+, dehydroacetic acid and some amino acids containing different functional groups are investigated. Stoichiometry and stability constants for the complexes are estimated at 25°C and 0.1 M ionic strength in 25% dioxane-water mixtures. The concentration distribution diagrams of the complexes were evaluated. The effect of temperature and organic solvent on the acid dissociation constant of dehydroacetic acid and the formation constant of Cu2+ complex was studied and thermodynamic parameters calculated.

Equilibrium Study and Biological Activity of Cu(II) with Polyvinyl alcohol(PVA) and Some Amino acids and DNA

This study presents the acid-base equilibrium of polyvinyl alcohol (PVA). The stability constant values of the binary and ternary complexes formed in solution among polyvinyl alcohol, Cu (II), some amino acids and DNA were determined potentiomertically. The stability constants of the complexes are determined and the concentration distribution diagrams of the complexes are evaluated. The ligand and their metal chelates have been screened for their antimicrobial activities using the disc diffusion method against the selected bacteria and fungi. Binary and ternary complexes of copper (II) involving polyvinyl alcohol (PVA) and various biologically relevant ligands containing different functional groups, were investigated. The ligands (L) are amino acids and DNA constituents. The ternary complexes of amino acids and DNA are formed by simultaneous reactions respectively. The results showed the formation of Cu (PVA) (L) complexes with amino acids and DNA. Amino acids form both Cu (PVA)(L) complexes and the corresponding protonated Cu(PVA)(LH) and deprotonated species Cu(PVA)(LH−1). The ternary complexes of copper (II) with (PVA) and DNA are formed in a stepwise process, whereby binding of copper (II) to (PVA) is followed by ligation of the DNA components. DNA constituents form 1:1 complexes with Cu (PVA). The stability of these ternary complexes was quantitatively compared with their corresponding binary complexes in terms of the parameter ∆ log10K. The values of ∆ log10K indicate that the ternary complexes containing aromatic amino acids were significantly more stable than the complexes containing alkyl- and hydroxyl alkyl substituted amino acids. The concentration distribution of various complex species formed in solution was also evaluated as a function of pH. The antimicrobial activities using the disc diffusion method against some selected bacteria and fungi. The activity data show that the metal complexes are found to have antibacterial and antifungal activity.

INTERACTION OF DIMETHYLTIN(IV) DICHLORIDE WITH, BIDENTATE AMINE: SYNTHESIS AND EQUILIBRIUM STUDIES.

The interaction of dimethyltin(IV) with some selected aliphatic and aromatic diamines was described. A series of diamine complexes were synthesized and characterized by elemental analysis. The stoichiometry and stability constants for the complexes are estimated at 25°C and 0.lM ionic strength. The concentration distribution diagrams of the complexes were evaluated. The effect of pKa of the diamine on the stability constant of the complex was elucidated.