Formation Of Mixed-ligand Complexes Research Articles

Mixed-ligand complex formation equilibria of copper(II), salicylic acid and some amino acids

In this work, the formation of binary and ternary complexes between copper(II), salicylic acid (H2Sal), and between copper(II), salicylic acid (H2Sal) and the amino acids: glycine (HGly), proline (HPro), α-alanine (Hα-Ala), β-Alanine (Hβ-Ala), aspartic acid (H2Asp), glutamic acid (H2Glu) and Histidine (HHis) were studied in aqueous solution at 25°C using 1.0mol·dm−3 KNO3 as the ionic medium. The analysis of the potentiometric data using the least squares computational program LETAGROP indicates the formation of the species Cu(Sal), [Cu(Sal)(OH)]−, [Cu(Sal)2]2−, and [Cu(Sal)2(OH)]3− in the binary Cu(II)-H2Sal system. In the ternary Cu(II)-H2Sal-L where H2L=H2Asp, H2Glu the complexes [Cu(Sal)(HL)]−, [Cu(Sal)(L)]2− and [Cu(Sal)(L)(OH)]3− were observed. For the case of the Cu(II)-H2Sal-HHis system the complexes Cu(Sal)(HL), [Cu(Sal)(L)]− and [Cu(Sal)(L)(OH)]2− were detected. Finally, in the Cu(II)-H2Sal-HL where H2L=glycine (HGly), proline (HPro), α-alanine (Hα-Ala), or β-Alanine (Hβ-Ala) the complexes [Cu(Sal)(L)]− and [Cu(Sal)(L)(OH)]2− were observed.

Potentiometric, Thermodynamics and Coordination Properties for Binary and Mixed Ligand Complexes of Copper(II) with Imidazole-4-acetic Acid and Tryptophan or Phenylalanine Aromatic Amino Acids

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 Δlog10 K, Δlog10 β and log10 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 (log10 β) of imidazole-4-acetic acid and its binary Cu(II)–IMA complexes were determined potentiometrically over a wide range of solvent composition.

Thermodynamic study of heteroligand complex formation of copper(II) and nickel(II) nitrilotriacetates with amino acids in solution

Ternary complexes of copper(II) and nickel(II) nitrilotriacetate (MNta) with arginine (Arg), serine (Ser), glycine (Gly), aspartic acid (Asp), and iminodiacetic acid (Ida) have been calorimetrically, potentiometrically, and spectrophotometrically studied in aqueous solution at 298.15 K and ionic strength 0.5 (KNO3). The thermodynamic parameters of mixed-ligand complex formation have been determined. The probable coordination modes of amino acid residues in the heteroligand complexes were discussed.

Preparation and application prospects metal containing biocorrectors as part of film coverings to maintain human health

The study of mixed-ligand complex formation is important problem of coordination chemistry currently. The ligands of different nature within the domestic environment of the complex, have a mutual influence, changing the chemical properties of complexes (acid-base, oxidation-reduction, the rate of ligand substitution in the internal environment) and their biological activity. According to the literature, the issues of mutual influence of ligands, which leads to a change in the reactivity of the complexes have been widely studied with the assistance of ligands of different nature. In recent years sharply increased interest in nanoobjects of different nature. This is due to the fact that many of the physical, chemical and biological properties of the nanoparticles significantly different characteristics from those of larger (macroscopic) objects. The aim of the study was to examine the conditions of formation (ratio of components, acidity) in solutions of mixed-metal biocomplexes copper. The studies have shown that the conditions of synthesis have significant impact on obtaining nanoparticles of zinc, copper and cobalt. The study of morphology and size of the resulting nanoparticles were performed on a scanning electron microscope Quanta FEG 650 in high vacuum (pressure in the chamber 8⋅10-3 to 3⋅10-3 Pa) mode. The resulting nanoparticles are studied metal particles kanglomeraty complex structure of various shapes and sizes up to 200 nm, and the crystals are spherical shape sizes of 40–90 nm. It is shown that metal complexation with drugs (ligands) leads to improvement of antimicrobial activity spectrum and expansion relative to the parent ligands, the studied biocomplexes are harmless biologically active substances, which can be recommended for further study.

Mixed-ligand complex formation equilibria of vanadium(III) with 1,10′-Phennanthroline and the amino acids glycine, proline, α-alanine and β-alanine

In this work, we present the results of the speciation of the ternary vanadium(III)-1,10-Phennanthroline(Phen) and the amino acids glycine (HGly), proline (HPro), α-alanine (HαAla) and β-alanine (HβAla) by means of potentiometric measurements in 3.0mol∙dm−3 KCl at 25°C. The experimental data were analyzed by means of the computational least-squares program LETAGROP, taking into account the hydrolysis of the vanadium(III) cation and the respective stability constants of the binary complexes and the acid base reactions of the ligands which were kept fixed during the analysis. In the systems studied the complexes [V2O(Phen)(L)]3+, [V2O(Phen)2(L)2]2+ and V(OH)2(Phen)(L) were observed, where L represents the deprotonated form of the amino acids studied in this work. The qualitative analysis of the spectrophotometric measurements corroborates the oxo-dimer formation in these complexes studied. The respective stability constants were determined and the species distribution diagrams as a function of pH were briefly discussed.

OLED thin film fabrication from poorly soluble terbium o-phenoxybenzoate through soluble mixed-ligand complexes

Features and advantages of the approach of the luminescent thin film deposition of non-volatile and non-soluble lanthanide aromatic carboxylates were exemplified by thin film deposition of terbium o-phenoxybenzoate Tb(pobz)3(H2O)2 (I) with quantum yield measured to be 96%. This approach is based on the formation and decomposition of mixed-ligand complexes, and thus mixed-ligand complex Tb(pobz)3(MG)(H2O)2 (II) (MG – monoglyme) was synthesized, characterized and used as a precursor for I thin films. Electroluminescent (EL) properties of high quality thin films of I and those with suitable host material were studied in a series of OLED devices.

Mixed Ligand Complex Formation of Cetirizine Drug with Bivalent Transition Metal(II) Ions in the Presence of 2-Aminomethylbenzimidazole: Synthesis, Structural, Biological, pH-Metric and Thermodynamic Studies

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)(NO3)(H2O)2]·nH2O 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).

Surprising Coordination Chemistry of Cu+Cations in Zeolites: FTIR Study of Adsorption and Coadsorption of CO, NO, N2, and H2O on Cu–ZSM-5

Cations exchanged in zeolites are generally characterized by a low coordination number and can thus attach simultaneously more than one small guest molecule. For instance, Cu+ ions in ZSM-5 can accept, at low temperature, up to three CO and up to two NO molecules. However, only one N2 molecule can be coordinated to such sites. Although mixed aqua-carbonyl and aqua-dinitrogen complexes are formed, no mixed carbonyl-nitrosyl, carbonyl-dinitrogen, or nitrosyl-dinitrogen species can be produced. Thus, adsorption of NO on CO precovered sample results in segregation of the CO adsorption layer according to the reaction: 2Cu+–CO + 2NO → Cu+(CO)2 + Cu+(NO)2. Adsorption of N2 on NO precovered sample leads to a similar process: 2Cu+–NO + N2 → Cu+(NO)2 + Cu+–N2. No carbonyl-dinitrogen complexes are produced during CO–N2 coadsorption. The role of the ligand and the nature of the bond in the formation of geminal and mixed-ligand complexes are discussed.

Mixed-ligand complex formation equilibria of vanadium(III) with picolinic and dipicolinic acids with some dicarboxylic acids (oxalic, malonic, and phthalic acids) studied in 3.0 M KCl at 25 °C

The ternary complexes formed between vanadium(III) and picolinic acid (Hpic) and dipicolinic acid (H2dipic) with the dicarboxylic oxalic, malonic, and phthalic acids (H2ox), (H2mal), and (H2phtha) briefly (H2L) were studied in aqueous solution by means of electromotive forces’ measurements emf(H) at 25 °C and 3.0 mol dm−3 KCl as ionic medium. The potentiometric data were analyzed using the least-squares computational program LETAGROP, considering the hydrolysis products of the V(III), the acidity constants of the ligands employed, and the formation constants of the binary complexes, obtaining the complexes V(pic)(ox), log β1,1,1,−3 = 5.39(7) and [V(pic)2(ox)]−, log β1,2,1,−4 = 4.3(1); V(pic)(ma), log β1,1,1,−3 = 5.58(5) and [V(pic)2(ox)]−, log β1,2,1,−4 = 5.00(8); V(pic)(phtha), log β1,1,1,−3 = 5.66(6) and [V(pic)2(phtha)]− log β1,2,1,−4 = 4.5(2) in the vanadium(III)-Hpic-H2L system. In the case of the vanadium(III)-H2dipic-H2L system, the complexes [V(dipic)(ox)]−, log1,1,1,−4 β = 9.3(2), [V(dipic)(Hox)(ox)]2−, log β1,1,2,−5 = 11.2(2) and [V(dipic)(ox)2]3−, log β1,1,2,.6 = 5.7 max 7.0; [V(dipic)(ma)]−, log β1,1,1,−4 = 8.7(2), [V(dipic)(Hma)(ma)]2−, log β1,1,2,−5 = 10.3(1) and [V(dipic)(ma)2]3−, log β1,1,2,.6 = 6.9(1); [V(dipic)(phtha)]−, log β1,1,1,−4 = 10.9(1), [V(dipic)(Hphtha)(phtha)]2−, log β1,1,2,−5 = 9.2 max 10.4 and [V(dipic)(phtha)2]3−, log β1,1,2,.6 = 6.9(3) were observed.

Thermodynamics, Chemical Speciation and Complex Formation Equilibria Studies of Binary and Mixed Ligand Complexes of Cu(II) with 2,2′-Bipyridyl and Some Aromatic Diamines

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−3 of NaNO3. 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 Δlog10K, Δlog10β and log10X. 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.

Synthesis, structural and electrochemical properties of nickel(II) sulfamethazine complex with diethylenetriamine ligand

In this study, [Ni(dien)2]⋅smz2⋅(Hsmz: sulfamethazine and dien: diethylenetriamine) complex has been synthesized and its crystal structure has been determined by X-ray diffraction technique. The title complex crystallizes in orthorhombic system with space group Pbnb [a=8.556(5), b=16.228(5), c=28.209(5)Å, V=3917(3)Å3 and Z=4]. The nickel(II) ion has distorted octahedral coordination geometry. The metal atom, which rides on a crystallographic center of symmetry, is coordinated by six nitrogen atoms of two dien ligands to form a discrete [Ni(dien)2]2+ unit, which captures two sulfamethazine ions, each through intermolecular hydrogen bonds. The powder EPR spectrum of Cu2+ doped Ni(II) complex was recorded at room temperature. The vibrational investigation has been carried out by considering the characteristic bands related to the functional groups of the complex. The electrochemical behavior of Ni(II) ions in the presence and in the absence of smz and dien were studied by square wave and cyclic voltammetry. A well-defined irreversible peak at −1.112V different from those of the Ni(II)-smz (−0.876V) and the Ni(II)-dien complex (−1.064V) was observed in the solution containing Ni(II) ions, which was attributed to the formation of the new mixed ligand complex of Ni(II) with smz and dien.

Formation of mixed-ligand complexes of Pd2+ with nucleoside 5'-monophosphates and some metal-ion-binding nucleoside surrogates.

Formation of mixed-ligand Pd2+ complexes between canonical nucleoside 5'-monophosphates and five metal-ion-binding nucleoside analogs has been studied by 1H-NMR spectroscopy to test the ability of these nucleoside surrogates to discriminate between unmodified nucleobases by Pd2+-mediated base pairing. The nucleoside analogs studied included 2,6-bis(3,5-dimethylpyrazol-1-yl)-, 2,6-bis(1-methylhydrazinyl)- and 6-(3,5-dimethylpyrazol-1-yl)-substituted 9-(β-d-ribofuranosyl)purines 1–3, and 2,4-bis(3,5-dimethylpyrazol-1-yl)- and 2,4-bis(1-methylhydrazinyl)-substituted 5-(β-d-ribofuranosyl)-pyrimidines 4–5. Among these, the purine derivatives 1-3 bound Pd2+ much more tightly than the pyrimidine derivatives 4, 5 despite apparently similar structures of the potential coordination sites. Compounds 1 and 2 formed markedly stable mixed-ligand Pd2+ complexes with UMP and GMP, UMP binding favored by 1 and GMP by 2. With 3, formation of mixed-ligand complexes was retarded by binding of two molecules of 3 to Pd2+.

Mixed ligand complex formation equilibria of some toxic metal ions with L-phenylalanine and maleic acid in CTAB-water mixtures

Mixed ligand complex formation equilibria of some toxic metal ions with L-phenylalanine and maleic acid in CTAB-water mixtures

Thermodynamics of mixed-ligand complex formation of zinc nitrilotriacetate with amino acids and dipeptides in solution

The isothermal calorimetry, pH-potentiometric titration and 1H and 13C NMR methods has been used to study the mixed-ligand complex formation in the systems Zn2+–Nta3––L− (L=His, Orn, Lys, GlyGly, AlaAla) in aqueous solution at 298.15K and the ionic strength of I=0.5 (KNO3). The thermodynamic parameters of formation of the mixed complexes have been determined. The relationship between the probable coordination modes of the complexone and amino acid or dipeptide molecules in the mixed-ligand complex and the thermodynamic parameters has been discussed.

Mixed-Ligand Complex Formation Equilibria of Copper(II) with 6-Methylpicolinic Acid and Some Amino Acids

In this work, the ternary complex formation among copper(II), 6-methylpicolinic acid (H6Mepic) as primary ligand, and the amino acids aspartic acid (H2Asp), glutamic acid (H2Glu) and histidine (HHis) as secondary ligands, were studied in aqueous solution at 25 °C using 1.0 mol·dm−3 KNO3 as the ionic medium. Analysis of the potentiometric data using the least squares computational program LETAGROP indicates formation of the species [Cu(6Mepic)]+, Cu(6Mepic)(OH), [Cu(6Mepic)(OH)2]−, Cu(6Mepic)2 and [Cu(6Mepic)3]− in the binary Cu(II)–H6Mepic system. In the ternary Cu(II)–H6Mepic–H2Asp system the complexes [Cu(6Mepic)(H2Asp)]+, Cu(6Mepic)(HAsp), [Cu(6Mepic)(Asp)]− and [Cu(6Mepic)(Asp)(OH)]2− were observed. In the case of the Cu(II)–H6Mepic–H2Glu system the complexes Cu(6Mepic)(HGlu), [Cu(6Mepic)(Glu)]−, [Cu(6Mepic)(Glu)(OH)]2− and [Cu(6Mepic)(glu)(OH)2]3− were detected. Finally, in the Cu(II)–H6Mepic–HHis system the complexes [Cu(6Mepic)(HHis)]+, Cu(6Mepic)(His) and [Cu(6Mepic)(His)(OH)]− were observed. The species distribution diagrams as a function of pH are briefly discussed.

Kinetics of oxidation of glutathione by an octahedral cobalt(III) complex with phenolate–amide–amine coordination

The reduction of the octahedral cobalt(III) complex CoIII(HL)·9H2O, H4L = 1,8-bis(2-hydroxybenzamido)-3,6-diazaoctane by glutathione (GSH) has been studied by conventional spectrophotometry at 25.0 ≤ t/°C ≤ 45.0, 0.02 ≤ [H+]/mol dm−3 ≤ 0.20 and I = 0.3 mol dm−3 (NaClO4). The reaction is biphasic. The fast initial phase is attributed to the H+-induced formation of the mixed ligand complex, [CoIII(H2L)GSH]+, for which the rate-limiting step is the chelate ring opening via CoIII–NH (amide–N) bond cleavage of the protonated species, [CoIII(H2L)]+. Outer-sphere association equilibria between GSH/GSH2 + and [CoIII(H2L)]+ substantially retard the ring opening process and consequently the mixed ligand complex formation. This is then followed by a slow phase involving reduction of [CoIII(H2L)GSH]+ by both GSH and GSH2 +. The final products are the corresponding Co(II) complex and the oxidized form of GSH, GS–SG. The kinetic data and activation parameters for the redox process are interpreted in terms of an outer-sphere electron transfer mechanism.

Thermodynamic study of mixed-ligand complex formation of copper(II) and nickel(II) nitrilotriacetates with dipeptides in solution

The mixed-ligand complex formation in the systems M2+–Nta3−–L− (M=Cu, Ni; L=GlyGly, AlaAla) has been calorimetrically, pH-potentiometrically and spectrophotometrically studied in aqueous solution at 298.15K and the ionic strength of I=0.5 (KNO3). The thermodynamic parameters of formation of the MNtaL2− and MNtaLH-13- complexes have been determined. The probable coordination mode of the complexone and dipeptide molecules in the mixed-ligand complexes was discussed.

Mixed ligand complex formation of 2-aminobenzamide with Cu(II) in the presence of some amino acids: Synthesis, structural, biological, pH-metric, spectrophotometric and thermodynamic studies

Mixed ligand Cu(II) complexes of 2-aminobenzamide (2AB) and amino acids viz., glycine (gly), l-alanine (ala), l-valine (val) and l-phenylalanine (phe) have been synthesised and characterized by various physico-chemical and spectral techniques. The calculated g-tensor values for Cu(II) complexes at 77K and 300K, show the distorted octahedral geometry which has been confirmed from the absorption studies. Consequently, the thermal studies illustrate that the loss of water and acetate molecules in the initial stage which are followed by the decomposition of organic residues. The powder X-ray diffraction and SEM analysis reflect that all the complexes have well-defined crystallinity nature with homogeneous morphology. The binding activities of CT DNA with CuAB complexes have been examined by absorption studies. Further, the oxidative cleavage interactions of 2-aminobenzamide and CuAB complexes with DNA were studied by gel electrophoresis method in H2O2 medium. Also, the complex formation of Cu(II) involving 2-aminobenzamide and amino acids were carried out by a combined pH-metric and spectrophotometric techniques in 50% (v/v) water-ethanol mixture at 300, 310, 320 and 330±0.1K with I=0.15moldm−3 (NaClO4). In solution, CuAB and CuAB2 species has been detected and the binding modes of 2-aminobenzamide and amino acids in both binary and mixed ligand complexes are same. The calculated stabilization value of ΔlogK, log X and log X′ indicates higher stabilities for the mixed ligand complexes rather than their binary species. The thermodynamic parameters like ΔG, ΔH and ΔS have been determined from temperature dependence of the stability constant. In vitro biological activities of 2-aminobenzamide, CuA and CuAB complexes show remarkable activities against some bacterial and fungal strains. The percentage distribution of various binary and mixed ligand species in solution at dissimilar pH intervals were also evaluated.

Synthesis, characterization, mixed-ligand complex formation reactions, and equilibrium studies of Co(II) with 2,2′-dipyridylamine and some selected biorelevant ligands

Binary and ternary cobalt(II) complexes involving 2,2′-dipyridylamine and various biologically relevant ligands containing different functional groups are investigated. The ligands used are dicarboxylic acids, amino acids, and DNA unit constituents. The ternary complexes are formed by simultaneous reactions. The results showed 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. The stability of ternary complexes formed with dicarboxylic acids was quantitatively compared with their corresponding binary complexes in terms of the ∆log10 K parameters. The concentration distribution of the complexes in solution was evaluated. The solid complexes of Co(II) dipyridylamine cyclobutane-1,1-dicarboxylate, or malonate, oxalate, and succinate have been synthesized and characterized by elemental analysis, infrared spectra, magnetic, and conductance measurements. Spectroscopic studies and M eff values suggest a tetrahedral geometry for the cobalt(II) complexes. The effect of temperature on the formation constant of the complexes was studied, and the thermodynamic parameters were calculated. Formation of the metal complexes has been found to be spontaneous, exothermic, and entropically favorable.

Thermodynamic study of mixed-ligand complex formation of copper(II) and nickel(II) nitrilotriacetates with amino acids in solution. I

Mixed-ligand complex formation in the system M2+–Edta4−–L− (M=Cu, Ni; L=His, Lys, Orn, Im) has been calorimetrically, pH-potentiometrically and spectrophotometrically studied in aqueous solution at 298.15K and with an ionic strength of I=0.5 (KNO3). The thermodynamic parameters of formation of the MEdtaL, MEdtaHL and (CuEdta)2L complexes have been determined. The probable coordination mode of the complexone and the amino acid residue in the mixed-ligand complexes has been discussed.