Metal-ligand Stability Constants Research Articles

PH-metric titration technique for the study of metal-complexes of substituted 2- Oxo-2H-Chromene-3-Carbohydrazide derivatives in solution: calculation of stability constants

Background: In coordination chemistry, the stability of complexes is expressed in terms of the formation constant of complexes. In coordination complexes, the temperature is very important. It plays an important role in complex formation reaction. Temperature affects metal-ligand stability constant (log K) and proton-ligand stability constant (pK). The metal ion Mn2+, Co2+, Ni2+, and Cu2+ at different temperatures form complexes with 4-sulfamethoxazoleazo-3-methyl-2-pyrazolin-5-one are reported. The metal-ligand stability constant (logK) and proton-ligand stability constant (pK) of Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) with organic ligand n-[2-hydroxy-1-napthalydene]-2-methylanilline at 0.1 M ionic strength in 60% dioxane-water medium is studied. The study of thermodynamic parameters and stability constant of complexes of substituted thiazole Schiff bases with rare earth metal ions in mixed solvent is reported. Objective: The study of coordination compounds and a lot of work has been done on metal-ligand stability constant. The same transition metal ion form complexes with substituted pyrazole for this metal-ligand stability constant are determined. Method: Pointwise Calculation Method Half Integral Method. Result: The values of logK1 and logK2 are determined from the metal-ligand formation curve at formation numbers 0.5 and 1.5. In all cases, logK1 is greater than logK2. The ratio logK1/logK2 is positive and greater than one in all systems. This implies that there is little or no steric hindrance to the addition of the secondary ligand molecules. The difference between logK1 - logK2 is usually positive. If the difference between logK1 and logK2 is less than 2.5, simultaneous formation of 1:1 and 1:2 complexes occurs and if it is more than 2.5, then stepwise complex formation occurs. In the present case, in all systems, it is less than 2.5. This indicates the simultaneous formation of 1:1 and 1:2 complexes takes place. Conclusion: A pH-metric study of Substituted 2-oxo-2H-chromene-3-carbohydrazide derivatives with metal ions Fe(III), and Mn(II) occurs. The graphical representation of the curve shows that the acid + ligand curve is separated from the corresponding acid + ligand + metal curve in this system. The formation of a complex is indicated. Half integral method and pointwise calculation method give nearly similar results. The values of stability constants for all systems indicate that the complexes formed in these processes are stable.

Effect Of Solvents On Stability Constants of Fe(II) and Ni(II) Transition Metal Ions Chelates With Some Substituted Pyrazoles

The reaction of Fe(II) and Ni (II) metal ions with L1 : 3 (2’- chlorophenyl) - 4- benzoyl - 5 (2-hydroxy phenyl) pyrazole, L2: 3 (2’-chlorophenyl) - 4- pyridoyl -5 (2-hydroxy phenyl) pyrazole , L3: 3 (2’-aminophenyl)- 4-pyridoyl - 5 (2- hydroxyl phenyl) pyrazole and L4: 3 (4’-chlorophenyl) -4-Benzoyl -5(2-hydroxy-phyenyl) pyrazole, at 0.1M ionic strength at 28 ± 0.10C in 70% ethanol -water mixture and 70% dioxane-water mixture have been studied pH-metrically. The data obtained were used to estimate the values of proton-ligand (pK) and metal-ligand (logK) stability constants in different solvents. It is observed that the pK and logK values in 70% dioxane-water mixture are greater than in 70% ethanol -water mixture. Fe(II) and Ni(II) metal ions formed 1:1 and 1:2 complexes with all the ligands in both solvent medium.

Determination of Stability Constant of Flurosubstituted Chlconemines for its Medicinal Efficiency

The good activity of drug is depending upon its stability constant i.e. proton ligand stability constant and metal ligand stability constant. If the stability constant is fairly very good then it should use as a good and effective medicine .In content to this in present work the proton ligand stability constant and metal ligand stability constant of fluro substituted chalconeimines L5 = 2-Hydroxy naphthalene 4-dimethyl aniline 4- fluro chalconeimine [FN] are studied with highly reactive transition metal like (Cu (II), Co(II),Cr(II) and Fe(III)). The 70% dioxane water solvent system used in the present investigation. The presence of –OH group confirmed by using of 0.1 M ionic strength. The transition metal (Cu (II),Co (II),Cr(II)and Fe(III)) used and the ligand form 1:1 and 1:2 complex with all values of log k1 and log k2 positive.

Determination of Stability Constant of The Complexes of Metal Ion Fe(III), Mn(II) And Cr(III) With Some Substituted 2-Oxo-2H-Chromene-3-Carbohydrazide Derivatives at 0.1 M Ionic Strength at 42oC

Proton ligand and metal ligand stability constant are measured for Fe(III) and 1, 2-dihydroxy benzene and 1, 5-disulphonic acid complexes . Determination of stability constant of substituted of pyrazoles with rare earth metals form complexes are reported . Effect of temperature on formation constants of 2 acetylpyridine(N benzoyl)glycine hydrazone with lanthanide(III) ions at different ionic strengths are reported. Irving and Rossotti, Herson and Gilbert , Wilkins and Lewis and Rossotti and Rossotti have determined stability constant by Bjerrum-Calvin titration technique . Kabadi , Jahagirdar and Narwade have determined pK values of salicylaldehyde, salicylic acid and sulphonic acid respectively by similar procedure. The metal ligand stability constant of some β-diketones are reported . Stability constants have investigated for some substituted pyrazolines, isoxalline and diketone . The method most frequently applied for study of complex equilibria is pH-metric titration technique . Stepwise formation of mononuclear binary complexes is described by set of equilibrium constants. For pH-metric measurements an electrode must be selected. According to Bjerrum, Martell and Calvin , the formation of complex MLN is stepwise process and one has to deal with a series of equilibria of the type: Irving and Rossotti, Herson and Gilbert , Wilkins and Lewis and Rossotti and Rossotti have determined stability constant by Calvin-Bjerrum titration technique . The value of nA,n, pK, log K1 and log K2 are evaluated by Irving and Rossotti's equation. The stability constant and thermodynamic parameters of complexes containing lighter lanthanides , copper(II) , calcium and magnesium are reported. It is also important in environmental studies , medicinal and industrial chemistry . Effects of transition metal on stability constant of complexes have studied by pH metric method . Bendi , Janrao and Ramteke have studied stability constant of ligands with lanthanide metals complexes.The present work involves pH metric study of substituted 2-oxo-2H-chromene-3-carbohydrazide derivatives with metal ions Fe(III), Mn(II), Cr(III) and Ti(III) at temperature42oC. The Bjerrum-Calvin titration technique as modified by Irving and Rossotti has been employed in the present study. The following three sets of titrations are carried out in sequence.

Practical and Computational Studies of Bivalence Metal Complexes of Sulfaclozine and Biological Studies.

In the search for novel, metal-based drug complexes that may be of value as anticancer agents, five new transition metal complexes of sulfaclozine (SCZ) with Cu(II), Co(II), Ni(II), Zn(II), and Fe(II) were successfully synthesized. The chemical structure of each complex was characterized using elemental analysis (CHN), IR spectroscopy, UV–Vis spectroscopy, thermogravimetric analysis (TGA), and electronic paramagnetic resonance (EPR) spectroscopy. IR spectra indicated that the donor atoms were one sulfonyl oxygen atom and one pyrazine nitrogen atom, which associated with the metal ions to form a stable hexagonal coordination ring. The metal–ligand stability constant (Kf) revealed that Cu(II) and Ni(II) have good coordination stability among the metal compounds. Theoretical studies using DFT/B3LYP were performed to further validate the proposed structures. The obtained results indicated that Cu(II) has a trigonal bipyramidal geometry, whereas Fe(II), Co(II), and Ni(II) have an octahedral structure, while Zn(II) has a tetrahedral arrangement. The bio-activities of the characterized complexes were evaluated using DNA binding titration and molecular docking. The binding constant values for the metal complexes were promising, with a maximum value for the copper metal ion complex, which was 9 × 105 M-1. Molecular docking simulations were also carried out to evaluate the interaction strength and properties of the synthesized metal complexes with both DNA and selected cancer-relevant proteins. These results were supported by in vitro cytotoxicity assays showing that the Cu(II) and Ni(II) complexes display promising antitumor activity against colon and breast cancer cell lines.

Phosphonate Chelators for Medicinal Metal Ions.

A family of phosphonate-bearing chelators was synthesized to study their potential in metal-based (radio)pharmaceuticals. Three ligands (H6phospa, H6dipedpa, H6eppy; structures illustrated in manuscript) were fully characterized, including X-ray crystallographic structures of H6phospa and H6dipedpa. NMR spectroscopy techniques were used to confirm the complexation of each ligand with selected trivalent metal ions. These methods were particularly useful in discerning structural information for Sc3+ and La3+ complexes. Solution studies were conducted to evaluate the complex stability of 15 metal complexes. As a general trend, H6phospa was noted to form the most stable complexes, and H6eppy associated with the least stable complexes. Moreover, In3+ complexes were determined to be the most stable, and complexes with La3+ were the least stable, across all metals. Density functional theory (DFT) was employed to calculate structures of H6phospa and H6dipedpa complexes with La3+ and Sc3+. A comparison of experimental 1H NMR spectra with calculated 1H NMR spectra using DFT-optimized structures was used as a method of structure validation. It was noted that theoretical NMR spectra were very sensitive to a number of variables, such as ligand configuration, protonation state, and the number/orientation of explicit water molecules. In general, the inclusion of an explicit second shell of water molecules qualitatively improved the agreement between theoretical and experimental NMR spectra versus a polarizable continuum solvent model alone. Formation constants were also calculated from DFT results using potential-energy optimized structures. Strong dependence of molecular free energies on explicit water molecule number, water molecule configuration, and protonation state was observed, highlighting the need for dynamic data in accurate first-principles calculations of metal-ligand stability constants.

Thermodynamic Studies of 5-(P-Bromophenylazo)-3 Phenylrhodanine and Its Metal Complexes.(Dept.P)

The dissociation constant of 5-(p-bromophenylazo)-3-phenylrhodanine (HL) and metal-ligand stability constants of its complexes with bivalent (Mn2+, Co2+, Ni2+ and Cu2+) metal icons have been determined potentiometrically in 0.1 M KCI and 40% (v/v) ethanol-water mixture. The order of the stability constants of the formed complexes was found to be Mn2+ <C02+ < Ni2+ < Cu2+. The effect of temperature was studied and the corresponding thermodynamic parameters (∆G, ∆H and ∆S) were derived and discussed. The dissociation process is nonspontaneous, endothermic and entropically unfavorable. The formation of the metal complexes has been found to be spontaneous, exothermic and entropically favorable.

Potentiometric Studies of Binary and Ternary Complexes of Transition Metal Ions with Ceftriaxone Sodium and Esomeprazole

The present paper deals with potentiometric study for formation of binary (1 : 1) and ternary (1 : 1 : 1) complexes of transition metals Ni(II), Cu(II), Co(II), and Zn(II) with Ceftriaxone Sodium and Esomeprazole in aqua-organic medium. The proton–ligand stability constant and metal–ligand stability constant has been calculated using Calvin–Bjerrum technique. The ionic strength has been maintained by 1.0 M NaClO4 and ternary complexes have been calculated by Thomson–Loraas method to determine log KMXY for all the ternary chelates.

Computer Assisted Thermal Complexation Studies of Vanadium with Benzodiazepine Drugs

The complexing tendency of vanadium with nifoxipam and lorazepam were carried out by pH metric titration technique in aqueous acid media at different temperatures (298, 308 and 318 K) and an ionic strength of 0.2 M. The degree of complexation was investigated at different pH values. Potentionmetric measurement of hydrogen ion concentration was also studied with the degree of complex formation. The proton-ligand and metal-ligand stability constants were resolved by modified Calvin-Bjerrum pH titration technique (Irving and Rossitti) using computer programming. The important thermodynamic parameters such as Gibb's free energy change (ΔG), entropy change (ΔS) and enthalpy change (ΔH) for the complexation reactions were calculated. The formation of metal complexes was found to be spontaneous, exothermic and conducive in nature at lower temperatures.

METAL-LIGAND STABILITY CONSTANTS OF Pr(III) , Nd(III) AND Sm(III) METAL IONS COMPLEXES WITH SOME SUBSTITUTED ISOXAZOLINE pH-METRICALLY

The stepwise stability constant values of substituted isoxazoline with Pr(III), Nd(III), and Sm(III) metal ion have been studied at 0.1M ionic strength pH-Metrically in 70% ethanol-water mixture by Bjerrum method as adopted by Calvin Wilson. The values of proton-ligand stability constant (pK) and metal-ligand stability constant (log K) are calculated and from the data obtained it is observed that metal ions formed 1:1 complexes with ligands L1 and L2 Â using half integral & pointwise calculation method

PH-Metric measurements of azelastine hydrochloride with Cu(II), Co(II) and Fe(II) metal ions

Proton-ligand stability constant, metal-ligand stability constants, pK and log k of azelastine hydrochloride with Cu(II), Co (II) and Fe(II) metal ions were determined by pH-metric technique. Irving-Rossotti titration technique was used for determination of stability constants. 1:1 complexes were formed in present investigation in between azelastine hydrochloride (TH) and Cu (II), Co (II) and Fe (II) metal ions.

PH-Metric study of picolinic acid with Cu (II), Co (II) and Fe(II)ions

pH-Metric measurements of picolinic acid were studied with Cu(II), Co (II) and Fe(II)metal ions at 0.2 M ionic strength in water by Irving-Rossotti titration technique for determination of stability constants. 1: 1 complexes were formed in present investigation in between picolinic acid (PA) and Cu (II), Co (II)and Fe(II) metal ions. Values of proton-ligand stability constant (pK) and metal-ligand stability constants log k were evaluate and compared from resultant data.

Synthesis, characterization, and biological activity of new mixed ligand transition metal complexes of glutamine, glutaric, and glutamic acid with nitrogen based ligands

ABSTRACTA new series of Cu(II), Co(II), Ni(II), and Fe(II) ternary complexes of glutamine, glutaric, and glutamic acid with imidazole derivatives have been synthesized. The nature of the bonding and the stereochemistry of the complexes have been deduced from elemental analyses, infrared and electronic spectra, conductivity measurements, and thermogravimetric analysis. The structure of [Co(glu)(IMI)2] and [Fe(glu)(IMI)2(H2O)2] complexes was validated using quantum mechanics calculations based on accurate DFT methods. Calculations revealed that both complexes had distorted tetrahedral geometry. In case of [Co(glu)(IMI)2], glu ligand was coordinated through the terminal part which consists of carboxylate and amine groups. The formation constants of mixed ligand complexes of copper (II) and nickel (II) with glutamic-glutamine-glutaric as primary ligands and imidazole or its derivatives as secondary ligands have been determined by pH metric technique in aqueous medium. The data obtained were used to evaluate the values of metal-ligand stability constants using Irving-Rossotti titration technique. Mixed ligand complexes studies of these metal ions have been carried pH-metrically at the same conditions. In addition, the interaction of these complexes with calf-thymus DNA (CT-DNA) was investigated at pH = 7.2 by using UV–vis absorption and viscosity measurements. Results indicated that the investigated complexes strongly bind to CT-DNA via intercalative mode. Moreover, the prepared compounds are screened for their in vitro antibacterial activity against two types of bacteria, Pseudomonas aeruginosa and Bacillus cereus. In general, based on the data obtained in this study, the synthesized metal complexes might be taken into consideration as promising antibacterial compounds.

Molecular Docking, Potentiometric and Thermodynamic Studies of Some Azo Compounds

The proton-ligand dissociation constant of 5-(4′-alkylphenylazo)-3-phenylamino-2-thioxothiazolidin-4-one (HL n ) (n = 1, R = –CH3; n = 2, –H and n = 3, –Cl) and metal–ligand stability constants of its complexes with metal ions (Mn2+, Co2+, Ni2+ and Cu2+) have been determined potentiometrically in 0.1 mol·dm−3 KCl and 40 % (by volume) DMF–water mixture and at 298, 308 and 318 K. The stability constants of the formed complexes increase with the order Mn2+ < Co2+ < Ni2+ < Cu2+. The effect of temperature was studied and the corresponding thermodynamic parameters (∆G°, ∆H° and ∆S°) were derived and discussed. The dissociation process of the ligands is endothermic and entropically unfavorable. The formation of the metal complexes has been found to be endothermic and entropically favorable. Molecular docking was used to predict the binding mode between azo rhodanine derivatives (HL n ) with the 3hb5-oxidoreductase receptor of breast cancer. The values of binding constants (K i ) of the azo rhodanine derivatives (HL n ) are correlated with Hammett’s constant (σ R).

Molecular docking, geometrical structure, potentiometric and thermodynamic studies of moxifloxacin and its metal complexes

Molecular docking was used to predict the binding between moxifloxacin (H2L) and the receptors of breast cancer mutant (3hb5), prostate cancer mutant (2q7k), crystal structure E. coli (3t88) and crystal structure of S. aureus (3q8u) and it was found that the moxifloxacin shows best interaction with 3hb5 receptor other than receptors. The geometrical structure of moxifloxacin is discussed. The proton-ligand dissociation constant of moxifloxacin (H2L) and metal-ligand stability constants of its complexes with metal ions (Mn2+, Co2+, Ni2+ and Cu2+) have been determined potentiometrically in 0.1M KCl and 10% (by volume) ethanol–water mixture. At constant temperature, the stability constants of the formed complexes increase in the order of Mn2+<Co2+<Ni2+<Cu2+. The effect of temperature was studied at 298, 308 and 318K and the corresponding thermodynamic parameters (∆G, ∆H and ∆S) were derived and discussed. The dissociation process is non-spontaneous, endothermic and entropically unfavorable. The formation of the metal complexes has been found to be spontaneous, endothermic and entropically favorable. The predicted pKa obtained by docking measurements for moxifloxacin (H2L) are in agreement with experimental values.

Molecular docking, potentiometric and thermodynamic studies of azo rhodanines

Molecular docking was used to predict the binding between azo rhodanine derivatives (HLn) with the receptor prostate cancer 2Q7K hormone. The values of dissociation constant (pKH) of azo rhodanine derivatives (HLn) are correlated with Hammett's constant (σR). The proton-ligand dissociation constant of azo rhodanine derivatives (HLn) and metal-ligand stability constants of their complexes with metal ions (Mn2+, Co2+, Ni2+ and Cu2+) have been determined potentiometrically in 0.1M KCl and 40% (by volume) ethanol–water mixture and at 298, 308 and 318K. The stability constants of the formed complexes increase with the order Mn2+<Co2+<Ni2+<Cu2+. The effect of temperature was studied and the corresponding thermodynamic parameters (ΔG, ΔH and ΔS) were derived and discussed. The dissociation process of the ligands is non-spontaneous, endothermic and entropically unfavorable. The formation of the metal complexes has been found to be spontaneous, endothermic and entropically favorable.

Potentiometric, thermodynamics and theoretical calculations of some rhodanine derivatives

A series of 5-(4′-alkylphenylazo)-3-phenylamino-2-thioxothiazolidin-4-one (HLn) have been prepared and characterized by elemental analysis, 1H NMR and IR spectra. X-ray diffraction pattern of ligand (HL2) was studied. The geometrical structures of these ligands are carried out by HF method with 3-21G basis set. Proton-ligand dissociation constant of ligands (HLn) and their metal–ligand stability constants of Mn2+, Co2+, Ni2+ and Cu2+ have been determined potentiometrically in 0.1M KCl and 30% (v/v) DMSO–water mixture at 298, 308 and 318K. The stability constants of the formed complexes increase with the order: Mn2+<Co2+<Ni2+<Cu2+. The effect of temperature was studied and the corresponding thermodynamic parameters (ΔG, ΔH and ΔS) were derived and discussed. The dissociation process is non-spontaneous, endothermic and entropically unfavorable. The formation of the metal complexes has been found to be spontaneous, endothermic and entropically favorable. Proton–ligand dissociation constant (pKH) of the ligands increases according to the following order p-(OCH3>H>NO2) as expected from Hammett's constant (σR).

Molecular docking, potentiometric and thermodynamic studies of some azo quinoline compounds

The ligands of 5-(4-derivative phenyl azo)-8-hydroxyquinoline and its derivatives (HLn) were synthesized from the coupling of the quinoline with diazonium salt derived from aniline and its p-derivatives and characterized by different spectroscopic techniques. Molecular docking was used to predict the binding between azo compounds with the receptor of breast cancer mutant 3hb5-oxidoreductase. The X-ray diffraction, XRD, pattern of the ligand (HL3) is polycrystalline nature. The proton-ligand dissociation constant of the azo compounds (HLn) and metal–ligand stability constants of their complexes with metal ions (Mn2+, Co2+, Ni2+ and Cu2+) have been determined by potentiometric technique in 0.1M KCl and 50% (by volume) DMF–water mixture. For the same ligand at constant temperature, the stability constants of the formed complexes increase in the order Mn2+, Co2+, Ni2+ and Cu2+. The effect of temperature was studied at 298, 308 and 318K and the corresponding thermodynamic parameters (∆G, ∆H and ∆S) were derived and discussed. The dissociation process is non-spontaneous, endothermic and entropically unfavorable. The formation of the metal complexes has been found to be spontaneous, endothermic and entropically favorable.

Proton/metal–ligand stability constants of сomplexes of Ni(II), Cu(II), and Co(II) with diethyl 4-(substituted-phenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate in 70% dioxane–water mixture

Physico-chemical properties viz proton–ligand and metal–ligand stability constants of complexes of diethyl 4-(substituted-phenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate with Ni(II), Cu(II), and Co(II) were determined in mixed solvents (70% dioxane). Presence of OH/NH group(s) in these compounds was confirmed at 0.1 M ionic strength in 70% dioxane-water mixture pH-metrically. It is observed that Ni(II), Cu(II), and Co(II) metal ions formed 1: 1 and 1: 2 complex with all the three ligands. The results show that the ratio of logK1/logK2 is positive in all cases. This implies that there is little or no steric hindrance to the addition of secondary molecules.

Molecular docking, theoretical calculations and potentiometric studies of some azo phenols

The ligands 5-amino-2-(phenyldiazenyl)phenol and its derivatives (HLn) were synthesized from the coupling of 3-aminophenol with aniline and its p-derivatives and characterized by different spectroscopic techniques. The molecular and electronic structures of the investigated compounds (HLn) were also studied using quantum chemical calculations. Molecular docking was used to predict the binding between azo compounds with the receptor of prostate cancer 2q7k-Hormone and 3hb5-oxidoreductase receptor of breast cancer. The proton–ligand dissociation constant of the azo compounds (HLn) and metal–ligand stability constants of their complexes with metal ions (Mn2+, Co2+, Ni2+ and Cu2+) have been determined by potentiometric technique in 0.1M KCl and 40% (by volume) DMF–water mixture. For the same ligand at constant temperature, the stability constants of the formed complexes increase in the order Mn2+, Co2+, Ni2+ and Cu2+. The effect of temperature was studied at 303, 313 and 323K and the corresponding thermodynamic parameters (∆G, ∆H and ∆S) were derived and discussed. The dissociation process is non-spontaneous, endothermic and entropic ally unfavorable. The formation of the metal complexes has been found to be spontaneous, endothermic and entropic ally favorable.