Stability Constants Of Binary Complexes Research Articles

Copper(II) ion catalytic oxidation of o-phenylenediamine and characterization, X-ray crystal structure and solution studies of the final product [DAPH][H3O][Cu(dipic)2]·3H2O

The complex [DAPH][H3O][Cu(dipic)2]·3H2O, (1) (dipicH2=2,6-pyridinedicarboxylic acid and DAP=2,3-diaminophenazine) was prepared from the reaction of Cu(NO3)2·2H2O with mixture of o-phenylenediamine (OPD) and 2,6-pyridinedicarboxylic acid in water. The complex was characterized by FTIR, elemental analysis, UV–Vis and the single-crystal X-ray diffraction. The crystal system is monoclinic with the space group P21/c. This complex is stabilized in the solid state by an extensive network of hydrogen bonds between crystallized water, anionic and cationic fragments, which form a three-dimensional network. Furthermore, hydrogen bonds, π⋯π and CO⋯π stacking interactions seem to be effective in stabilizing the crystal structures. The protonation constants of dipic (L) and DAP (Q), the equilibrium constants for the dipic–DAP proton transfer system and the stoichiometry and stability constants of binary complexes including each of ligands (dipic, DAP) in presence Cu2+ ion, ternary complexes including, both of ligands (dipic–DAP) in presence of metal ion were calculated in aqueous solutions by potentiometric pH titration method using the Hyperquad2008 program. The stoichiometry of the most complexes species in solution was found to be very similar to the solid-state of cited metal ion complex.

The Zinc(II) Coordination Polymer with Mixed-Ligand of 4-Hydroxypyridine-2,6-dicarbolic Acid and Benzene-1,2,4,5-tetracarboxylic Acid in the Presence of Piperazine as a Counter Ion: Synthesis, Crystal Structure and Solution Study

Mixed-ligand zinc(II) complex, {(pipzH2)[Zn(hypydc)(btc)0.5]·H2O} n , (1) was prepared with 4-hydroxypyridine-2,6-dicarboxylic acid (hypydcH2), benzene-1,2,4,5-tetracarboxylic acid (btcH4) and piperazine (pipz). This compound is composed of an anionic complex, [Zn(hypydc)(btc)0.5]2−, protonated piperazine as a counter-ion, (pipzH2)2+ and one uncoordinated water molecule. The three donor atoms of the (hypydc)2− and two donor atoms of bridged (btc)4− ligands form a distorted square pyramid arrangement around the ZnII center. In the crystal structure of the title compound, a wide range of non-covalent interactions consisting of hydrogen bonding (of the types of O–H···O, N–H···O and C–H···O with D···A ranging from 2.630(2) to 3.347(3) A, ion pairing and C–O···π stacking interactions connect the various components into a supramolecular structure. The quaternary complex system including of hypydcH2–btcH4–pipz and Zn2+ ion, has been investigated. The stoichiometry and stability constants of binary complexes including each of ligands (hypydcH2, btcH4, pipz) in presence of Zn2+ ion, ternary complexes including each two of three ligands (hypydcH2–btcH4, hypydcH2–pipz, btcH4–pipz) in presence of metal ion and finally quaternary systems including three ligands (hypydcH2–btcH4–pipz) and Zn2+ ion were calculated in aqueous solutions by potentiometric pH titration method. A novel polymeric mixed-ligand zinc(II) complex, {(pipzH2)[Zn(hypydc)(btc)0.5]·H2O} n containing 4-hydroxypyridine-2,6-dicarboxylic acid, benzene-1,2,4,5-tetracarboxylic acid and piperazine was synthesized and characterized.

Potentiometric and quantum studies of the speciation of phenoxyacetic acids in the presence of mercury (II) and of lead (II)

The stability constants of binary complexes of 2,4-dichlorophenoxyacetic acid (2,4-D), (4-chloro-2-methylphenoxy)acetic acid (2,4-MCPA) and (4-chloro-2-methylphenoxy) propionic acid (2,4-MCPP) with Hg(II), Pb(II) have been calculated at 298 K and at ionic strength μ = 0.1 (NaNO3). Potentiometric measurements display two hydroxide complexes for Hg(II): HgH−1A and HgH−2A2 whereas for Pb(II) we observe the formation of three species PbH−1A, PbH−1A2 and PbH−2A2. With regard to the successive complexes, no other system represents this type of complexes under our experimental conditions. The order of capacity of complexation compared to metal for the three ligands is Hg(II)4Pb(II). Finally, the study in solution has been completed by a quantum examination of the structures of the complex of Hg(II) by the AM1 method.

Studies on the Synthesis and Thermodynamic Stability of Two Multidentate Ligands 2,9-disubstituted 1,10-phenanthroline

Two multidentate ligands: N,N′-di-(propionic acid-2′-yl-)-2,9-di-aminomethylphenanthroline (L1) and N,N′-di-(3′-methylbutyric acid-2′-yl-)-2,9-di-amino-methylphenanthroline (L2) were synthesized and fully characterized by 1H NMR and elemental analysis. The binding ability of L1 and L2 to metal ions such as M(II) (M = Cu, Zn, Co and Ni) and Ln(III) (Ln = La, Nd, Sm, Eu, and Gd) has been investigated by potentiometric titration in aqueous solution and 0.1 mol dm−3KNO3 at 25.0 ± °C. In view of the structure of L1 and L2, mononuclear metal complexes can be formed in solution. The stability constants of binary complexes of ligands L1 and L2 with metal ions M(II) and Ln(III) have been determined respectively and further discussed.

Potentiometrie examination of complexation equilibria of some phenoxyacetic acid derivatives with Cu(II), Cd(II) and Zn(II)

The stability constants of binary complexes of 2,4-dichlorophenoxyacetic acid (2,4-D), (4-chloro-2-methylphenoxy)acetic acid (2,4-MCPA) and (4-chloro-2-methylphenoxy) propionic acid (2,4-MCPA) with Cu(II), Cd(II) and Zn(II) have bean calculated at 298 K and at ionic strength μ = 0.1 (NaNO3). Potentiometric measurements display three hydroxide complexes: MH-1A, MH-1A2 and MH-2A2. With regard to the successive complexes, no other system represents this type of complexes under our experimental conditions. The order of capacity of complexation compared to metal for the three ligands is Cu(II)>Zn(II)>Cd(II).

Efficiency of chelators in reversal of zinc-mediated cellular reactions in cultured lung cells

Previous work using pulmonary cells in vitro indicated that inhibition of protein synthesis is an early and useful parameter in assessing zinc-mediated cellular toxicity. We now have studied the restoration of protein synthesis with various zinc-chelating antidotes in cultured lung cell lines (A549, L2, 11Lu) after ZnCl2 treatment. After treatment with 75–200 μM ZnCl2 for 1–5 h to inhibit protein synthesis to 10–20% of control values, cells were incubated in medium supplemented with either histidine [HIS], succinic acid [SUCC], ethylenediaminetetraacetic acid [EDTA], 2,3-dimercaptopropane-1-sulfonate [DMPS], d-penicillamine [dPA], or N-acetylcysteine [NAC], or ethylenediamine [ED] in 10-fold molar excess over original zinc concentration. Alternatively, 2,3-dimercaptopropanol [BAL] was added at a concentration of 400 μmol/l (2–5.3-fold molar excess). Recovery of cellular function was assessed by measuring the increase of inhibited methionine incorporation. Antidote treatment elevated protein synthesis in the following order: DMPS ≥ dPA > BAL ≥ EDTA ≥ NAC ≥ HIS > SUCC ≥ ED. Small differences were seen between the cell lines. HIS was effective in A549 cells only, whereas NAC did not recover protein synthesis in these cells. If antidote efficacy was ranked by reduced amounts of LDH leakage, only DMPS and BAL were effective antidotes in 11Lu cells. In L2 and A549 cells no significant effects were seen using this parameter. Our results do not agree well with in vivo data on zinc poisoning in mice (EDTA > dPA > DMPS); both series of antidote efficacy do not correlate with tabulated stability constants of binary complexes (dPA > EDTA > BAL > HIS > NAC). We conclude that orders of antidote efficiency obtained from in vivo systems might be extremely variable for each test system. Theoretically obtained data (as complex building constants for chelating compounds as metal antidotes) do not necessarily consider pharmacokinetic properties. J. Trace Elem. Exp. Med. 13:215–226, 2000. © 2000 Wiley-Liss, Inc.

Chemometric investigation of complex equilibria in the solution phase. 3. Chemical models for the complexation of nickel(II) with adipic acid dihydrazide and 2-furoic acid hydrazide in water-N,N'-dimethylformamide and water-dioxane media. Correlation with solvent parameters

The stability constants of binary complexes of adipic acid dihydrazide or 2-furoic acid hydrazide with Ni(II) in water N,N'-dimethylformamide or water-dioxane (10-60% (vol/vol)) were determined pH metrically. The titrand consists of the mineral acid, ligand, and metal ion solutions in water-cosolvent mixtures. The hydrogen ion activities were measured using sodium hydroxide as titrant.

Multinuclear NMR and potentiometric studies on the interaction of zinc and cadmium with cytidine and glycylglycine. The effect of the anion

The stability constants for binary complexes formed between Zn 2+ and Cd 2+ with cytidine and glycylglycine and for the ternary complexes with the same ligands were determined by spectroscopic ( 1H and 13C NMR) and, except those involving Zn 2+ and cytidine, by potentiometric pH titrations in aqueous solution. The calculated values show that cadmium binds much more strongly to cytidine than zinc, and that a small but significant increase in the stability of zinc/cytidine interaction, but not for cadmium/cytidine, is observed in the presence of glycylglycine. The chemical shifts observed for cytidine with zinc show a marked dependence on the anion, being much larger for the chloride salt than for the nitrate and increase upon addition of glycylglycine, although the calculated stability constants are identical for both salts. Finally, the choice of reference chemical shifts used in the spectroscopic titrations and the effect of charged species on the values of the acidity constants are discussed.

Complexes binaires du nickel(II) et du zinc(II) avec la 1-canavanine et la 1-arginine, études potentiométriques et spectroscopiques

The stability constants of binary complexes of 1-canavanine (Can) and 1-arginine (Arg) with Ni2+ and Zn2+ have been calculated at 25 °C and at ionic strength μ = 0.1 (NaNO3). This technique is completed with spectrophotometry and circular dichroïsm measurements in the ultraviolet and visible ranges. Thus we determined the molar absorbances and the molar circular dichroïsm of ligands and complexes with Ni2+ and Zn2+. Concerning the nickel(II), these measurements display three complexes, NiL, NiL2, and NiL3. 1-Canavanine, which generally has a tridentate ligand behaviour, becomes a bidentate ligand in the Ni(Can)3 complex. With regard to zinc(II), this study only displays the ZnL and ZnL2 species. Key words: 1-arginine, 1-canavanine, circular dichroïsm, nickel binary coordination, zinc binary coordination.

Determination of stability constants from linear-scan or cyclic-voltammetric data using a non-linear least-squares method

Stability constants of binary complexes can be determined using linear-scan or cyclic-voltammetric data. In contrast to a recently applied graphical method, numerical treatment based on a non-linear least-squares refinement allows one to make optimal use of the information contained in the data set. This is illustrated by re-evaluating recent literature data.

Ternary complexes of xanthosine in solution

Stability constants, of the mixed ligand complexes (1:1:1) containing metal-xanthosine (1:1) [M = Cu(II), Ni(II), Zn(II), Co(II), Mn(II), Mg(II), and Ca(II)] complexes and secondary ligands. N,N-tetramethylethylenediamine (TMEN), α,α′-bipyridyl (bipy), 1-10-phenanthroline ( O-Phen) and 5 sulfosalicylic acid (SSA) or metal-xanthosine in a 1:2 ratio, have been determined potentiometrically at 45±0.1°C and 0.10 M (KNO 3) ionic strength. The stability constants of these metal ternary complexes and 1:2 metal-xanthosine complexes are found to be higher than the corresponding stability constants of binary complexes. Thus the positive values of Δ log K (defined as the difference in the overall 1:1:1 stability constants and corresponding 1:1 binary complexes) may be due to the “stacking” interaction of the ligands concerned.

Stability Constants of Binary Complexes of Lanthanons with Thiotropolone

Stability Constants of Binary Complexes of Lanthanons with Thiotropolone