Important Secondary Ligand Research Articles

Ternary Complexes Formed Among Pd(II) Ions, Nucleobases, Nucleosides, Nucleotides and Some Biologically Important Compounds

Potentiometric measurements have been performed at (25.0 ± 0.1) °C and ionic strength I = 0.1 mol·L−1 KNO3 for the interaction of guanine, thymine, uracil, aminouracil, guanosine, inosine, cytidine, guanosine 5′-monophosphate, adenosine 5′-diphosphate, adenosine 5′-triphosphate and palladium Pd(II) with the biologically important secondary ligands glycine, leucine, N,N-bis(2-hydroxyethyl) glycine, N-[tris(hydroxymethyl)methyl] glycine, d-2-t-butylglycine and Boc-N-methyl-l-leucine. The formation of various 1:1:1 ternary complexes and 1:1:2 quaternary complex species as well as the polynuclear species was inferred from the potentiometric pH-titration curves. The experimental conditions were selected such that self-association of the nucleobases, nucleosides or nucleotides and their complexes due to stacking interaction is negligibly small; that is, the normal monomeric protonated ternary complexes were studied. Formation of the ternary complexes of some systems was confirmed using cyclic voltammetry, differential pulse voltammetry and conductance measurements in solution.

Metal Ion Complexes Containing Dipeptides, Tripeptides, and Biologically Important Zwitterionic Buffers

Potentiometric equilibrium measurements have been performed at (25.0 ± 0.1) °C and ionic strength I = 0.1 mol·dm-3 KNO3 for the interaction of glycylglycine, glycylhistidine, glycylglycylglycine, glycylhistidylglycine, and Al(III), Ga(III), In(III), and Tl(I) with the biologically important secondary ligands bicine [N,N-bis(2-hydroxyethyl)glycine], tricine [N,N,N-tris(hydroxymethyl)methylglycine], PIPES [piperazine-1,4-bis(2-ethanesulfonic acid)], HEPES (N-[2-hydroxyethyl]piperazine-N-[2-ethanesulfonic acid]), and EPPS 4-(2-hydroxyethyl)piperazine 1-propanesulfonic acid in a 1:1:1 ratio. Ternary complexes of the type Al(III)−glycylglycine−guanosine, Al(III)−glycylglycine−guanosine 5‘-monophosphate (GMP), Al(III)−glycylglycylglycine−guanosine, Al(III)−glycylglycylglycine−GMP, Al(III)−glycylhistidine−guanosine, Al(III)−glycylhistidine−GMP, Al(III)−glycylhistidylglycine−guanosine, Al(III)−glycylhistidylglycine−GMP in a 1:1:1 ratio have been investigated. The experimental conditions were selected such that se...

Ternary Complexes Formed by Trivalent Lanthanide Ions, Nucleotides, and Biological Buffers

Potentiometric equilibrium measurements have been performed at (25.0 ± 0.1) °C and ionic strength I = 0.1 mol dm-3 KNO3 for the interaction of adenosine 5‘-monophosphate, guanosine 5‘-monophosphate, cytidine 5‘-monophosphate, and La(III), Ce(III), Pr(III), and Eu(III) with the biologically important secondary ligand zwitterionic buffers (3-[N-morpholinol])-2-hydroxypropanesulfonic acid, 2-(N-morpholino)ethanesulfonic acid, N-2-acetamido-2-aminoethanesulfonic acid, and N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid. Measurements were made in a 1:1:1 ratio. Formation constants for the monohydroxy, dihydroxy, and dimeric ligand complexes for the binary systems Ln(III) + adenosine 5‘-monophosphate, Ln(III) + guanosine 5‘-monophosphate, Ln(III) + cytidine 5‘-monophosphate, and Ln(III) + zwitterionic buffers have been evaluated. The formation of various 1:1:1 normal and protonated mixed ligand complex species was inferred from the potentiometric pH-titration curves. The experimental conditions were selected...

Role of Biologically Important Zwitterionic Buffer Secondary Ligands on the Stability of the Mixed-Ligand Complexes of Divalent Metal Ions and Adenosine 5‘-Mono-, 5‘-Di-, and 5‘-Triphosphate

Potentiometric equilibrium measurements have been performed at (25.0 ± 0.1) °C and ionic strength I = 0.1 mol dm-3 KNO3 for the interaction of the purine nucleotides adenosine 5‘-mono, 5‘-di, and 5‘-triphosphate and Cu(II), Co(II), Ni(II), Mn(II), Zn(II), Ca(II), and Mg(II) with the biologically important secondary ligand zwitterionic buffers 3-(N-morpholino)propanesulfonic acid, 3-[(1,1-dimethyl-2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid, N-(2-hydroxyethyl)piperazine-N‘-2-hydroxypropanesulfonic acid, piperazine-N,N‘-bis(2-ethanesulfonic acid), and piperazine-N,N‘-bis(2-hydroxypropanesulfonic acid) in a 1:1:1 ratio and the formation of various 1:1:1 normal and protonated mixed-ligand complex species was inferred from the potentiometric pH titration curves. The experimental conditions were selected such that self-association of the purine nucleotides and their complexes was negligibly small; i.e., the monomeric normal and protonated ternary complexes were studied. Initial estimates of the formatio...

Potentiometric Studies on the Binary and Ternary Complexes of Copper(II) Containing Dipicolinic Acid and Amino Acids

The binary and ternary complexes of Cu(II) with dipicolinic acid as a primary ligand and some selected mono- and dicarboxylic amino acids as biologically important secondary ligands were studied potentiometrically. The acidity constants of the ligands were measured and used for determining the stability constants of the complexes formed in aqueous solutions at different temperatures at an ionic strength of 0.1 mol dm-3 NaNO3. The formation of 1:1:1 ternary complexes is inferred from the potentiometric titration curves. The order of stability of the binary or ternary complexes in terms of the nature of the amino acid is investigated and discussed. The values of Δ log K for the binary and ternary complexes involving amino acids have been evaluated along with the thermodynamic parameters ΔH°, ΔS°, and ΔG°.

Potentiometric and conductometric studies on the binary and mixed ligand complexes in solution: MII-dipicolinic acid–glycine systems

The binary and mixed ligand complexes of some alkaline earth and transition metal (II) ions with dipicolinic acid (DPA) as a primary ligand and the biologically important secondary ligand (glycine), were studied using potentiometric technique. The acidity constants of the ligands were determined and used for determining the stability constants of the complexes formed in aqueous solutions under the experimental conditions (t=25°C, μ=0.1 M NaNO3 ). The dissociation constants of DPA were also determined in various water+dioxane mixtures under the same experimental conditions. It is concluded that a pronounced change in the pK values is observed as the solvent is enriched in dioxane. The values of ΔlogK have been evaluated and discussed. In addition, the chelation mode of ternary complexes was ascertained by conductivity measurements.

Potentiometrische Untersuchung der Bildungsgleichgewichte von bin�ren und tern�ren Komplexen von Kobalt(II) mit Adenosin-5?-mono-, -di- und -triphosphat und einigen biologisch bedeutenden polybasischen Sauerstoffs�uren

Potentiometric equilibrium measurements have been made for the interaction of adenosine-5′-mono-,-di-, and -triphosphate, and Co(II) with biologically important secondary ligands (malic, maleic, succinic, tartaric, citric, and oxalic acid). The formation of various 1:1:1 mixed ligand complexes inferred from the potentiometric titration curves. Initial estimates of the formation constants of the resulting species and the acid dissociation constants ofAMP,ADP,ATP and the secondary ligand acids have been refined with a computer program. In some systems, the ternary complexes are found to be more stable than the corresponding binary ones. In some ternary systems studied, interligand interactions or some cooperativity between the coordinate ligands, possibly H bond formation, have been found to be most effective in deciding the stability of the complexes formed in solution. Stabilities of mixed ligand complexes increase in the orderAMP maleic > tartaric > malic > citric > oxalic acid.

Tern�re Komplexe in L�sung. Vergleich der Koordinationstendenz einiger biologisch wichtiger zwitterionischer Puffer an bin�re Komplexe von Cu(II) und Adenosin-5?-mono-, -5?-di- und-5?-triphosphat

Potentiometric equilibrium measurements have been made at 25.0±0.1 °C and ionic strengthI=0.1 mol dm−3 KNO3 for the interaction of adenosine 5′-mono-, 5′-di-, and 5′-triphosphate (AMP,ADP andATP) and Cu(II) with biologically important secondary ligand zwitterionic buffers (N,N-bis-(2-hydroxyethyl)-2-aminoethanesulphonic acid (BES), N-tris-(hydroxymethyl)-methyl-2-aminoethanesulphonic acid (TES), N,N-bis-(2-hydroxyethyl)-glycine (Bicine) andtris-(hydroxymethyl)-methylaminopropane sulphonic acid (TAPS)) in a 1:1:1 ratio and the formation of various 1:1:1 mixed ligand complex species inferred from the potentiometricpH titration curves. Initial estimates of the formation constants of the resulting species and the acid dissociation constants ofAMP,ADP,ATP, and secondary ligands have been refined with the SUPERQUAD computer program. Negative and positive Δ logK values were obtained for the ternary systems studied. In some Cu(II) ternary systems studied the interligand interactions or some cooperativity between the coordinate ligands, possibly H bond formation, has been found to be most effective in deciding the stability of the ternary complexes formed in solution. Stabilities of mixed ligand complexes increase in the orderAMP Bicine>TES>BES.

Ternary complexes in solution. Comparison of the coordination tendency of some polybasic oxygen acids toward the binary complexes of copper(II) and adenosine 5'-mono-, 5'-di-, and 5'-triphosphate

Potentiometric equilibrium measurements have been made at (25±0.1) o C and ionic strength I=0.1 mol dm -3 KNO 3 for the interaction of adenosine 5' mono-, 5'-di-, and 5'-triphosphate (AMP, ADP, and ATP) and Cu(II) with biologically important secondary ligand acids (malic, maleic, succinic, tartaric, and oxalic acids) in a 1:1:1 ratio and the formation of various 1:1:1 mixed ligand complex species inferred from the potentiometric pH titration curves. Initial estimates of the formation constants of the resulting species and the acid dissociation constants of AMP, ADP, ATP, and secondary ligand acid have been refined with the SUPERQUAD computer program

Ternary complexes of nickel(II) withAMP,ADP andATP as primary ligands and some biologically important polybasic oxygen acids as secondary ligands

Potentiometric equilibrium measurements have been made at 25±0.1 °C (μ=0.1 mol dm−3 KNO3) for the interaction of adenosine-5′-mono-, -di-, and-triphosphate (AMP,ADP, andATP) and Ni(II) with biologically important secondary ligand acids (malic, maleic, succinic, tartaric, citric and oxalic acids) in a 1:1:1 ratio and the formation of various 1:1:1 mixed ligand complex species inferred from the potentiometricpH titration curves. Initial estimates of the formation constants of the resulting species and the acid dissociation constants ofAMP,ADP,ATP and secondary ligand acid, have been refined with SUPERQUAD computer program. In some systems Δ logK values are positive, i.e. the ternary complexes are found to be more stable than the corresponding binary complexes. H-bond formation seems to be most effective in deciding the stability of the ternary complexes formed in solution. Stabilities of mixed ligand complexes increases in the orderAMP maleic>tartaric>malic>citric>oxalic acid.

Ternary complexes in solution. Comparison of the coordination tendency of some polybasic oxygen acids toward the binary complexes of Cu(II) andAMP,ADP orATP

Potentiometric equilibrium measurements have been made at 25±0.1°C (μ=0.1 mol dm−3 KNO3) for the interaction of adenosine-5′-mono-, -di- and -triphosphate (AMP,ADP andATP) and Cu(II) with biologically important secondary ligand acids (malic, maleic, succinic, tartaric, citric and oxalic acids) in a 1:1:1 ratio and the formation of various 1:1:1 mixed ligand complex species inferred from the potentiometricpH titration curves. Initial estimates of the formation constants of the resulting species and the acid dissociation constants ofAMP,ADP,ATP, and secondary ligand acid, have been refined with the SUPERQUAD computer program. In some systems ΔlogK values are positive, i.e. the ternary complexes are found to be more stable than the corresponding binary complexes. In some Cu(II) ternary systems the interligand interactions between the coordinate ligands, possibly H bond formation, have been found to be most effective in deciding the stability of the ternary complexes formed in solution. Stabilities of mixed ligand complexes increase in the orderAMP maleic > tartaric > malic > citric > oxalic acid.

Potentiometric studies on the mixed ligand complexes in solution: M II-tetracycline-glycine systems

The interaction of Be, Mg, Ca, Sr and Ba ions with tetracycline was followed by pH-metry and stability constants were determined for the chelates containing 1 : 1 ratio of ligand to metal ion at t = 25°C and μ = 0.1 mol dm −3 (NaNO 3), for the above mentioned metals except Be where 1 : 1 and 2 : 1 complexes were detected. The protonation constants of tetracycline were also determined under the same conditions. The stability constants of the 1 : 1 complexes formed decrease in the order Be > Mg > Ca > Sr > Ba. Potentiometric equilibrium measurements have been made under the same conditions for the interaction of tetracycline and Be, Mg, Ca, Sr, Ba, Cu and Zn with the biologically important secondary ligand (glycine) in a (1 : 1 : 1) ratio. The Δlog K values [Δlog K = log k M(TC) M(TC)(gly) − log K M M(gly)] were interpreted on the basis of statistical considerations and the nature of species formed in solution.

Interaction of rare earth metal ions with nucleosides—a study of binary and ternary systems in solution

Studies on interaction of La(III), Pr(III), Nd(III), Sm(III), Gd(III), Dy(III) and Er(III) with inosine and xanthosine in a 1:1 ratio have been carried out by potentiometric equilibrium measurements at 35±0·1°C and 0·1 M (KNO3) ionic strength. Investigations were also made for the interaction of these metal ions and nucleosides with the biologically important secondary ligands glycine and histidine. These investigations were undertaken with a view to assess the influence of charge on the structure and stability of 1:1 metal-inosine/xanthosine systems.

Ternary complexes of 5′-cytidine monophosphate and cytosine with some biologically important secondary ligands

Potentiometric equilibrium measurements have been made at 35°C for the interaction of 5′-cytidine monophosphate and Cu(II), Ni(II), Zn(II), Co(II), Mn(II), Mg(II) and Ca(II) with biologically important secondary ligands (glycine, oxalic cid, histidine and histamine) in a 1:1:1 ratio. Similar studies with cytosine were carried out for comparison. For the above systems, the ternary complexes are found to be more stable than the corresponding binary complexes. The Δ log K values for 1 : 1 : 1 complexes of metal-5′-cytidine monophosphate (or cytosine) with aromatic ligands are more positive compared to the corresponding complexes with aliphatic ligands. This is explained in terms of “stacking phenomenon” that occur between the two aromatic moieties of the primary and secondary ligands in solution.