• Y Laxmi Kumari

      Articles written in Journal of Chemical Sciences

    • Equilibrium studies on binary and ternary Cu(II) complexes containing ethylenediaminediacetic acid and a series of O-O, N-O and N-N donor ligands

      D Srinivasa Yogi G Narendra Kumar M Srinivas Mohan Y Laxmi Kumari

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      The formation constants for ternary metal complexes (MLA) where L = ethylenediaminediacetic acid (EDDA), M = Cu(II) and A = glycine, alanine, leucine, serine, threonine, methionine, proline, phenylalanine, tryptophan, histidine, aspartic acid, ethylenediamine, histamine, 2,2′-bipyridyl, 1,10-phenanthroline, imidazole, oxalic acid, malonic acid, pyrocatechol and nitropyrocatechol have been investigated by pH-metric method at 35°C andμ = 0.2 M (KNO3). With respect to the donor atoms on ligand A, the stabilities of the ternary complexes increase in the order O-O < N-O≈N-N. The stabilities of the various ternary complexes decrease with the increasing number of carboxylate groups on the ligand in the order ethylenediamine (EN) < ethylenediamine monoacetic acid (EDMA) < EDDA. Various factors influencing the formation and stabilities of ternary complexes are discussed.

    • Ternary Cu(II) complexes involving N-(1-naphthyl)ethylenediamine, ethylenediamine (N-N donors) and a series of amino acids (N-O donors)

      P Venkataiah M Srinivas Mohan Y Laxmi Kumari

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      The dissociation constants for N-(l-naphthyl)ethylenediamine (NEN) and the formation constants for binary (ML) and ternary metal complexes (MLA), where M = Cu(II), L = alanine, phenylalanine, tryptophan, lysine, arginine, serine, threonine, aspartic acid or histidine and A = NEN or ethylenediamine (EN) have been determined by pH titrations and are reported at 35°C (gm = 0.2 M KNO3). The relative stability of the ternary complexes are discussed in terms of statistical effects and the nature of ligands in the coordination sphere of the metal ion.

    • Equilibrium studies on ternary Cu(II) complexes containing adenosine-5′-triphosphate

      P Venkataiah Y Laxmi Kumari M Srinivas Mohan Harinath B Bathina

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      Interaction of adenosine-5′-triphosphate (ATP) with a series of binary Cu(II) complexes (ML) (where L =o-phenanthroline (Phen), 5-nitrophenanthroline (NPhen), 5-methyl phenanthroline (MPhen), 2,9-dimethylphenanthroline (DPhen), 2,9-dimethyl-4,7-diphenylphenanthroline (DPhPhen), 2,2′-bipyridyl (Bipy), bis(imidazol-2-yl) methane (BIM), oxalic acid (Ox), glycine (Gly), alanine (Ala), valine (Val), phenylalanine (Phe), tryptophan (Trp), methionine (Met), histidine (His) or aspartic acid (Asp) to form ternary complexes (MLA) was investigated by a pH-metric technique and the formation constants were evaluated at 35.0°C and μ = 0.2 M (KNO3). The influence exerted by ligand L on the binding of ATP to Cu(II) was quantitatively assessed and ATP was found to bind more strongly when L = bidentate nitrogen donors, relatively less strongly when L = amino acids and least strongly when L = a bidentate oxygen donor. With respect to the nitrogen donor ligands the stability of the ternary complexes decreases in the order NPhen > Phen > Bipy > MPhen > DPhen > BIM ≈ DPhPhen, whereas in ternary complexes containing amino acids the stability decreases in the order: Phe ≈ Trp > Ala > Gly ≈ Val ≈ Met > His > Asp. The trends in the stability of the various complexes are discussed in terms of the nature of the metal ion and the two ligands in its coordination sphere.

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