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Journal ArticleDOI

Mixed-ligand complex formation equilibria of Cu II with biguanide in presence of glycine as the auxiliary ligand

01 Sep 2006-Journal of Chemical Sciences (Springer India)-Vol. 118, Iss: 5, pp 411-418
Abstract: Equilibrium study on the mixed ligand complex formation of CuII with biguanide(Bg) and glycine (HG), indicated the formation of the complexes: Cu(Bg)2+, Cu(Bg) 2 2+ , Cu(Bg-H)(Bg)+, Cu(Bg-H)2, Cu(Bg)(OH)+, Cu(Bg-H)(OH); Cu(G)+, Cu(G)(OH), Cu(G)2; Cu(G)(Bg)+, Cu(G)(Bg-H); (G)Cu(Bg)Cu(G)2+, (G)Cu(Bg-H)Cu(G)+, and (G)Cu(Bg-2H)Cu(G). From the deprotonation constants of coordinated biguanide (Bg) in the complexes Cu(Bg)(OH)+, Cu(Bg-H)(Bg)+ and Cu(G)(Bg)+, the Lewis basicities of the coordinated ligand species (Bg-H)-, OH- and glycinate (G-) were found to be of the order: (Bg-H)-≫ OH- > G-. Bridging (N1-N4, N2-N5) tetradentate mode of coordination by biguanide species Bg, (Bg-H)- and (Bg2H)2- was indicated from the occurrence of biguanide-bridged dinuclear mixed ligand complexes (G)Cu(Bg)Cu(G)2+, (G)Cu(Bg-H)Cu(G)+, (G)Cu(Bg-2H)Cu(G) in the complexation equilibria.

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Citations
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Journal ArticleDOI
24 Jan 2014-Biochemistry
TL;DR: The results clearly show that the copper binding energies cannot alone be the cause of the biochemical differentiation between Metf and PDI, and conclude that other factors such as pKa values and hydrophilicity of the compounds play a crucial role in their cellular activity.

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Abstract: Metformin (Metf), the most commonly used type 2 diabetes drug, is known to affect the cellular housekeeping of copper. Recently, we discovered that the structurally closely related propanediimidamide (PDI) shows a cellular behavior different from that of Metf. Here we investigate the binding of these compounds to copper, to compare their binding strength. Furthermore, we take a closer look at the electronic properties of these compounds and their copper complexes such as molecular orbital interactions and electrostatic potential surfaces. Our results clearly show that the copper binding energies cannot alone be the cause of the biochemical differentiation between Metf and PDI. We conclude that other factors such as pKa values and hydrophilicity of the compounds play a crucial role in their cellular activity. Metf in contrast to PDI can occur as an anion in aqueous medium at moderate pH, forming much stronger complexes particularly with CuII ions, suggesting that biguanides but not PDI may induce easy oxid...

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40 citations


Journal ArticleDOI
Xueling Quan1, Rokon Uddin1, Arto Heiskanen1, Mattias Parmvi1  +5 moreInstitutions (2)
TL;DR: Results of a quantitative investigation of interactions between metformin and L-cysteine-copper complexes suggest that met formin could interact with biological copper, which plays a key role in mitochondrial function.

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Abstract: Study of the copper binding properties of metformin is important for revealing its mechanism of action as a first-line type-2 diabetes drug. A quantitative investigation of interactions between metformin and L-cysteine–copper complexes was performed. The results suggest that metformin could interact with biological copper, which plays a key role in mitochondrial function.

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20 citations


3


Journal Article
Abstract: The mixed ligand complexes of Mn(II),Fe(II ), Co(II),Ni(II),Cu(II), Zn(II) and Cd (II) with 1-nitroso-2-naphthol (C 10 H 7 NO 2 ), symbolized (NNPhH)] and amino acid L-phenylalanine ( C 9 H 10 NO 2 ) , symbolized ( phe H), were synthesized and characterized by: Melting points, Solubility, Molar conductivity. determination the percentage of the metal in the complexes by flame(AAS), Molecular weight determined by Rast’s Camphor method, susceptibility measurements, Spectroscopic Method [FT-IR and UV-Vis], And Program [Chem office– CS .Chem.– 3D pro 2006] was used for draw compounds . The results showed that the deprotonated two ligands acts as a bidentate ligand , ( phe - ) was coordinated to the metal ions through the oxygen of the carboxylic group and the nitrogen of the amine and the 1-nitroso-2-naphthol ligand was coordinated to the metal ions through the oxygen and nitrogen atoms. The electronic absorption spectra and magnetic susceptibility measurements of the complexes indicate octahedral geometry for all the complexes. Key words: phenyl alanine , amino acid) Complexes , 1-nitroso-2-naphthol ,mixed ligands and Antibacterial Activities

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10 citations


Journal ArticleDOI
Abstract: The study of the ternary interactions of some phenoxyacetic acids derived from a herbicide, with the heavy metals present in soil in trace amounts has been realized by potentiometric measurements. The stability constants of the ternary complexes have been calculated at 25°C and ionic strength 0.1(NaNO3). The experimental results have confirmed the presence of one ternary hydroxide species MH−1(2,4-D)(2,4-MCPA) for Cu(II), Pb(II) and Zn(II) on one hand and MH−2(2,4-D)(2,4-MCPA) for Hg(II) on the other. The order of stability constants has been found to be: Cu(II)>Hg(II)>Pb(N)>Zn(N)>Cd(N). Finally, a quantum approach has been achieved by the semi-empirical AM1 method for the mercuric complex.

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2 citations


Journal ArticleDOI
Abstract: Combined pH-metric and spectrophotometric investigations on the complex formation equilibria of CuII with guanylurea (H21NC(=O) 2NH.C(=3NH) 4NH2), hereafter, GuH, in the absence and in the presence of glycine (GlyH), in aqueous solution indicates variety of binary and mixed-ligand complexes: Cu(Gu)+, Cu(Gu)(OH); Cu(Gu)2, Cu(Gu-H)(Gu)−, Cu(Gu-H)22−, Cu(Gu-H)(Gu-2H)3−; Cu(Gly)+, Cu(Gly)(OH); Cu(Gly)(Gu); Cu(Gly)(Gu-H)−, Cu(Gly)(Gu-2H)2−; (Gly)Cu(Gu)Cu(Gly)+, (Gly)Cu(Gu-H)Cu(Gly) and (Gly)Cu(Gu-2H)Cu(Gly)−. At pH < 6, guanylurea anion (Gu−) acts as a [(C=O), 3N−] or [=]NH, 3N−] bidentate ligand and above pH 7 it is transformed through a coordination equilibrium into a (=1N−, =3N−) bidentate ligand, similar to biguanide dianion. Occurrence of dinuclear complex species, (Gly) Cu(Gu)Cu(Gly)+, in the complexation equilibria, indicates bridging double bidentate [(1NH2, 3N−), (C=O, 4NH2)] and/or [(1NH2, 4NH2), (C=O, 3N−)] chelation by Gu− ion in an isomeric equilibrium. Above pH 6·5, the dinuclear complex decomposes mostly to the mononuclear species, Cu(Gly)(OH) and Cu(Gu)(OH) and only partly deprotonates to (Gly)Cu(Gu-H)Cu(Gly) and (Gly)Cu(Gu-2H)Cu(Gly)−. Electronic spectral shifts, with change of pH have been correlated with the possible modes of coordination of guanylurea species.

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1 citations


References
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Book
01 Jan 1963-

3,177 citations



Journal ArticleDOI
H.M.N.H. Irving1, M.G. Miles1, L.D. Pettit1Institutions (1)
Abstract: Possible errors in the measurement of acid dissociation constants by potentiometric titration techniques have been considered, with particular references to nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic acid (EDTA). Unknown junction potentials can arise when pH measurements are carried out using a glass electrode with saturated calomel reference electrode which have been previously calibrated with a standard buffer solution. The magnitude of the influence of these unknown potentials has been demonstrated and an experimental procedure recommended which gives meaningful results. The precision of calculated acid dissociation constants will also be influenced by the presence of cationic species (e.g. H 4 L 4 ), the total acid strength, the absolute values of the constants and the value accepted for the auto-dissociation constant of water ( K w ). All these factors have been considered quantitatively and their effect on metal complex formation constants, calculated from these acid dissociation constants, noted. The proton dissociation constant of the cationic species of NTA (i.e. H 4 L + ) has been found to have the value of p K 0 =0.80 at 20° and μ=0.10 M .

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1,149 citations



Journal ArticleDOI
Sayce Ig1Institutions (1)
01 Dec 1968-Talanta
TL;DR: The program, which employs the non-linear least-squares method, may be used to calculate equilibrium constants for hydrolysed metal ions, protonated ligands, and simple, Protonated, Hydrolysed, polynuclear, and mixed complexes.

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Abstract: A general computer program is described for the interpretation of pH titration data for mixtures containing the ions of up to two metals and up to two ligands. The program, which employs the non-linear least-squares method, may be used to calculate equilibrium constants for hydrolysed metal ions, protonated ligands, and simple, protonated, hydrolysed, polynuclear, and mixed complexes.

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296 citations