Studies in amine-amino acid mixed ligand chelates—I

Chemistry Department, Faculty of Science, M.S. University of Baroda, Baroda-2, India
Journal of Inorganic and Nuclear Chemistry 01/1970; 32(10):3271-3275. DOI: 10.1016/0022-1902(70)80210-X

ABSTRACT Irving-Rossotti technique has been applied to study the formation constant of the reaction (Cu A)2+ + L− ⇌ (Cu AL)+ where A = dipyridyl and L = Glycine, α or β-alanine. Copper dipyridyl 1 : 1 is known to form at lower pH and is stable at higher pH when the secondary ligand gets bound. The values of the formation constant obtained in the mixed ligand systems are little less than the first formation constant of Cu-amino acid simple systems.

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    ABSTRACT: Stability constants of the ternary complexes [CuAL] whereA = 5-Nitro-1,10-phenanthroline, bis(2-pyridyl) ketone (DPK) orbis(2-pyridyl)amine (DPA) andL is the dianion of catechol, tiron, protocatechic acid, pyrogallol, 1,8-dihydroxynaphthalene, catecholaldehyde, 2,3-dihydroxynaphthalene, dopamine or adrenaline have been determined by potentiometric titration in dioxane water (1:1 v/v) medium using a SCOGS computer programme. The observed trend of stability is explained on the basis of the nature of substitution over the ligands, chelate ring size and also the composition of mixed solvent in case of DPK. Structural changes in DPK have also been discussed as a function of pH, composition of medium and coordinating mode of the secondary ligand in the ternary complexes.
    Journal of Chemical Sciences. 01/1986; 97(5):529-534.
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    ABSTRACT: Formation contants (log K MALMA) of mixed ligand complexes MAL, where M = UO 22+ or Th4+, A = IMDA, NTA, HEDTA, EDTA, CDTA or DTPA, and L = resorcinol (res), 2-methyl resorcinol (2-Me-res), 5-methyl resorcinol (5-Me-res) or 4-chloro resorcinol (4-Cl-res), have been determined pH-metrically by the Irving-Rossotti approach at 25°C and at an ionic strength,I = 0.2(moldm−3KNO3). The observed stability sequences are IMDA > NTA > HEDTA > EDTA > CDTA > DTPA, and 4-Cl-res > 5-Me-res > 2-Me-res > res with respect to primary and secondary ligands, respectively. Th4+ forms more stable mixed complexes than UO 22+. The A ΔlogK values are negative due mainly to the charge repulsion involved in the complexation MA + L⇋MAL.
    Journal of Chemical Sciences 02/1991; 103(2). · 1.18 Impact Factor
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    ABSTRACT: Spectrophotometric and pH-metric studies of the aqueous binary and mixed ligand complexes of Pb(II), Cd(II), Al(III) and Cu(II) were carried out with ascorbic acid and paracetamol. The study was conducted at an ionic strength of 0.15 mol dm-3 and a temperature of 37.0 ± 0.2 oC. The protonation constants of the free ligands and the stability constants of the binary and mixed ligand complexes were determined using pH titration data. Proton dissociation of free ligands and complex formation were also qualitatively confirmed with UV data. The stabilities of mixed ligand complexes were quantitatively compared with those of the corresponding single ligand complexes in terms of Δlog K. Aluminium formed the most stable binary complex; Al (paracetamol)2, with a high overall stability constant (log β2 = 16.74). The stable mixed ligand complexes; Pb (ascorbic acid) (paracetamol), Cd (ascorbic acid)(paracetamol) and Cu (ascorbic acid) (paracetamol) were observed with positive Δlog K values showing the ability of using them in less harmful chelation therapy of these metals. Further, the results revealed that the bioavailability of both ligands will be lower for a metal intoxicated person.
    Journal of the National Science Foundation of Sri Lanka 09/2013; 41(4):337-344. · 0.15 Impact Factor