Ternary Complexes of Copper(II) Containing 2,2'-Bipyridyl & Some Diaminocarboxylic Acids

717-71

Equilibrium Studies on Containing -Arginine & Copper(II) Mixed Ligand Complexes -Histidine, Histalnine or Imidazole

58-6

Ternary Complexes of Copper(II) Containing Some Similar Types of Amino Acids

990-99

Mixed ligand complexes of nickel(II) with imidazoles and some dipeptides

468-471The computer based analysis of the pH titration data in the Ni(II)-imidazole (him)/histamine (hist)/L-histidine(his) (A)glycyl-L-phenylalanine(glyphe), glycyl-L-tyrosine(glytyr) and L-tyrosylglycine (tyrgly) (B) systems shows the presence of NiAB, NiABH-1, NiA2B or NiAB2 mixed ligand species. The results demonstrate that him, hist and his(A) are respectively mono-, bi- and tri-dentate and the dipeptide(B) ligands are bidentate in NiAB, NiA2B and NiAB2 complexes. The amide deprotonated dipeptide (BH-1) appears to bind in a tridentate mode in the NiABH-1 species in the him(A) systems, while the trends in results clearly demonstrate the bidentate binding of (BH-1) in the hist/his(A) mixed ligand systems. &nbsp

Ternary complexes of nickel(II) involving 6-aminopenicillanic acid and some potentially bidentate or tridentate ligands

2088-2091Multiple equilibrium studies by pH-metric and visible spectral measurements in the ternary nickel(II) complexes with 6-aminopenicillanic acid (6apa) as ligand A and diamines [1,2- diaminopropane(dp), and 1,3-diaminopropane(tp)] and diaminocarboxylic acids [DL-2,3-diaminopropionic acid(dapa), DL-2,4- diaminobutyric acid(daba) and DL-2,5-diaminovaleric acid(dava)] as ligands B show the presence of NiABH2, NiABH or NiAB ternary complex species. The ligand, 6apa binds the metal ion via 6 amino and 7 carbonyl oxygen atoms in both the NiABH and NiAB species, and the binding of ligand B in NiAB complexes is exactly similar to their binding in the respective binary species. The results indicate the site of protonation in the NiABH species to be with the terminal amino group of the ligand B. In the NiABH2 complexes, one proton is attached to the ligand A and other to the ligand B. The computer simulated distribution of the complexes in solution has been evaluated

Potentiometric and spectral studies of the solution equilibria in Ni(II)-6- aminopenicillanic acid-imidazole containing ligand systems

575-578Stability constants of NiABH2, NiABH, NiAB or NiAB2 mixed ligand complexes in Ni(II)-6-arnmopenicilianic acid (6apa) (A)-imidazoles <span style="font-size:14.0pt;font-family:HiddenHorzOCR; mso-bidi-font-family:HiddenHorzOCR">[imidazole(him), benzimidazole(bim), histamine(hist) & L-histidine(his)] (B) systems are reported. The 6apa (A) ligand binds via 6-amino nitrogen and 7-carbonyl oxygen atoms in the NiAB and NiAB2 complexes and the size of the chelate ring formed by 6apa (A) explains higher stability for NiAB2 compared to that of NiAB. Both the stability constant and absorption maximum values for the NiAB species indicate respectively rnono-, bi- and tri-dentate binding of him, hist & his (B) ligands. The results indicate the site of protonation in NiABH species to be with A, while in NiABH2 species one proton is attached with A, and other with B.</span

Studies on Nickel(II)-Pyridoxamine-Imidazole Containing Mixed Ligand Complex Systems

ABSTRACT: The stability constants of species present in the systems Ni(II)-pyridoxamine(pym)(A) and Ni(II)-pyridoxamine(pym)(A)-imidazole containing ligands(B) [B = imidazole(him), benzimidazole(bim), histamine(hist) and L-histidine(his)] have been determined pH-metrically using the MINIQUAD computer program. The existence of the species NiAH, NiA and NiA 2 was proven for the Ni(II)-pym(A) system, whereas for the Ni(II)-pym(A)-B systems NiABH 2 , NiABH, NiAB and NiAB 2 species were identified. The pym ligand(A) binds the metal ion via its phenolic oxygen and amino methyl nitrogen atoms in the NiAB and NiAB 2 species, and the binding of ligand B in these complexes is similar to their binding in the respective binary species. The site of protonation in NiABH and NiABH 2 species is explained. A more positive ∆ log K values for NiAB compared to NiAB 2 species is discussed. The computer simulated distribution of the complexes in solution has been evaluated. The mixed ligand pyridoxamine complex of Ni(II) with L-histidine was prepared and characterized by conventional methods

pH-metric Investigation of Cu(II) Complexes with Dipeptides

672-67

Mixed-ligand complex formation by Cu(II) with imidazole and dipeptides

The species distribution and stability constants were evaluated for six mixed imidazole (A)-dipeptide (B) complexes of Cu(II) in aqueous perchlorate medium at I = 0.15 M (NaClO4) and 37 &#176;C from pH titration data. The dipeptides used are glycylglycine, glycyl-L-alanine, L-alanylglycine, glycyl-L-leucine, L-leucylglycine and glycinamide. In addition to the binary complex species CuA, CuA2, CuA3, CuA4, CuB, CuBH-1, CuB2H-1, three mixed complexes CuA2B, CuA2BH-1 and CuABH-1 were detected in each system. However in the glycinamide secondary ligand (B) system, the mixed species CuAB formed instead of CuABH-1. The stability order found for these complexes is discussed in terms of the steric effects due to side chain substituents in the dipeptide (B) ligands. The results suggest that mixed-coordination enhances the stability of the complexes. The amide deprotonated dipeptides (B) appear to be tridentate in the CuA2BH-1 and CuABH-1 complexes

Ternary Coordination Complex Formation between Glycylglycine, Copper(II) & <img src='http://www.niscair.res.in/jinfo/smaller.gif' border=0><img src='http://www.niscair.res.in/jinfo/small.gif' border=0>-4-Aminobutyric Acid

435-43