Computer based stability constants and absorption maximum values for the copper(II) ternary complexes containing L-cysteic acid and some selected ligands

879-886The present paper deals with the determination of stability constants for sixteen ternary systems viz. Cu(II)- L-cysteic acid (cya) (A)-L.-pbenylalanine (pha), dopamine (dopm), dopa, imidazole(Him), benzimidazole(Bimz), histamine(Hist), L- histidine(His), DL-2- aminobutyric acid(2aba), DL-3- aminobutyric acid(3aba), 4- aminobutyric acid (4aba), DL-4-amino-3-hydroxybutyric acidi( ahba), 1,2-diaminopropane( tp), 1,3- diaminopropane(tp), DL-2,3-diaminopropionic acid (dapa), DL-2,4- diaminobutyric acid (daba), and DL-ornithine (orn) (B). These systems have given rise to the formation of ternary complexes of the types CuAB, CuAB2, CuABH or CuABH2. Though dopa ligand binds Cu(II) in a mixed mode in its CuB complex, in the CuAB species, it binds in a pyrocatechol-like mode. In all other systems, the binding modes of the ligands A and B in the CuAB species are similar to their binding in their respective binary systems. In the CuABH2 species in the Cu(II)-cya-dopm and dopa systems, the two protons reside with the ɸ-phenolato oxygen atoms of the respective secondary ligands. The possible protonation sites in the other CuABH and CuABH2 ternary complexes in this study are discussed

Mixed ligand Cu(II) complexes containing <i>o</i>-vanillin-l-tryptophan Schiff base and heterocyclic nitrogen bases: synthesis, structural characterization, and biological properties

<div><p>[Cu(L)] (<b>1</b>) and mixed ligand copper(II) complexes [Cu(L)(A)] (<b>2</b> and <b>3</b>), where <b>L</b> is the Schiff base derived from <i>o</i>-vanillin and l-tryptophan and <b>A</b> is pyridine (<b>2</b>) and imidazole (<b>3</b>), were synthesized and characterized using conventional and spectral techniques. <b>2</b> was structurally characterized using single crystal X-ray crystallography showing that Cu(II) is coordinated through N₂O₂ donors in a square plane. The EPR spectra of the complexes in frozen solution support a square-based structure. Electrochemical behavior of the complexes has been studied by cyclic voltammetry. The DNA-binding properties of <b>L</b> and <b>1–3</b> with calf thymus DNA were investigated by spectral and kinetic methods. For all the complexes, the maximum value of binding constant (0.38 × 10⁶) was achieved with <b>3</b> by spectroscopic titration. The ability of compounds to break pUC19 DNA was checked by gel electrophoresis. The ligand and copper complexes exert cytotoxicity against MCF-7 cell line.</p></div