Search

Abstract: Solution equilibrium studies on the Cu(II)–polyamine–methionine ternary systems (polyamine: ethylenediamine (en), diethylenetriamine (dien), N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (Me5dien)) have been performed by pH-potentiometry, UV–Vis spectrophotometry and EPR methods. The obtained results suggest the formation of the mixed-ligand complexes with [Cu(A)(Met)]+ stoichiometry in all studied systems. Our spectroscopic results indicate the tetragonal geometry for [Cu(en)(Met)]+, the geometry slightly deviated from square pyramidal for [Cu(dien)(Met)]+ and strongly deviated from square pyramidal towards trigonal bipyramidal for the [Cu(Me5dien)(Met)]+ species. The coordination modes in these mixed-ligand complexes are discussed. [Copyright &y& Elsevier]

Abstract: Solution equilibrium studies on the Cu(II)–polyamine–histidine ternary systems (polyamine: ethylenediamine (en), diethylenetriamine (dien), N,N,N′,N″,N″-pentamethyldiethylenetriamine (Me5dien)) have been performed by pH-potentiometry, UV–Vis spectrophotometry and EPR methods. The obtained results suggest the formation of the mixed-ligand complexes with [Cu(A)(His)]+ stoichiometry in all studied systems. Additionally, in the systems with dien and Me5dien protonated [Cu(A)(H–His)]2+ species also exists in acid solution. Our spectroscopic results indicate the tetragonal geometry for the [Cu(en)(His)]+, the geometry slightly deviated from square pyramidal for the [Cu(dien)(His)]+ and strongly deviated from square pyramidal towards trigonal bipyramidal for the [Cu(Me5dien)(His)]+ species. The coordination modes in these mixed-ligand complexes are discussed. [Copyright &y& Elsevier]

Abstract: The stability constants and coordination modes of the mixed-ligand complexes formed by copper(II) ion and ethylenediamine as a primary ligand and methioninehydroxamic acid (Metha) or histidinehydroxamic acid (Hisha) as a secondary ligand L were determined by potentiometric titration, UV–Vis and EPR spectroscopy. The obtained results suggest the formation of mixed-ligand species in basic solution with 4N coordination – both amine and hydroxamic nitrogens of Metha or Hisha (NH2, Nha) and two amine nitrogens of en (2×NH2) in the equatorial plane. [Copyright &y& Elsevier]