Determination of stability constants of ternary copper(II) complexes formed with picolinic acid and several amino acids

Abstract

ABSTRACTIn this work, the formation of ternary complexes with their respective formation constants in the systems formed by copper (II), picolinic acid and the amino acids = histidine (His), aspartic acid (HGly), proline (HPro), α-alanine (HαAla), β-alanine (HβAla), serine (HSer), threonine (HThr), phenylalanine (HPhe) and methionine (HMet)) was detected. The analysis involves the use of the potentiometric data with the least-squares program LETAGROP in aqueous solution at 25°C in 1M KNO3 solution. The relative stability of the ternary complexes was compared with the binary ones considering the values of Δlog K and log χ. Subsequently using the formation constants, the species distribution diagrams were generated and are briefly discussed here. The Cu (II)–picolinic acid–glutamic acid, Cu (II)–picolinic acid–serine and Cu (II)–picolinic acid–histidine systems were characterised by UV–Vis molecular absorption spectroscopy and cyclic voltammetry, obtaining results that confirm the formation of ternary complexes with octahedral geometry.