Mixed-ligand complexes of copper(II) with 1, 10’-Phenanthroline and amino acids

Abstract

ABSTRACT The speciation of the ternary systems formed by copper(II), 1,10’-Phenanthroline (Phen) and the amino acids: Histidine (HHis, HL), Arginine (HArg, HL), Lysine (HLys, HL), Aspartic acid (H2Asp, H2L), Glutamic acid (H2Glu, H2L) and Tyrosine (H2Tyr, H2L) was studied by means of emf(H) electromotive force measurements in aqueous solution at 25°C using 1.0 mol.dm−3 KNO3 as the ionic medium. The data obtained through potentiometric measurements were analysed using the computer program generalised least-squares LETAGROP. The species distribution diagrams as a function of pH were briefly discussed. The stability of the ternary complexes was compared with the corresponding one of the binary complexes in terms of ∆log K and % R.S. Spectrophotometric studies, UV-vis absorption and circular dichroism (CD), were employed to analyse the coordination modes of the ligands, the adopted geometry, and the stability of the major ternary complexes present in solution