Stability and Structural Studies on Ni(II)–5-Fluorouracil Mixed Ligand Complex Systems

Abstract

Binary and mixed ligand species formation and their distribution in the 5-fluorouracil (5-FU; A) and Ni(II) system in the presence of amino acids (B), namely glycine (gly), l-alanine (ala), l-valine (val) and l-phenylalanine (phe), were studied potentiometrically at different temperatures and pHs. The computer assisted analysis illustrates the existence of MAB and MAB2 species, where 5-fluorouracil and amino acids act as bidentates to form stable metal chelates. The distribution of different chemical species with temperature and pH was also studied. In addition, the coordination environments in the MAB system were determined by spectrophotometric measurements. The binding nature of both 5-FU (A) and amino acids (B) in MAB species of the Ni(II)–5-FU–amino acid systems reveal tetra coordination to the central Ni(II) ion. The fifth and sixth positions in MAB complexes are occupied by solvent water molecules/perchlorate ions and thus form a stable hexa coordinated environment. The calculated stabilization parameters indicate that the formed mixed ligand species have higher stabilities than their corresponding binary systems. Thermodynamic parameters were determined from the temperature dependent stability constant values. The mixed ligand complex systems show remarkable in vitro antimicrobial, antioxidant and nuclease activities.