Investigation of Extent of Interaction of Thiobarbituric Acid and Two Selected Amino Acids with Three Divalent Metal Ions in Aqueous-organic Medium at Different Temperatures
M. A. Oladipo
Department of Chemistry, Ladoke University of Technology, Ogbomoso, Oyo State, Nigeria.
K. T. Ishola *
Department of Chemistry, Federal College of Education (Special), Oyo, Oyo State, Nigeria.
T. A. Ajayeoba
Department of Chemistry, Obafemi Awolowo University, Ile-ife, Osun State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
The formation constants of binary and ternary complexes of Thiobarbituric acid as primary ligand and L-tyrosine and L-histidine as secondary ligands have been examined in 40% (v/v) ethanol-water mixture at 27oC and 35oC and at ionic strength of 0.02 NaNO3 by potentiometric method. The ligands formed 1:1 binary complexes with the metal ions. The primary and secondary ligands simultaneously coordinated to the metal ions to form 1:1:1 ternary complexes. The difference in stability constants of binary and ternary complexes were determined by △logK and RS%. Ternary complexes exhibited enhanced stability than the binary complexes. The stability of the complexes decrease with increase in temperature. The thermodynamic parameters such as Gibb’s free energy change (ΔG), entropy change (ΔS) and enthalpy change (ΔH) accompany the interactions were evaluated. The interactions were found to be spontaneous, exothermic, and entropically favoured.
Keywords: Stability constants, ternary complexes, binary complexes, thermodynamic parameters