Solution state studies on thermodynamic parameters and complexation behavior of inner transition metal ions with creatinine in aqueous and mixed equilibria


Department of Chemistry, Hemchandracharya, North Gujarat University, Patan-384 265, Gujarat, India


The determination of formation constants of binary inner transition metal complexes where M
=Y(III) or La(III) or Ce(III) or Pr(III) or Nd(III) or Sm (III) or Gd (III) or Dy (III) or Th(IV) and
L = Creatinine have been carried out using Irving–Rossotti titration technique in aqueous media
at different temperatures and at ionic strength. To understand more about the nature of
equilibrium involving inner transition metals with Creatinine, the effect of dielectric constants on
the stability of these complexes at different percentage of solvent variation and at different
solvent systems has been studied. The formation constant (logβn) have been calculated on IBM
computer using BEST Program. Thermodynamic parameters (ΔG, ΔH and ΔS) are also
evaluated, negative ΔG, ΔH and ΔS values indicate that complex formation is favorable at
ordinary temperatures. Species distribution curves of complexes have been plotted as function of
pH using Fortran IV program SPE PLOT to visualize the equilibria systems in pH range of 2-8
pH. The order of stability for metals is Y < La < Ce < Pr < Nd < Sm < Gd < Dy < Th. This order
can be explained on the basis of basicity of ligand, protonation of ligand, electronic
configuration of metal ions, size and ionic potential of tripositive ion, charge/size ratio of metal
ions and species distribution diagrams.


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