Measurements of thermodynamic parameters for complexation between a tetra-aza macrocycle ligand and some metal cations based on conductometric method

Thermodynamic aspects of complexation process between 14-membered tetra-aza macrocycle ligand and four metal cations were studied in ethanol–water (EtOH–H2O) binary mixtures at different temperatures by applying conductometric method. In all the cases, the stability constants (log Kf) of 1:1 formed complexes between ligand and cations were obtained by fitting the molar conductivity curves using the Genplot computer program and the formation constant values (log Kf  ) were generally in the range of 1.41–2.70. The values of thermodynamic parameters, standard enthalpy (ΔHC∘) and standard entropy (ΔSC∘) were obtained from the temperature dependence of the stability constants using the Van’t Hoff plots. Complexes in every cases were found to be entropy stabilized, and the selectivity order of all the complexes changes as well as the changes in composition of the solvent mixtures. The experimental data was tested by using artificial neural network (ANN) technique and was in a good agreement with estimated data.