Theoretical thermodynamic study on the interaction between Fe2+ ion and Pyrazole

The interaction of Fe2+ ion with Pyrazole was theoretically studied by Gussian 03, software at HF/(LanL2DZ+6-31G) and HF/ (LanL2DZ+6-31G (d)) levels in gas phase and solution. In this study acompartion between optimized structures of Pyrazole molecule in aspect of thermodynamicparameters such as enthalpy (H°), Gibbs free energy (G°) and entropy (S°) in presence of metallic ion(Fe2+), was performed. Thermodynamically analysis indicate that the relative enthalpy (H°) and Gibbsfree energy (G°) are negative values but entropy (S°) is positive value for Pyrazole-Fe2+ complex,suggesting thermodynamic favorability for covalent attachment of Pyrazole into Fe2+ ion. Also, theresults show with increasing dielectric constant of solvent the stability of Pyrazole –Fe2+ complexincreases