Study of thermodynamics and complex structures on spin transitions of [Fe2(Htrz)6(trz)3]Cl and [Fe4(Htrz)10(trz)5]Cl3 complexes using the Density Functional Theory method

The complex of iron(II) 1,2,4 H-triazole chloride is a complex that has spin transition characteristics. Thermodynamic studies and determination of changes in complex structured data have been carried out on the [Fe-2(Htrz)(6)(trz)(3)]Cl and [Fe-4(Htrz)(10)(trz)(5)]Cl-3 complexes with the DFT method. The iron(II) 1,2,4 H-triazole chloride complex has a polymeric structure, so in this study used a model with 2 and 4 Fe(II) ions. The computational chemistry study using a hybrid functional/basis set B3LYP/6-31G(d). The results obtained show the distance between the Fe(II) ions, the bond length of Fe-N, and the distance between the Fe(II) ions with Cl- in the [Fe-2(Htrz)(6)(trz)(3)]Cl complex at low spin states respectively 3.717 angstrom, 1.990 angstrom-2.049 angstrom, and 6.829 angstrom, while in the high spin state respectively 3.932 angstrom, 2.130 angstrom-2.360 angstrom and 7,050 angstrom. The distance between the Fe(II) ions, the bond length of Fe-N, and the distance between the Fe(II) ions with Cl- in the [Fe-4(Htrz)(10)(trz)(5)]Cl-3 complex at low spin states respectively 3.661 angstrom-3.681 angstrom, 1.960 angstrom-2.089 angstrom and 5.037 angstrom, while in the high spin state respectively 3.911 angstrom-3.946 angstrom, 2.092 angstrom-2.367 angstrom and 5.280 angstrom. Thermodynamic data in [Fe-2(Htrz)(6)(trz)(3)]Cl complex is Delta E=-24.38989kJ/Mol, Delta H=-24.3909kJ/Mol, Delta G=-47.9364kJ/Mol, and Delta S=0.0789kJ/Mol. Thermodynamic data of [Fe-4(Htrz)(10)(trz)5]Cl-3 complex is Delta E=-12.8564kJ/Mol, Delta H=-12.8564kJ/Mol, Delta G=-33.6445kJ/Mol, and Delta S=0.0697kJ/Mol. The structure and thermodynamic data are compatible with experimental measurement data in the laboratory.