Synthesis, Thermal Kinetic Analysis and DFT Calculations of Pyrazine and Pyridine Complexes of Copper(II) Thiocyanate

Abstract

Two NNN type ligands namely bis-2,6-(pyrazol-1-yl) pyridyne (pp) and bis-2,6-(3,5-dimethyl-pyrazol-1-yl) pyridyne (dmpp) were prepared by the use of 2,6-dichloropyridine, pyrazol and 3,5-dimethylpyrazol. Using these ligands with SCN co-ligand two mononuclear Cu(II) complexes were synthesized and characterized. The complexes were investigated by thermogravimetry (TG) and differential thermal analysis (DTA) and subjected to isothermal and nonisothermal kinetic analyses. TG and DTA results indicated that the complexes showed two distinctive degradation steps and the NNN type ligand was removed from the structure at temperatures above 300 °C. The activation energies of these complexes and same thermodynamic parameters of these thermal reactions have been calculated. The situation of d orbitals of Cu(II) ion, the electron densities of donor atoms of the ligands, natural bond orbital (NBO) analysis, the theoretical IR spectra and HOMO-LUMO energy levels computed by the use of DFT/B3LYP methods with 6-311G (d) basis set in Gaussian 09 software. These data were employed to enlighten the thermal degradation of the complexes prepared.