The mechanism of reduction of the hydrogen peroxide by glutathione peroxidase mimic (GPx) were investigated by density functional theory (DFT) method at the M06-2X/6-31+G(d,p) level of theory. Thermodynamic and kinetic characteristics of the oxygen transfer from hydrogen peroxide molecule to selenium center in the GPx mimic were calculated for the related processes. Reduction reaction of H2O2 in the presence of GPx mimic was examined in different solvents, such as water, dimethyl sulfoxide (DMSO), methanol and chloroform. Based on the obtained results, the activation Gibbs energies of the reduction of H2O2 by GPx mimic in these solvents are 31.63 , 31.69 , 31.76 and 31.77 kcal.mol-1, respectively. Also, the rate constants (k) of the hydrogen peroxide reduction in the presence of GPx mimic were calculated using the conventional transition state theory (TST), which are 6.47×106 , 6.45×106 , 6.44×106 and 6.41×106 s-1 , respectively. Finally, the GPx mimic due to structural stability and best performance in various solvents as a candidate, has widespread applications in the fields of green chemistry, medicine and food industry.

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