Two organic ligands containing pyridine ring and three of their cobalt and nickel complexes were prepared and recrystallized from their appropriate solvents. Careful courses of infrared absorption measurements before and after various gamma radiation doses (105–109rd), elemental analysis and melting point determination were conducted. Materials investigated were arranged in a descending order of their decreasing stability towards gamma irradiation. Results were further discussed in terms of bond-strength and the steric effect of molecular groups.