The superoxide dismutase (SOD) mimetic were synthesized by complexation of manganese(II) with 1,5- diphthalimido-3-azapentane and ethylene diamine at molar ratios of 1:1:1 (compound 1) and 1:2:2 (compound 2). Their activities were evaluated by measuring inhibition of the photoreduction of nitro blue tetrazolium. Results revealed that both complexes possessed interesting SOD activity (IC50) of 0.16 and 0.09 μM for compounds 1 and 2, respectively. Molecular modeling and quantum chemical calculation of the phthalidimide-based complex was also performed to elucidate the correlation of electrostatic charge of transition metal ions with the SOD activity.