The bioorganometallic compounds 2-cyrhetrenyl-5-nitro-benzimidazole (Bzn-1) and 2-ferrocenyl-5-nitro-benzimidazole (Bzn-2) have been proposed as potential anti-Trypanosoma cruzi agents. On this regard, electrochemical, electron spin resonance and biological studies were carried out. Cyclic voltammetry experiments showed the generation of nitro anion radical derivatives and a self-protonation process was observed. Nitro anion radicals generated were characterized and analyzed using electron spin resonance spectroscopy. The compounds were tested in vitro against Trypanosoma cruzi (Dm28c strain). Biological evaluation display that 2-cyrhetrenyl-5-nitro-benzimidazole (Bzn-1) was more active than its ferrocene analogue (Bzn-2) and purely organic derivate (Bzn-3), associated with the electron-withdrawing properties of the (η5-C5H4)Re(CO)3 moiety. Finally, theoretical studies were carried out in order to elucidate the correlation between organometallic fragment, nitro-reduction potentials and trypanocidal activity.