Two new iron complexes, [(L5FeCl)-Fe-3-Cl-II]PF6 (1.PF6) and [((L5H+)-H-3)(FeCl3)-Cl-III]PF6 (2.PF6), were synthesized (L-5(3) = N-methyl-N, N', N'-tris(2-pyridylmethyl) propane-1, 3-diamine), and their molecular structures were determined by X-ray crystallography. Their behavior in solution was studied by UV-vis spectroscopy and electrochemistry. Upon addition of a base to an acetonitrile solution of 2, the new unsymmetrical dinuclear complex [(L5FeOOFeCl3)-Fe-3-O-III-Cl-III](+) was detected. Treating 1 with hydrogen peroxide has allowed us to detect the low spin [(L5FeOOH)-Fe-3-O-III](2+). Its spectroscopic properties (UV-vis, EPR and resonance Raman) are similar to those reported for related FeOOH complexes obtained with amine/pyridine ligands. Using stopped-flow absorption spectroscopy, the formation and degradation of [(L5FeIII)-Fe-3-OOH](2+) has been monitored, and a mechanism is proposed to reproduce the kinetic data.