Two iron(II) complexes of the pentadentate aminopyridine ligand L52(OH), bearing a 2nd sphere OH group in ortho position of one pyridine, were studied in the oxidation of various substrates using H2O2. While the addition of the OH group lowers the yields of alkane and aromatic oxidation, it improves the yield in alkene epoxidation. Spectroscopic analyses suggest that the pyridine-OH group stabilizes an Fe(III)OOH intermediate by hydrogen-bonding with the proximal O atom of hydroperoxo, but also eventually drives the system towards a dimeric structure, which competes with the oxidation process. The improvement in epoxidation yields is proposed to result from the fast reaction of cyclooctene with the active species, together with an enhanced oxidizing power induced by the hydrogen-bonding pattern.