The Schiff bases are widely studied because of increasing recognition of their role in biological systems [1]. Their complexes are used in some chemical processes as catalysts such as C-C bond formation, redox reactions in manganese-enzyme and also as model to emulate activity of proteins [2]. The features of these compounds are also their preparative accessibility, diversity and structural variability, which make them very attractive [3]. Here we report series of manganese(II) complexes with Schiff bases were obtained by the condensation of o-phenylenediamine with 4-X-5-Y-2-hydroxybenzaldehyde (Y= H, NO2, Br; X= H, OMe ) and characterized by FT-IR, UV-Vis and Mass Spectroscopy. Also, their electrochemical properties were studied using cyclic voltammetry method. Trend of redox potentials of manganese(II) vary by para-substituent on the Schiff base ligands and are related with UV-Vis data as well as stretching frequency of C=N bands. Hammett equation was studied for the σ-para effect. These manganese(II) complexes with d5 electron configuration show less potentials changes than correspondence vanadyl Schiff base complexes with d1 electron configuration [4], upon substitution of X and Y on the ligand from Br group to electron withdrawing group NO2.
