A copper(II) complex with o ‐phthalate acid [Cu( o ‐phth)(H 2 O)] n (1) and a cobalt(II) complex with 3‐nitro‐phthalic acid and 4,4′‐bipyridine [Co(3‐nitro‐phth) (4,4′‐bipy) 2 (H 2 O) 3 ] n (2) have been synthesized. These two novel complexes were characterized by IR, X‐ray crystallography diffraction. Complex 1 belongs to monoclinic crystal with C2 (1)/c space group, the complex 2 triclinic crystal with P‐1. Also, electrochemical properties of these complexes and thermal decomposition process of complex 1 were investigated. [ABSTRACT FROM AUTHOR]