Synthesis, Structural Diversity and Mimic Superoxide Dismutase of Mn(II) Complexes Derived from N, O-donor Schiff-bases

Abstract

Two new potentially tetradentate Schiff base ligands N'-(pyridin-2-ylmethylene)nicotinohydrazide (L₁), and N'-(pyridin-2-ylmethylene)isonicotinohydrazide (L₂) were synthesized. Reactions of hydrazone ligands L₁ and L₂ with Mn(NO₃)₂ afford two mononuclear Mn(II) complexes, [Mn(L₁)(NO₃)(H₂O)₂]•(NO₃) (1) and [Mn(L₂)₂(NO₃)(H₂O)]•(NO₃) (2). For complexes 1 and 2, L₁ and L₂ act as pincer-like tridentate or bidentate ligands, respectively. The Mn(II) ions in the two compounds are both in heptacoordinated environment, while the two molecules display diverse solid-state supramolecular structures because of the different orientation of N_pyridine and hydrogen bonding patterns of nitrate anions. Complex 1 features 2D supramolecular sheet, while complex 2 is double-chain supramolecular structure. Both of the two complexes exhibit moderate superoxide dismutase (SOD) mimetic activity.