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

Two new potentially tetradentate Schiff base ligands N'-(pyridin-2-ylmethylene)nicotinohydrazide ( L 1 ), and N'-(pyridin-2-ylmethylene)isonicotinohydrazide ( L 2 ) were synthesized. Reactions of hydrazone ligands L 1 and L 2  with Mn(NO 3 ) 2 afford two mononuclear Mn(II) complexes, [Mn( L 1 )(NO 3 )(H 2 O) 2 ]•(NO 3 ) ( 1 ) and [Mn( L 2 ) 2 (NO 3 )(H 2 O)]•(NO 3 ) ( 2 ). For complexes 1 and 2 , L 1 and L 2 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.