Synthesis, characterization and X-ray crystal structure of potentially N6O2 coordinating macroacyclic Schiff base ligands and their Mn(II), Zn(II) and Cd(II) complexes; cytotoxic, antibacterial properties and competitive 7Li NMR studies

In this work, two new symmetrical, potentially N6O2 coordinating, macroacyclic Schiff base ligands (H2L1 and H2L2) were derived from the condensation of a newly synthesized polyamine, 2,2′-(ethane-1,2-diylbis(piperazine-4,1-diyl))bis(ethan-1-amine) (A), with 2-hydroxybenzaldehyde and 2-hydroxy-3-methoxybenzaldhyde respectively. Six macroacylic Schiff base complexes were prepared by direct reaction of H2L1 or H2L2 with Mn(II), Zn(II) or Cd(II) metal ions in equimolar ratios. The products were characterized by several physicochemical measurements. As well, the crystal structure of H2L1 was confirmed by a single crystal X-ray structural analysis. Competitive 7Li NMR experiments were used to probe the complexation of Mn2+, Zn2+ and Cd2+ ions with (H2L1) and (H2L2) in both acetonitrile and methanol. The stabilities of the final complexes were found to be in the order M–(H2L1) > M–(H2L2) and Cd2+ > Zn2+ > Mn2+. The cytotoxic and antibacterial properties of these complexes were also investigated.