Mono-, di- and tri-nuclear manganese(II) complexes derived from a quinquedentate ligand: Superoxide dismutase and catalase mimetic studies

• A pentadentate Schiff base ligand and its mono and trinuclear Mn(II) complexes were synthesized.
• Mn2Ca complex of the ligand was also synthesised.
• Solid state structures of the complexes were determined by single crystal X-ray diffraction study.
• Superoxide dismutase and catalase activities of the complexes were evaluated.

In this study, three manganese complexes [Mn(H2L)Cl2]·MeOH, [Mn3(L)2(OAc)2(MeOH)2]·2MeOH and [Mn2Ca(L)2(OAc)2(MeOH)2]·2MeOH derived from a quinquedentate Schiff base ligand (H2L) were synthesised and characterised by the spectroscopic and analytic methods. Molecular structures of the complexes were determined by single crystal X-ray diffraction studies. In mononuclear complex [Mn(H2L)Cl2]·MeOH, the Mn(II) ions are seven-coordinate pentagonal bipyramidal geometry with two chloride ions at the axial positions. The trinuclear complex [Mn3(L)2(OAc)2(MeOH)2]·2MeOH consists of two mononuclear units linked by a central Mn(II) ion. The calcium containing complex [Mn2Ca(L)2(OAc)2(MeOH)2]·2MeOH contains two mononuclear units bridged by a six-coordinate Ca(II) ion. The superoxide dismutase (SOD activities of the structurally complexes were evaluated and the mononuclear complex [Mn(H2L)Cl2]·MeOH showed the greatest SOD activity with an IC50 value of 0.95 μM which gives a calculated kcat value of 1.67 × 106 M−1 s−1. Finally, the ability of the complexes to disproportionate H2O2 in the presence of base was tested by measuring the rate of oxygen evolution at room temperature. The trinuclear [Mn3(L)2(OAc)2(MeOH)2]·2MeOH complex is the most efficient complex catalase mimic of the tested complexes with the fastest rate 5.33 ml/s.

In this study, a Schiff base ligand and its mono, di- and trinuclear Mn(II) complexes were prepared and characterised by spectroscopic and analytical methods. Molecular structures of the complexes were determined by single crystal X-ray diffraction study. Additionally, SOD and catalase activities for the complexes were investigated.Figure optionsDownload as PowerPoint slide