Synthesis and characterisation of low valent Mn-complexes as models for Mn-catalases.

In this work we report the synthesis of two novel manganese complexes, L1(3)Mn(II)(6)(6) (1·(ClO(4))(6)) and L2Mn(II)(2)(μ-OAc)(μ-Cl)(2) (2·(ClO(4))(2)), where L1(2-) is the 2,2'-(1,3-phenylenebis(methylene))bis((2-(bis(pyridin-2-ylmethyl)amino)ethyl)azanediyl)diacetic acid anion and L2 is N1,N1'-(1,3-phenylenebis(methylene))bis(N2,N2'-bis(pyridin-2-ylmethyl)ethane-1,2-diamine). The ligands Na(2)L1 and L2 are built on the same backbone, L2 only contains nitrogen donors, while two carboxylate arms have been introduced in Na(2)L1. The two complexes have been characterized by single-crystal X-ray diffraction, magnetic susceptibility, EPR spectroscopy, and electrochemistry. X-Ray crystallography revealed that 1 is a manganese(II) hexamer and 2 is a manganese(II) dimer featuring an unprecedented mono-μ-acetato, mono-μ-chlorido bridging motif. The ability of the complexes to catalyse H(2)O(2) disproportionation, thereby acting as models for manganese catalases, has been investigated and compared to the activity of two other related manganese complexes. The introduction of carboxylate donors in the ligands, leading to increased denticity, resulted in a drop in H(2)O(2) disproportionation activity.