Manganese catalase mimics

In 1992, Wieghardt and co-workers reported two manganese catalase mimics based on triazacyclononane ligands 294). These were asymmetric complexes, with one half bearing an A(,A(, iV -trimethyl-... 

Figure 11.1 Ligand sets developed for manganese complexes as catalase mimics.

Sakiyama explored various dinuclear manganese complexes as catalase mimics derived from 2,6-bis N-[(2-dimethylamino)ethyl]iminomethyl-4-methylphenolate (2, Figure 10.1) and related ligands. Employing UV- ds and MS techniques both mono-and di-Mn -oxo intermediates could be detected [30]. Notably, the proposed mechanism (Scheme 10.2) is different from that reported for the manganese catalases and model compounds containing ligand 1 [30]. 

Manganese is used by nature to catalyze a number of important biological reactions that include the dismutation of superoxide radicals, the decomposition of hydrogen peroxide, and the oxidation of water to dioxygen. The dinuclear manganese centers that occur in Lactobacillus plantar-aum catalase and Thermus thermophilus catalase have attracted considerable attention and many model compounds have now been synthesized that attempt to mimic aspects of these biological systems.The catalases have at least four accessible oxidation states (Mn Mn , Mn°Mn , Mn" Mn", and Mn Mn ) it is believed that the Mn"Mn"/Mn"Mn" redox couple is effective in catalyzing the disproportionation of water. 

One of the earliest functional mimics of catalase was reported by Mathur et al. in 1987 (438). This system employed the ligand N, N, N, N -tetrakis-(a- methylenebenzimidazolato)- 1,3-diaminopro-pane-2-ol. The complex formed with this ligand is composed of one ligand, with the alkoxide bridging the two manganese(II) ions, with a proposed bridging chloride and two terminal chlorides, one on each... 

---