M. Tyler Caudle

Manganese Redox Enzymes and Model Systems: Properties, Structures, and Reactivity

Publisher Summary This chapter discusses properties, structures, and reactivity of manganese redox enzymes and model systems. Manganese is one of several first-row transition elements that are employed by biological systems to assist in varied metabolic and structural roles. Manganese is used to give structural support to proteins and is a cofactor in chemical transformations that include hydrolytic and redox reactions. Perhaps the best-known function, and the one of great importance to aerobic life, is in the oxygen-evolving complex, which oxidizes water to dioxygen during photosynthesis. The discussions of data gathering on enzyme systems and model chemistry, both structural and functional, presented in this chapter provides a foundation for exploring current and as yet undiscovered manganese enzymes. The biological applications of manganese are numerous and quite varied. The manganese-containing redox enzymes are unique. Most of these deal with dioxygen metabolism in one form or another.

Isolation of the first ferromagnetically coupled Mn(III/IV) complex

Binuclear manganese complexes Mn2(III/IV)(dtsalpn)2DCBI, 1, Mn2(III/III)(dtsalpn)2HDCBI, 2, containing the ligand dicarboxyimidazole (DCBI) have been prepared in order to address the issue of imidazole bridged and ferromagnetically coupled Mn sites in high oxidation states of the OEC in Photosystem II (PS II). Temperature dependent magnetic susceptibility studies of 1 indicates that the interaction between the two Mn(III)/Mn(IV) ions is ferromagnetic (J = +1.4 cm(-1)). Variable temperature EPR spectra of 1 shows that a g = 2 multiline is as an excited state signal corresponding to S = 1/2.

μ-Oxido-bis[dichlorido(diethylamido-κN)(diethylamine-κN)titanium(IV)]

In the title compound, [Ti2(C4H10N)2Cl4O(C4H11N)2], the bridging O atom resides on an inversion center, resulting in a 180° Ti—O—Ti bond angle.