Manganese oxides with tunnel structures

The fundamental structural unit in Mn(IV) oxides is the [Mn06] octahedron, in which Mn4 ions with their 3d3 electronic configuration acquire exceptionally high CFSE, perhaps exceeding 300 kJ/g ion (cf table 2.5). The [Mn06] 

Lattice imaging by high resolution transmission electron microscopy (HRTEM) of fibrous manganese(IV) oxide minerals demonstrated the exis- 

The cation occupancies of todorokite may also account for the relative stability of this mineral towards oxidation. Todorokite is destabilized by the presence of substantial Mn2+ and Mn3+ ions in the structures, because these cations are vulnerable to oxidation. Thus, Mn2+-bearing todorokites show oxidation to manganite and vemadite. However, replacement of Mn2+ or Mn3+ by Mg2+, Ni2+, Zn2+ and Cu2+, which are not susceptible to oxidation, stabilizes todorokite, particularly in manganese nodule deposits. 

---

Table 1. Crystallographic data for manganese oxides with tunnel structures... 

An efficient oxidation catalyst, OMS-1 (octahedral mol. sieve), was prepared by microwave heating of a family of layered and tunnel-structured manganese oxide materials. These materials are known to interact strongly with microwave radiation, and thus pronounced effects on the microstructure were expected. Their catalytic activity was tested in the oxidative dehydrogenation of ethylbenzene to styrene [25]. 

---