Manganese Jahn-Teller effect

Spin-crossover phase transition of a manganese(IU) complex [Mn(taa)] was studied by variable-temperature laser Raman spectroscopy and it was found that the vibrational contribution in the transition entropy is not dominant in contrast to the cases of ordinary iron spin-crossover systems. The discovery of a dynamic disorder in the HS phase by means of dielectric measurements provided an alternative entropy source to explain the thermally induced spin-crossover transition. This dynamic disorder was attributed to the reorienting distortion dipoles accompanying the E e Jahn-Teller effect in HS manganese(III) ions. 

In alkali amphiboles, in which sodium fills the M4 positions, trivalent cations (Fe3+, Al3+) are largely confined to the smaller distorted octahedral M2 sites, so that the ordering pattern for Fe2+ ions becomes M3 > Ml M2. In the manganese-bearing alkali amphiboles winchite and juddite, Mn3+ ions are ordered in the M2 sites (Ghose et al., 1986), in which they are stabilized by the Jahn-Teller effect ( 6.3). 

There are three kinds of Mn-0 distances within each oxygen octahedron surrounding a central manganese ion two of them are shorter (0.191 and 0.195 nm for PrMnOj, and 0.194 and 0.190 for TbMnOj) and the other is a little longer (0.222 nm for PrMnOj and 0.223 nm for TbMnOj). Thus each oxygen octahedron distorts and tilts each other, which are caused by the Jahn-Teller effect of trivalent manganese ion. Each rare... 

The literature is replete with examples of crystallographic studies of copper(II) and manganese(III) complexes where the MLe skeletal framework is reported to be regular. In these instances it is not uncommon to read of the Jahn-Teller effect being suppressed . The use of such language could be taken to mean that the potential... 

A4 DYNAMICAL JAHN-TELLER EFFECTS IN SYSTEM - AQUEOUS MANGANESE(III) AND OTHER COMPLEXES OF Mn(III) AND Cr(III),... 

Bhattacharyya, B.D. Phys. Status Solidi B43 (1971)495. Jahn-Teller effect in the ligand field theory of tris(acetylacetonato)manganese(III). 

Schematic illustration of Jahn-Teller effects in manganese oxides (a) Mn h 3d with cubic symmetry (no Jahn-Teller effect), (b) Mn +r 3d with tetragonal symmetry (Jahn-Teller effect). (From Manthiram, A. and Kim, J., Recent Res. Dev. Electrochem., 2,1999.)...

The ionic radii of manganese(II) and manganese(III) are taken from Shannon (1976) as 0.83 and 0.645 A, respectively. Both are for a six-coordinate ion with high spin. However, the Jahn-Teller effect is hkely to lead to stronger bonds in manganese(III), as also occurs with copper(II), with an apparent reduction in ionic radius (see Chapter 16). 

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