Binuclear Species in 2H Perovskite Derived Systems

Some of the binuclear systems reported so far derive from the 2H hexagonal-like structure described above, in which only two-thirds of the octahedral sites are occupied by metal ions. 

The ordering between occupied and empty sites results in isolated binuclear units aligned along the c axis each one may be schematized as two octahedra sharing a face, so that the site symmetry is C3v and the molecular symmetry 

D3h (Fig. 9). Thus, Cs3Fe2F9, Cs3M2C19 (with M=Ti,V), Cs3Gd2Br9 and Cs3V202F7 where shown to present the same structural features [44, 48]. 

Owing to the metal-metal distances between adjacent dimers ( 4.8 A), they are expected to behave as isolated binuclear species whose behavior may accurately be discussed from rigorous quantum analysis. 

The simplest case corresponds to Cs3Fe2F9 the behavior of which is plotted in Fig. 10, in the temperature range 2-40 K [49]. The increase of X T, upon 

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