1.2- Dithiolenes spin-Peierls systems

This section is devoted to four main topics spin-Peierls systems, spin-ladder systems, systems exhibiting ferromagnetic interaction, and bulk ferromagnets. To our knowledge, no dithiolene-based films (including LB films) have been studied for their ferromagnetic properties and no patent has claimed the use of these materials in this area. 

The spin-Peierls transition (18, 19) is a peculiar magnetoelastic transition that may take place in a limited series of quasi ID insulating systems (20, 286). It is interesting to note that, for once, this behavior had been theoretically predicted for organic free radicals (18, 19) long before its experimental observation. It happened that the first experimental observation of a spin-Peierls system was reported for dithiolene systems, namely, (TTF)[M(tfd)2], where M is Cu or Au (25, 26). However, since bis(l,2-dithiolene) complex-based compounds have a tendency to form ID stacks (see above), this priority is not truely amazing. 

A large number of papers have appeared on this research reporting additional theoretical and experimental studies on the (TTF)[M(tdf)2] (M = Cu, Au) compounds, and detailed reviews are available (20, 286). Note, however, that these dithiolene complex-based compounds were the first members of the quite limited series of spin-Peierls systems. Among these, another related, selenium analogue dithiolene complex-based compound, (TTF) Cu[Se2C2(CF3)2]2, also undergoes a spin-Peierls transition at 6 K (290). 

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