Abstract EN:

Radical-cation salts derived from polyaromatic donors exhibit very interesting EPR properties. Thus, the linewidth of the material (fluo­19 ranthene) 2PF6 is only 10 mG. However, the high thermal instability of these solids has so far precluded industrial applications. Our goal was to obtain stable materials with a narrow EPR line. We assumed that the high oxydation potentials of the substrates was one of the reasons of the instability. We have tried to lower these potentials by an adequate substitution of the aromatic molecules, the effect of this substitution being also to modify dimensionnality of the materials, a factor which would predictibly affect the linewidth. We have prepared two substituted perylenes, using an original synthesis. One of the them, the 3,4,9,10-tetramethylperylene, led to a radicalcation salt, with a 2:1 stoechiometry. The linewidth of this material is 16 mG, its thermal stability is very good up to 80°C. We then attempted to investigate the factors which might be responsible of the narrowing of the line, in this series deriving from perylene. Therefore, we prepared and studied the 2:1 radical-cation salts of perylene itself. We prepared also the 2:1 salt deriving from 1,2,7,8 -tetrahydro­ [cd;1m]dicyclopentaperylene, which had already been described. The comparison of the structural data allowed us to show unambiguously the beneficial effect of the dimensionnality on the linewidth. It seems possible, adopting the same approach we used for perylene, to obtain materials with still narrower EPR lines by adequatly substituting the suitable substraces. The communication of the contents of this thesis is submitted to the authorization of the Thomson-Sintra ASM company.