Abstract EN:

This thesis reports the synthesis of two heterocyclic aromatic cations formally derived from the fluoranthene, as precursors of new organic materials with very narrow ESR lines. Their uses as magnetic field probes, although possible, were limitated so far by the poor stability of the known materials, e. G. Cation radical salts of naphtalene and fluoranthene. The major objective of this work was to introduce heteroatoms in the carbon frame in order to improve their stability. We then target the two following molecules: 3a-azonia fluoranthene (3a-AF) and 3b-azonia fluoranthene (3b-AF). Short, efficient syntheses of these two new heterocyclic cations are presented which avoid any potentially troublesome reduction or dehydrogenation step. A comparaison of the physical and chemical characteristics of the two salts with the parent arene shows that the 3b-AF indeed behaves like a charged fluoranthene while the 3a-AF is more reminiscent of a quinolizinium. The chemically generated 3b-AF neutral radical is characterized by EPR. Cyclic voltammetry experiments indicate that the 3b-AF reduces to the neutral radical at -0. 9V/SCE; this prevents its use in standard conditions. Finally single crystals of a 1:2 TCNQ salt of 3b-AF have been prepared electrochemically. Their semi-conducting behaviour is compared with that of other TCNQ salts.