PEIERLS TRANSITION OF PERYLENE RADICAL-CATION SALTS WITH 5 8-FILLED CONDUCTION-BAND/

The Peierls transition of Perylene (PE) radical cation salts (PE)(2)X( 1) . 2/3THF (nominal composition, X = (PF6)(1-x)(AsF6)(x), 0 less than or equal to x less than or equal to 1, THF = tetrahydrofuran) was ana lysed by static magnetic susceptibility (chi), radiofrequency and micr owave electron spin resonance (ESR), (g-factor, line width Delta B), a nd microwave conductivity (sigma). According to crystal structure anal yses, these salts have a five-eighth filled conduction band. The openi ng of the energy gap at 100 - 120 K (depending on x) was determined by the analysis of (chi)(T) Additional phase transitions were observed a nd analysed by the different experimental techniques ((chi)(T), sigma( T), g(T)). Due to the narrow ESR line in the metallic phase (Delta Bpp similar or equal to 15 mG), a reorientation of the PE-stacks at 162 K can be derived precisely via the g-anisotropy. In the low-temperature phase the angular and frequency dependence of the ESR lines' broadeni ng is used in order to analyse the interaction between thermally activ ated conduction electrons and localized defects in these quasi-onedime nsional conductors.