Comparative optical investigations on the one-dimensional organic metals (perylene)2(PF6)1.1x0.8CH2Cl2, (pyrene)12(SbF6)7 and fluoranthene)2(AsF6)0.2(PF6)0.8

Abstract

The reflectance spectra of different radical cation salts of the type (arene)2XF6 are reported (X=P, As, Sb). For light polarised perpendicular to the molecular stacks, the crystals exhibit the optical behaviour of an insulating molecular crystal, whereas for light polarised parallel to the stacks a pronounced plasma edge is observed. Compared to other organic metals the crystals show remarkably high values of the plasma energy. Because the concentration of the free carriers is obtained from the charge transfer between the radical cations and the inorganic counter ions, the effective mass of the free carriers may be calculated from the plasma frequency. The analysis of the reflectance data by a Lorentz-Drude model yields as well the values of the mean collition time, the electrical conductivity, and the bandwith.