Reflectance spectra of bis-fused TTF radical-cation salts

Polarized reflectance spectra were measured on bis-fused TTF radical-cation salts. The conductivity spectra of (TTM-TTP)I3 exhibit an optical gap around 1000 cm−1 at room temperature, despite the metallic behavior in DC conductivity down to 160 K. The effective onsite Coulomb repulsion in the Hubbard model, U, is evaluated to be 0.5 eV, by use of the one-dimensional regular-stack model. The reflectance spectra of (TMET-TTP)(PF6)0.27 exhibit two-dimensional weak dispersions in the infrared region, being consistent with semiconductive behavior of this salt.