Electronic Structures of 2,7-Bis(methylthio)-1,6-dithiapyrene (MTDTPY) Charge Transfer Complexes

Polarized reflection spectra were measured on two charge-transfer complexes of 2,7-bis(methylthio)-1,6-dithiapyrene (MTDTPY) with chloranil and 7,7,8,8-tetracyanoquinodimethane (TCNQ), which showed metallic conductivity. In spite of short intercolumnar S–S contacts, the spectra showed a strong one-dimensional character. The optical conductivity spectra, σ(ω), and real part of the dielectric constant, e′(ω), along the stack axis were obtained by means of Kramers–Kronig transformation. The conductivity spectra and the dielectric constant of both complexes substantially differ from the simple Drude model. These results were analyzed with a one-dimensional electron localization model in a disordered system with the optical parameters: ωp=13500 cm−1, τi=1.6×10−15s (τi−1=3300 cm−1) for chloranil complex and ωp=12000 cm−1, τi=2.5×10−15s (τi−1=2100 cm−1) for TCNQ complex.