Optical study on bis(propylenedithio)tetrathiafulvalenium (BPDT-TTF) salts

Abstract

Polarized reflectance spectra of (BPDT-TTF) 3(PF 6) 2 and (BPDT-TTF) 2I 3 were measured at room temperature over the spectral region from 720 cm −1 to 25 000 cm −1. Both of these salts exhibited one-dimensional behaviour in contrast to the BEDT-TTF (bis-(ethylenedithio)tetrathiafulvalenium) salts. The transfer integrals and the on-site Coulomb energy of these materials were estimated by analysing the optical spectra, and the on-site Coulomb energy of (BPDT-TTF) 3(PF 6) 2 was found to be significantly larger than that of TCNQ salts.