Electronic properties of p-type doped copolymers consisting of oligothienylene and disilanylene units

In association with the previous theoretical prediction on the ferromagnetic spin correlation in p-type doped poly[disilanylene(thienylene)(n)] (PDST-n, n = 1-5), we have actually prepared these samples and examined their electronic properties by the combination of cyclic voltammetry (CV), ultraviolet-visible-near-infrared (UV-vis-NIR), electron spin resonance (ESR), and infrared (IR) spectroscopic measurements. It has been confirmed that electrons are removed mainly from oligothienylene units. A spin generated by the doping was found to be localized at 3p(pi)-atomic orbitals (AOs) of sulfur atom at n = 1. For n = 2-5 a spin was the polaronic pi-spin delocalized within an oligothienylene unit. These natures of radical spins are in accordance with the previous theoretical study. However, the spin concentration of p-type doped polymers was considerably small (1 spin/ca. 400 oligothienylene units), possibly due to the aggregation of the oligothienylene units around the dopant and to the degradation of disilanylene units. No signs of ferromagnetic interaction has been observed yet due to such small spin concentrations.