Elucidating Charge Carrier Reactivity, Conversion, and Degradation in n-Doped Oligo- and Poly(benzodifurandione)

n-Doped poly(benzodifurandione) (n-PBDF) has gained significant attention due to its solution processability and high electrical conductivity. However, the nature of charge carriers in n-PBDF remains poorly understood. In this study, we investigated a series of oligo(benzodifurandiones) (BFD1, BFD2, and BFD3), using previously reported BFD1 and BFD2 alongside newly synthesized BFD3, with a particular focus on the charged species of BFD3. Neutral BFD3 was successfully reduced to its hydride-adduct anion (BFD3H^–), radical anion (BFD3^•–), and dianion (BFD3^2–), the latter two behaving similarly to polarons and bipolarons respectively in n-PBDF. We conducted a characterization of their optical, electrochemical, and structural properties, and examined their interconversion and reactivity. Mass spectrometry analysis and absorption spectroscopy revealed that the BFD3^2– backbone undergoes degradation when further reduced, with proposed structural assignments for several degradation products. Notably, similar reactivity and degradation pathways were also identified in the polymeric system n-PBDF. These findings provide critical insights into the stability and reactivity of n-type charge carriers in π-conjugated polymers, establishing a foundation for future strategies to optimize doping levels and mitigate degradation in n-type organic electronic materials.