Tuning the Potential of Electron Extraction from Microbes with Ferrocene‐Containing Conjugated Oligoelectrolytes

Abstract Synthetic systems that facilitate electron transport across cellular membranes are of interest in bio‐electrochemical technologies such as bio‐electrosynthesis, waste water remediation, and microbial fuel cells. The design of second generation redox‐active conjugated oligoelectrolytes (COEs) bearing terminal cationic groups and a π‐delocalized core capped by two ferrocene units is reported. The two COEs, DVFBO and F4‐DVFBO, have similar membrane affinity, but fluorination of the core results in a higher oxidation potential (422 ± 5 mV compared to 365 ± 4 mV vs Ag/AgCl for the neutral precursors in chloroform). Concentration‐dependent aggregation is suggested by zeta potential measurements and confirmed by cryogenic transmission electron microscopy. When the working electrode potential (ECA) is poised below the oxidation potential of the COEs (ECA = 200 mV) in three‐electrode electrochemical cells containing Shewanella oneidensis MR‐1, addition of DVFBO and F4‐DVFBO produces negligible biocurrent enhancement over controls. At ECA = 365 mV, DVFBO increases steady‐state biocurrent by 67 ± 12% relative to controls, while the increase with F4‐DVFBO is 30 ± 5%. Cyclic voltammetry supports that DVFBO increases catalytic biocurrent and that F4‐DVFBO has less impact, consistent with their oxidation potentials. Overall, electron transfer from microbial species is modulated via tailoring of the COE redox properties.