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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 (E_CA) is poised below the oxidation potential of the COEs (E_CA= 200 mV) in three‐electrode electrochemical cells containingShewanella oneidensisMR‐1, addition of DVFBO and F₄‐DVFBO produces negligible biocurrent enhancement over controls. AtE_CA= 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.

Polymorphism, the ability for a given material to adopt multiple crystalline packing states, is a powerful approach for investigating how changes in molecular packing influence charge transport within organic semiconductors. In this study, a new “thin film” polymorph of the high‐performance, p‐type small molecule N‐octyldiisopropylsilyl acetylene bistetracene (BT) is isolated and characterized. Structural changes in the BT films are monitored using static and in situ grazing‐incidence X‐ray diffraction. The diffraction data, combined with simulation and crystallographic refinement calculations, show the molecular packing of the “thin film” polymorph transforms from a slipped 1D π‐stacking motif to a highly oriented and crystalline film upon solvent vapor annealing with a 2D brick‐layer π‐stacking arrangement, similar to the so‐called “bulk” structure observed in single crystals. Charge transport is characterized as a function of vapor annealing, grain orientation, and temperature. Demonstrating that mobility increases by three orders of magnitude upon solvent vapor annealing and displays a differing temperature‐dependent mobility behavior.