Competing Charge Transport Pathways
A Spirobifluorene-Based Molecular Loop
Brian Ogi (University of Basel)
R. Conte (TU Delft - Applied Sciences, Kavli institute of nanoscience Delft)
Salome L. Heim (University of Basel)
H.S.J. van der Zant (TU Delft - Applied Sciences)
Marcel Mayor (University of Basel, Sun Yat-sen University, Karlsruhe Institut für Technologie)
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Abstract
Understanding the relationship between molecular structure and charge transport remains a crucial aspect towards integrating single molecules into electronic devices, especially in systems which feature multiple conducting pathways. Here we report the synthesis of a molecular loop that incorporates a rigid 9,9′-spirobifluorene (SBF) core as a central mounting point for thiol anchoring groups and a cycloparaphenylene (CPP) backbone. The model compound is synthesized by a Suzuki–Miyaura coupling between a CPP precursor and a functionalized SBF derivative, followed by reductive aromatization of the macrocycle. The resulting macrocycles are fully characterized and enantiomerically resolved by chiral high-performance liquid chromatography (HPLC), and their chiroptical properties are investigated. Conductance measurements in a mechanically controlled break-junction (MCBJ) setup demonstrate reproducible single-molecule junction formation with two dominant conductance plateaus near 2 × 10−4 G0 and 4 × 10−5 G0, observed across different samples and applied voltages. The observed conductance features are consistent with multiple reproducible junction configurations, highlighting the molecular loop as a promising platform for studying charge transport through multiple intramolecular pathways.
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