Annelated vs. non-annelated hopping sites in periodically twisted molecular wires

Abstract To realize efficient intramolecular hopping transport, molecular wires must possess both a small reorganization energy (λ) at the hopping site and a minimal energy difference (ΔEhs) between them. While we showed that periodically twisted molecular wires using an annelated unit (TBID) as a hopping site improves hopping transport, the influence of the chemical structure of the hopping site remains unclear. Here, to investigate the impact of the annelated structure on hopping transport, we designed a non-annelated unit (BPB) and developed molecular wires based on periodically twisted BPB. Physical properties of BPB were compared with those of TBID. Molecular wires based on BPB showed lower single-molecule conductance than those based on TBID. Theoretical calculations indicate that BPB has a larger λ, ΔEhs, as well as a higher injection barrier compared to TBID. These results demonstrate the importance of the annelated structure at the hopping site for achieving efficient hopping transport.