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<p>Helicenes, composed of <i>ortho</i>-fused benzene rings, possess a spring-like π-backbone, enabling electron delocalization through both bonds and space. Theoretical predictions suggest that mechanical stretching or compression of molecular junctions in higher-order diazahelicenes could increase conductance and thermopower. However, this theory has not been experimentally verified, likely due to the difficulty of forming robust higher-order helicene molecular junctions using existing heteroatom anchors and the high electrical resistance of metal–heteroatom bonds. Thus, constructing mechanically stable single-molecule junctions through multipoint metal–π interactions would be ideal. Here we verify this theory using a 3D carbohelicene with a shielded π-face bearing bulky <i>tert</i>-butyl groups and an exposed π-face lacking <i>tert</i>-butyl groups. This partially π-exposed 3D carbohelicene forms a robust monolayer on the Au(111) substrate at room temperature through multipoint metal–π interactions. Using the break-junction technique, we demonstrate a compression-induced increase in both peak conductance (10<sup>–3</sup>–10<sup>–2</sup> G<sub>0</sub>) and thermopower (−44 μV/K).</p>

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Partially π-exposed 3D carbohelicene for mechanical tuning of conductance and thermopower in single-molecule junctions

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年4月27日

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  • Shintaro Fujii,
  • Futo Morita,
  • Kanato Takahashi,
  • Juntaro Nogami,
  • Yuko Kishida,
  • Haruki Goto,
  • Ryota Shimizu,
  • Tomoaki Nishino,
  • Hidehiro Uekusa,
  • Ken Tanaka

摘要

Helicenes, composed of ortho-fused benzene rings, possess a spring-like π-backbone, enabling electron delocalization through both bonds and space. Theoretical predictions suggest that mechanical stretching or compression of molecular junctions in higher-order diazahelicenes could increase conductance and thermopower. However, this theory has not been experimentally verified, likely due to the difficulty of forming robust higher-order helicene molecular junctions using existing heteroatom anchors and the high electrical resistance of metal–heteroatom bonds. Thus, constructing mechanically stable single-molecule junctions through multipoint metal–π interactions would be ideal. Here we verify this theory using a 3D carbohelicene with a shielded π-face bearing bulky tert-butyl groups and an exposed π-face lacking tert-butyl groups. This partially π-exposed 3D carbohelicene forms a robust monolayer on the Au(111) substrate at room temperature through multipoint metal–π interactions. Using the break-junction technique, we demonstrate a compression-induced increase in both peak conductance (10–3–10–2 G0) and thermopower (−44 μV/K).