Shi Wanzhuo, Wang Mengjiao, Venkataraman Latha, Tovar John D
Department of Chemistry, Columbia University, New York, New York 10027, United States.
Institute of Science and Technology Austria, 3400 Klosterneuberg, Austria.
Nano Lett. 2025 Aug 6;25(31):12101-12106. doi: 10.1021/acs.nanolett.5c03693. Epub 2025 Jul 24.
We describe the design, synthesis, and single-molecule junction conductance of π-electron molecules bearing both radial and linear π-conjugation pathways, whereby cycloparaphenylene (CPP) radial cores are π-extended linearly with aryl alkyne substituents as models for previously reported CPP-arylene ethynylene conjugated polymers. Although radially and linearly conjugated molecules have been studied previously in isolation as junction-bridging molecular electronic units, this is the first study to examine molecules where both topologies are operative. Our results reveal that the presence of radial CPP components within the junction-spanning pathway leads to a reduction in the conductance of the backbone compared to model linear phenyl substituents. Through tight-binding and DFT-based calculations, we attribute this conductance change to intramolecular van der Waals (vdW) interactions between the CPP ring and the junction-spanning arylene-ethynylene molecular backbone. These interactions induce changes in the dihedral angles of the backbone, leading to a reduced overlap of π orbitals within the molecular junction.
我们描述了具有径向和线性π共轭途径的π电子分子的设计、合成及单分子结电导，其中环对亚苯基（CPP）径向核心通过芳基炔取代基进行线性π扩展，以此作为先前报道的CPP - 亚芳基乙炔共轭聚合物的模型。尽管先前已分别研究了作为结桥连分子电子单元的径向和线性共轭分子，但这是首次对两种拓扑结构均起作用的分子进行研究。我们的结果表明，与模型线性苯基取代基相比，跨越结的途径中径向CPP组分的存在导致主链电导降低。通过基于紧束缚和密度泛函理论（DFT）的计算，我们将这种电导变化归因于CPP环与跨越结的亚芳基乙炔分子主链之间的分子内范德华（vdW）相互作用。这些相互作用引起主链二面角的变化，导致分子结内π轨道的重叠减少。
