Jago David, Liu Chongguang, Daaoub Abdalghani H S, Gaschk Emma, Walkey Mark C, Pulbrook Thea, Qiao Xiaohang, Sobolev Alexandre N, Moggach Stephen A, Costa-Milan David, Higgins Simon J, Piggott Matthew J, Sadeghi Hatef, Nichols Richard J, Sangtarash Sara, Vezzoli Andrea, Koutsantonis George A
School of Molecular Science, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia, 6009, Australia.
Department of Chemistry, University of Liverpool, Crown St, Liverpool, L69 7ZD, UK.
Small. 2024 Feb;20(8):e2306334. doi: 10.1002/smll.202306334. Epub 2023 Oct 10.
While a multitude of studies have appeared touting the use of molecules as electronic components, the design of molecular switches is crucial for the next steps in molecular electronics. In this work, single-molecule devices incorporating spiropyrans, made using break junction techniques, are described. Linear spiropyrans with electrode-contacting groups linked by alkynyl spacers to both the indoline and chromenone moieties have previously provided very low conductance values, and removing the alkynyl spacer has resulted in a total loss of conductance. An orthogonal T-shaped approach to single-molecule junctions incorporating spiropyran moieties in which the conducting pathway lies orthogonal to the molecule backbone is described and characterized. This approach has provided singlemolecule conductance features with good correlation to molecular length. Additional higher conducting states are accessible using switching induced by UV light or protonation. Theoretical modeling demonstrates that upon (photo)chemical isomerization to the merocyanine, two cooperating phenomena increase conductance: release of steric hindrance allows the conductance pathway to become more planar (raising the mid-bandgap transmission) and a bound state introduces sharp interference near the Fermi level of the electrodes similarly responding to the change in state. This design step paves the way for future use of spiropyrans in single-molecule devices and electrosteric switches.
尽管已有大量研究吹捧将分子用作电子元件，但分子开关的设计对于分子电子学的后续发展至关重要。在这项工作中，描述了使用断接技术制备的包含螺吡喃的单分子器件。此前，带有通过炔基间隔基连接到二氢吲哚和色酮部分的电极接触基团的线性螺吡喃提供了非常低的电导值，而去除炔基间隔基导致电导完全丧失。本文描述并表征了一种正交T形方法，用于制备在其中导电通路与分子主链正交的包含螺吡喃部分的单分子结。这种方法提供了与分子长度具有良好相关性的单分子电导特征。利用紫外光或质子化诱导的开关作用，可以获得额外的高导电状态。理论建模表明，在（光）化学异构化为部花青时，两种协同现象会增加电导：空间位阻的释放使电导通路变得更加平面化（提高带隙中间的传输），并且一个束缚态在电极的费米能级附近引入尖锐的干涉，同样对状态变化做出响应。这一设计步骤为螺吡喃在单分子器件和电空间开关中的未来应用铺平了道路。
