瑞士苏黎世IBM欧洲研究院Gross, Leo团队报道了茚二[1,2-a]芴中π-双自由基开壳和闭壳态的双稳定性。相关研究成果于2024年2月8日发表于国际一流学术期刊《自然—化学》。

独立芴是一种非苯类共轭烃，由于其不同寻常的电子结构和在非线性光学和光伏中的潜在应用而引起人们的极大兴趣。

该文中，研究人员报道了通过扫描隧道显微镜和原子力显微镜的尖端施加的电压脉冲，通过裂解7，12-二氢茚并[1，2-a]芴中的两个C–H键，在不同表面上生成未取代的茚并[1,2-a]芴。在Au（111）上的双层NaCl上，茚并[1，2-a]芴处于中性电荷状态，但在Ag（111）和Cu（111）的双层NaCl的低功函数表面上，它表现出中性和阴离子状态之间的电荷双稳态。

在中性态下，茚并[1，2-a]芴表现出两种基态之一：开壳层π-二自由态，通过密度泛函和多参考多体微扰理论计算预测为三重态，或在茚并苯核中具有对醌二甲烷部分的闭壳层。通过改变单个分子在NaCl上的吸附位点，观察到单个分子在开壳层和闭壳层状态之间的切换。

附：英文原文

Title: Bistability between π-diradical open-shell and closed-shell states in indeno[1,2-a]fluorene

Author: Mishra, Shantanu, Vilas-Varela, Manuel, Lieske, Leonard-Alexander, Ortiz, Ricardo, Fatayer, Shadi, Ronevi, Igor, Albrecht, Florian, Frederiksen, Thomas, Pea, Diego, Gross, Leo

Issue&Volume: 2024-02-08

Abstract: Indenofluorenes are non-benzenoid conjugated hydrocarbons that have received great interest owing to their unusual electronic structure and potential applications in nonlinear optics and photovoltaics. Here we report the generation of unsubstituted indeno[1,2-a]fluorene on various surfaces by the cleavage of two C–H bonds in 7,12-dihydroindeno[1,2-a]fluorene through voltage pulses applied by the tip of a combined scanning tunnelling microscope and atomic force microscope. On bilayer NaCl on Au(111), indeno[1,2-a]fluorene is in the neutral charge state, but it exhibits charge bistability between neutral and anionic states on the lower-workfunction surfaces of bilayer NaCl on Ag(111) and Cu(111). In the neutral state, indeno[1,2-a]fluorene exhibits one of two ground states: an open-shell π-diradical state, predicted to be a triplet by density functional and multireference many-body perturbation theory calculations, or a closed-shell state with a para-quinodimethane moiety in the as-indacene core. We observe switching between open- and closed-shell states of a single molecule by changing its adsorption site on NaCl.

DOI: 10.1038/s41557-023-01431-7

Source: https://www.nature.com/articles/s41557-023-01431-7