Mishra Shantanu, Beyer Doreen, Eimre Kristjan, Liu Junzhi, Berger Reinhard, Gröning Oliver, Pignedoli Carlo A, Müllen Klaus, Fasel Roman, Feng Xinliang, Ruffieux Pascal
nanotech@surfaces Laboratory , Empa - Swiss Federal Laboratories for Materials Science and Technology , 8600 Dübendorf , Switzerland.
Faculty of Chemistry and Food Chemistry, and Center for Advancing Electronics Dresden , Technical University of Dresden , 01069 Dresden , Germany.
J Am Chem Soc. 2019 Jul 10;141(27):10621-10625. doi: 10.1021/jacs.9b05319. Epub 2019 Jun 28.
The electronic and magnetic properties of nanographenes strongly depend on their size, shape and topology. While many nanographenes present a closed-shell electronic structure, certain molecular topologies may lead to an open-shell structure. Triangular-shaped nanographenes with zigzag edges, which exist as neutral radicals, are of considerable interest both in fundamental science and for future technologies aimed at harnessing their intrinsic high-spin magnetic ground states for spin-based operations and information storage. Their synthesis, however, is extremely challenging owing to the presence of unpaired electrons, which confers them with enhanced reactivity. We report a combined in-solution and on-surface synthesis of π-extended triangulene, a non-Kekulé nanographene with the structural formula CH, consisting of ten benzene rings fused in a triangular fashion. The distinctive topology of the molecule entails the presence of three unpaired electrons that couple to form a spin quartet ground state. The structure of individual molecules adsorbed on an inert gold surface is confirmed through ultrahigh-resolution scanning tunneling microscopy. The electronic properties are studied via scanning tunneling spectroscopy, wherein unambiguous spectroscopic signatures of the spin-split singly occupied molecular orbitals are found. Detailed insight into its properties is obtained through tight-binding, density functional and many-body perturbation theory calculations, with the latter providing evidence that π-extended triangulene retains its open-shell quartet ground state on the surface. Our work provides unprecedented access to open-shell nanographenes with high-spin ground states, potentially useful in carbon-based spintronics.
纳米石墨烯的电学和磁学性质强烈依赖于它们的尺寸、形状和拓扑结构。虽然许多纳米石墨烯呈现闭壳层电子结构，但某些分子拓扑结构可能导致开壳层结构。具有锯齿形边缘的三角形纳米石墨烯以中性自由基形式存在，在基础科学以及旨在利用其固有高自旋磁基态进行自旋操作和信息存储方面的未来技术中都备受关注。然而，由于存在未成对电子，赋予它们更高的反应活性，其合成极具挑战性。我们报道了一种结合溶液法和表面法的π-扩展三角烯的合成方法，π-扩展三角烯是一种非凯库勒纳米石墨烯，化学式为CH，由十个苯环以三角形方式稠合而成。该分子独特的拓扑结构导致存在三个未成对电子，它们耦合形成自旋四重态基态。通过超高分辨率扫描隧道显微镜确认了吸附在惰性金表面的单个分子的结构。通过扫描隧道谱研究了其电子性质，其中发现了自旋分裂单占据分子轨道的明确光谱特征。通过紧束缚、密度泛函和多体微扰理论计算获得了对其性质的详细洞察，后者提供了证据表明π-扩展三角烯在表面上保留其开壳层四重态基态。我们的工作为具有高自旋基态的开壳层纳米石墨烯提供了前所未有的研究途径，可能在碳基自旋电子学中有用。
