Physik Department E20, Technische Universität München , Garching D-85748, Germany.
Institute of Nanotechnology, Karlsruhe Institute of Technology , Eggenstein-Leopoldshafen D-76344, Germany.
ACS Nano. 2017 Feb 28;11(2):1347-1359. doi: 10.1021/acsnano.6b06114. Epub 2017 Jan 31.
We report on the surface-guided synthesis of a dinuclear organocobalt complex, its self-assembly into a complex nanoarchitecture, and a single-molecule level investigation of its switching behavior. Initially, an organic layer is prepared by depositing hexakis((trimethylsilyl)ethynyl)-benzene under ultrahigh-vacuum conditions onto Ag(111). After Co dosage at 200 K, low-temperature scanning tunneling microscopy (STM) reveals an epitaxy-mediated organization mechanism of molecules and on-surface formed organometallic complexes. The dinuclear complexes contain two bis(η-alkynyl) π-tweezer motifs, each stabilizing a single Co atom and express two enantiomers due to a conformation twist. The chirality is transferred to the two-dimensional architecture, whereby its Co adatoms are located at the corners of a 3.4.6.4 rhombitrihexagonal tessellation due to the systematic arrangement and anchoring of the complexes. Extensive density functional theory simulations support our interpretation of an epitaxy-guided surface tessellation and its chiral character. Additionally, STM tip-assisted manipulation experiments on isolated dinuclear complexes reveal controlled and reversible switching between the enantiomeric states via inelastic electron processes. After activation by bias pulses, structurally modified complexes display a distinctive Kondo feature attributed to metastable Co configurations.
我们报告了一种双核有机钴配合物的表面导向合成、其自组装成复杂纳米结构以及对其开关行为的单分子水平研究。首先，通过在超高真空条件下将六(三甲基硅基)乙炔基苯沉积在 Ag(111)上制备有机层。在 200 K 下进行 Co 剂量处理后，低温扫描隧道显微镜（STM）揭示了分子的外延介导组织机制和表面形成的有机金属配合物。双核配合物包含两个双（η-炔基）π-夹钳基序，每个基序稳定一个 Co 原子，并由于构象扭曲而表达两种对映异构体。手性被转移到二维结构中，由于配合物的系统排列和锚固，其 Co adatoms 位于 3.4.6.4 菱形三角六边形的角上。广泛的密度泛函理论模拟支持我们对外延引导的表面细分及其手性特征的解释。此外，对孤立双核配合物的 STM 针尖辅助操纵实验表明，通过非弹性电子过程可以在对映异构体状态之间进行可控和可逆的切换。在偏压脉冲的激活下，结构修饰的配合物显示出独特的 Kondo 特征，归因于亚稳态 Co 构型。
