Institute of Multidisciplinary Research for Advanced Materials-IMRAM, Tagen, Graduate School of Science, Tohoku University, 2-1-1 Katahira, Aoba-Ku, Sendai 980-0877, Japan.
ACS Nano. 2013 Feb 26;7(2):1092-9. doi: 10.1021/nn304035h. Epub 2013 Feb 5.
By using scanning tunneling microscopy (STM), we studied the heteroleptic double-decker complex TbNPcPc (NPc = naphthalocyaninato and Pc = phthalocyaninato), where two different planar ligands sandwich a Tb(III) ion and an unpaired π electron causes Kondo resonance upon adsorption on the Au(111) surface. Kondo resonance is a good conductance control mechanism originating from interactions between conduction electrons and a localized spin. Two types of adsorption geometries appear depending on which side contacts the substrate surface, which we call Pc-up and NPc-up molecules. They make intriguing molecular assemblies by segregation. In addition, different adsorption geometries and molecular assemblies provide a variety of spin and electronic configurations. Pc-up and NPc-up molecules both showed the Kondo resonance when they were isolated from other molecules, but their Kondo temperatures were different. A one-dimensional chain composed of only NPc-up molecules was found, in which the dI/dV plot showed a conversion from the Kondo peak to a dip at the Fermi energy. In addition, a two-dimensional lattice with an ordering of Pc-up and NPc-up molecules in an alternative manner was observed, in which no Kondo peak was detected in the molecule. The absence of the Kondo peak was accounted for by the change of azimuthal rotational angle of the two ligands of both molecules. The results imply that a molecule design and adsorption configuration tailoring can be used for the spin-mediated control of the electronic conductance of the molecule.
我们使用扫描隧道显微镜（STM）研究了异双核双层配合物 TbNPcPc（NPc = 萘酞菁基和 Pc = 酞菁基），其中两个不同的平面配体夹在 Tb（III）离子和一个未配对的π电子之间，当吸附在 Au（111）表面时会引起 Kondo 共振。Kondo 共振是一种良好的电导控制机制，源于传导电子与局域自旋之间的相互作用。根据与基底表面接触的是哪一侧，会出现两种吸附几何形状，我们称之为 Pc-up 和 NPc-up 分子。它们通过隔离形成有趣的分子组装。此外，不同的吸附几何形状和分子组装提供了多种自旋和电子构型。当 Pc-up 和 NPc-up 分子彼此隔离时，它们都表现出 Kondo 共振，但它们的 Kondo 温度不同。我们发现，只有 NPc-up 分子组成的一维链，在其 dI/dV 图中，Kondo 峰转换为费米能级处的凹陷。此外，还观察到以交替方式排列的 Pc-up 和 NPc-up 分子的二维晶格，其中分子中没有检测到 Kondo 峰。两个分子的两个配体的方位旋转角度的变化解释了 Kondo 峰的缺失。结果表明，分子设计和吸附构型的调整可用于自旋介导的分子电子电导的控制。
