Wang Yu, Hou Jie, Eguchi Keitaro, Nanjo Chihiro, Takaoka Tsuyoshi, Sainoo Yasuyuki, Awaga Kunio, Komeda Tadahiro
Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki-Aza-Aoba, Aoba-Ku, Sendai 980-8578, Japan.
Institute of Multidisciplinary Research for Advanced Materials (IMRAM, Tagen), Tohoku University, 2-1-1, Katahira, Aoba-Ku, Sendai 980-0877, Japan.
ACS Omega. 2020 Mar 17;5(12):6676-6683. doi: 10.1021/acsomega.9b04453. eCollection 2020 Mar 31.
We investigated the structural and electronic/spin configurations of a film of the Co tetrakis(1,2,5-thiadiazole) porphyrazine (CoTTDPz) molecule adsorbed on the Au(111) surface by a scanning tunneling microscope (STM). CoTTDPz has a structure similar to that of the Co phthalocyanine molecule, but the benzene ring of the isoindole of the phthalocyanine molecule is replaced by the pentagon moiety of 1,2,5-thiadiazoles that has an S atom at the apex. We find an ordered molecular lattice with a threefold symmetry where a nearest-neighbor distance of 1.30 nm was measured, which is significantly smaller than that observed for the metal Pc molecule. The unit cell of the lattice contains two molecules that are rotated by 60° relative to each other. With the configuration achieved by this rotation, the neighboring molecules can form a stronger interaction through bonding between the S atom at the apex of one molecule and the N atom of the other (the N atom that is bridging the thiadiazoles). The strong interaction between the molecule and the substrate appears in the spin state examined by the detection of the Kondo resonance, which is formed by the screening of an isolated spin by the conduction electron. Even though the existence of the spin was confirmed for the bulk and thick films of this molecule, no Kondo features are detected for the molecules in the first, second, and third layers of the films. However, the isolated molecule in the third layer showed an intriguing combination of the Kondo feature and an inelastic excitation feature caused by a spin-flip process.
我们通过扫描隧道显微镜（STM）研究了吸附在Au(111)表面的四（1,2,5 - 噻二唑）钴卟啉（CoTTDPz）分子薄膜的结构以及电子/自旋构型。CoTTDPz具有与钴酞菁分子相似的结构，但酞菁分子异吲哚的苯环被1,2,5 - 噻二唑的五边形部分取代，该五边形部分在顶点处有一个S原子。我们发现了一种具有三重对称性的有序分子晶格，测得其最近邻距离为1.30 nm，这明显小于金属酞菁分子所观察到的距离。晶格的晶胞包含两个相对于彼此旋转60°的分子。通过这种旋转实现的构型，相邻分子可以通过一个分子顶点处的S原子与另一个分子的N原子（连接噻二唑的N原子）之间的键合形成更强的相互作用。分子与衬底之间的强相互作用出现在通过检测近藤共振所研究的自旋状态中，近藤共振是由传导电子对孤立自旋的屏蔽形成的。尽管已证实该分子的体相和厚膜存在自旋，但对于薄膜的第一、第二和第三层中的分子未检测到近藤特征。然而，第三层中的孤立分子表现出近藤特征与自旋翻转过程引起的非弹性激发特征的有趣组合。
