Structural, Electronic, and Magnetic Properties of Cobalt Tetrakis (Thiadiazole) Porphyrazine Molecule Films on Au(111)

Yu Wang; Jie Hou; Keitaro Eguchi; Chihiro Nanjo; Tsuyoshi Takaoka; Yasuyuki Sainoo; Kunio Awaga; Tadahiro Komeda

doi:10.1021/acsomega.9b04453

Structural, Electronic, and Magnetic Properties of Cobalt Tetrakis (Thiadiazole) Porphyrazine Molecule Films on Au(111)

ACS Omega. 2020 Mar 17;5(12):6676-6683. doi: 10.1021/acsomega.9b04453. eCollection 2020 Mar 31.

Authors

Yu Wang^{1

2}, Jie Hou^{1

2}, Keitaro Eguchi³, Chihiro Nanjo³, Tsuyoshi Takaoka^{1

2}, Yasuyuki Sainoo^{1

2}, Kunio Awaga³, Tadahiro Komeda²

Affiliations

¹ Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki-Aza-Aoba, Aoba-Ku, Sendai 980-8578, Japan.
² Institute of Multidisciplinary Research for Advanced Materials (IMRAM, Tagen), Tohoku University, 2-1-1, Katahira, Aoba-Ku, Sendai 980-0877, Japan.
³ Department of Chemistry & Research Center for Materials Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan.

Abstract

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.