On-Surface Synthesis and Characterization of Honeycombene Oligophenylene Macrocycles

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• 作者：Min Chen ; Jian Shang ; Yongfeng Wang ; Kai Wu ; Julian Kuttner ; Gerhard Hilt ; Wolfgang Hieringer ; J. Michael Gottfried
• 刊名：ACS Nano
• 出版年：2017
• 出版时间：January 24, 2017
• 年：2017
• 卷：11
• 期：1
• 页码：134-143
• 全文大小：595K
• ISSN：1936-086X

文摘

We report the on-surface formation and characterization of [30]-honeycombene, a cyclotriacontaphenylene, which consists of 30 phenyl rings (C₁₈₀H₁₂₀) and has a diameter of 4.0 nm. This shape-persistent, conjugated, and unsubstituted hexagonal hydrocarbon macrocycle was obtained by solvent-free synthesis on a silver (111) single-crystal surface, making solubility-enhancing alkyl side groups unnecessary. Side products include strained macrocycles with square, pentagonal, and heptagonal shape. The molecules were characterized by scanning tunneling microscopy and density functional theory (DFT) calculations. On the Ag(111) surface, the macrocycles act as molecular quantum corrals and lead to the confinement of surface-state electrons inside the central cavity. The energy of the confined surface state correlates with the size of the macrocycle and is well described by a particle-in-the-box model. Tunneling spectroscopy suggests conjugation within the planar rings and reveals influences of self-assembly on the electronic structure. While the adsorbed molecules appear to be approximately planar, the free molecules have nonplanar conformation, according to DFT.