Odd–Even Effect in the Surface Structure of Alkyloxy-Substituted Anthraquinone on HOPG Observed by Scanning Tunneling Microscope

• Published in: Bulletin of the Chemical Society of Japan Vol. 86; no. 3; pp. 354 - 362
• Main Authors: Tamaki, Yoshinori, Muto, Kosuke, Miyamura, Kazuo
• Format: Journal Article
• Language: English
• Published: The Chemical Society of Japan 15.03.2013
• ISSN: 0009-2673; 1348-0634
• DOI: 10.1246/bcsj.20120283

Self-assembled adlayers of a series of anthraquinone derivatives, 2-alkoxyanthraquinone (n-ant, n = 14, 15, 16, 17, 18, 20, and 22) where n stands for the alkyl (CnH2n+1) chain length, on highly oriented pyrolytic graphite (HOPG) surface are investigated by scanning tunneling microscope (STM). Anthraquinone derivatives are found to form C–H···O hydrogen-bonded dimers. However, the self-assembled 2D pattern of monolayer depends on the parity (odd/even) of carbon atoms and the length of the alkyl chains. When n is even in number, the aggregating structure in the monolayer is interdigitated lamellar structure. The specific feature of these lamellae is the propagation of dislocations. The frequency of dislocation increased as the alkyl chain elongated. However, when n is odd in number, molecules adopt different conformation (type B) and the aggregating structure changes drastically. This indicates that the orientation of the terminal methyl of the alkyl group induces the surface structural change, i.e., the odd–even effect.