Two-Dimensional Structure Control by Molecular Width Variation with Metal Coordination
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- 作者：Yoshihiro Kikkawa ; Emiko Koyama ; Seiji Tsuzuki ; Kyoko Fujiwara ; Koji Miyake ; Hideo Tokuhisa ; Masatoshi Kanesato
- 刊名：Langmuir
- 出版年：2006
- 出版时间：August 1, 2006
- 年：2006
- 卷：22
- 期：16
- 页码：6910 - 6914
- 全文大小：486K
- 年卷期：v.22,no.16(August 1, 2006)
- ISSN：1520-5827
文摘
The self-assembled monolayer of bipyridine derivative 1, which has two alkyl chains on each end, at the HOPG/1-phenyloctane interface was studied by in situ scanning tunneling microscopy (STM). The detailed mechanism ofa spontaneous change in the monolayer packing pattern by Pd coordination was studied. Uncomplexed 1 existed ina bent form in the monolayer, and the alkyl chains were interdigitated, whereas Pd-complexed 1 was in a straightform and the alkyl chains were not interdigitated. An intermediate state of 1 was successfully observed during metalcoordination. The structure was the bent form with noninterdigitated alkyl chains. Equilibrium intermolecular distancesreported from ab initio calculations indicate that the molecular width of the central aromatic part of uncomplexed 1(7.5 Å) is substantially smaller than that of the peripheral alkyl chain part (9.2 Å). The bent form was suitable forcovering up the surface to maximize the packing density. However, the molecular width of the aromatic unit ofPd-complexed 1 (9.1 Å) was almost identical to that of the alkyl chain unit (9.2 Å). Therefore, Pd-complexed 1 tookthe straight form in the monolayer. The observation of surface coverage by STM suggests that the bent form increasesthe packing density by as much as 16% compared with that of the straight form. These results indicate that the controlof molecular width can be used to design molecular templates for nanostructure formation.