Two-Dimensional Self-Assemblies of Thiophene-Fluorenone Conjugated Oligomers on Graphite: A Joint STM and Molecular Modeling Study

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• 作者：Mathieu Linares ; Lorette Scifo ; Renaud Demadrille ; Patrick Brocorens ; David Beljonne ; Roberto Lazzaroni ; Benjamin Grevin
• 刊名：Journal of Physical Chemistry C
• 出版年：2008
• 出版时间：May 1, 2008
• 年：2008
• 卷：112
• 期：17
• 页码：6850 - 6859
• 全文大小：2197K
• 年卷期：v.112,no.17(May 1, 2008)
• ISSN：1932-7455

文摘

The formation of self-assembled monolayers of bithiophene-fluorenone conjugated oligomers, 2,7-bis-(4-octyl-thien-2-yl)-fluoren-9-one (B4OTF) and 2,7-bis-(5-octyl-thien-2-yl)-fluoren-9-one (B5OTF), has beenstudied on highly oriented pyrolitic graphite (HOPG) by scanning tunneling microscopy (STM), with the aimof determining the influence of the molecular structure and conformation on the supramolecular organization.The experimental data are discussed in light of a modeling study of the molecular conformation and theadsorption on graphite using molecular mechanics and molecular dynamics simulations. It is shown thatmolecules with alkyl groups grafted in the C4 position (B4OTF) self-assemble into an anti-anti chiral latticewhich is favored both by dipole-dipole and Van der Waals interactions. The short-range organization appearsmore complex for molecules with alkyl groups grafted in the C5 position (B5OTF). Due to a competitionbetween dipole-dipole and Van der Waals interactions, the modeled assemblies based on syn-syn, syn-anti, and anti-anti B5OTF conformers are all stable and very close in energy, but do not explain the featureof a long-range periodicity evidenced from large-scale STM images. On the basis of the comparative analysisbetween the experimental data and the modeling, it is then suggested that the supramolecular self-assemblyof B5OTF on HOPG implies the presence of several conformers in the monolayer.