Chiral Ordering and Conformational Dynamics for a Class of Oligo-phenylene-ethynylenes on Au(111)
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- 作者：Carsten Busse ; Sigrid Weigelt ; Lars Petersen ; Erik Læ ; gsgaard ; Flemming Besenbacher ; Trolle R. Linderoth ; Anne H. Thomsen ; Morten Nielsen ; Kurt V. Gothelf
- 刊名：Journal of Physical Chemistry B
- 出版年：2007
- 出版时间：May 31, 2007
- 年：2007
- 卷：111
- 期：21
- 页码：5850 - 5860
- 全文大小：1374K
- 年卷期：v.111,no.21(May 31, 2007)
- ISSN：1520-5207
文摘
Adsorption structures formed from a class of planar organic molecules on the Au(111) surface under ultrahighvacuum conditions have been characterized using scanning tunneling microscopy (STM). The molecules havedifferent geometries, linear, bent, or three-spoke, but all consist of a conjugated aromatic backbone formedfrom three or four benzene rings connected by ethynylene spokes and functionalized at all ends with analdehyde, a hydroxyl, and a bulky tert-butyl group. Upon adsorption, the molecules adopt different surfaceconformations some of which are chiral. For the majority of the observed adsorption structures, chirality isexpressed also in the molecular tiling pattern, and the two levels of chirality display a high degree of correlation.The formation and chiral ordering of the self-assembled structures are shown to result from dynamicinterchanges between a diffusing lattice gas and the nucleated islands, as well as from a chiral switchingprocess in which molecules alter their conformation by an intramolecular rotation around a molecular spoke,enabling them to accommodate to the tiling pattern of the surrounding molecular structures. The kinetics ofthe conformational switching is investigated from time-resolved, variable temperature STM, showing theprocess to involve an activation energy of ~0.3 eV depending on the local molecular environment. Themolecule-molecule interactions appear primarily to be of van der Waals character, despite the investigatedcompounds having functional moieties capable of forming intermolecular hydrogen bonds.