Laboratoire Léon Brillouin
UMR12 CEA-CNRS, Bât. 563 CEA Saclay
91191 Gif sur Yvette Cedex, France
In collaboration with
Extended planar aromatic systems represent attractive targets as active materials in electronic devices. Some of them are also commonly used in biology to achieve structure-specific recognition of DNA through p-p overlapping of nucleic bases. In order to achieve their self-organization in solution or the solid state it is therefore essential to tailor them properly. From this viewpoint, planar conjugated molecules having a threefold symmetry and bearing long alkyl chains are of particular interest because they behave as liquid crystals.
We report here on the synthesis and 2D self-assembly of 2,8,14-trimethyl-5,11,17-triazatrinaphthylene (Figure 1), the first member of a novel family of C3h-symmetry conjugated compounds noted TrisK by analogy with the celtic symbol Triskele meaning “three-legged”. The molecule of TrisK consists in a central benzene ring with three peripheral branches made of quinoline moieties, each of them terminated by a methyl group. The relative positions of the three nitrogen atoms and of the three methyl groups on the same side of each branch (clockwise and counter-clockwise respectively) make TrisK a prochiral molecule exhibiting two enantiotopic faces.
Figure 2: STM image (20.2×20.2 nm2, Ut=177 mV, It=12 pA) of a self-organized domain of TrisK at the n-tetradecane/Au(111) interface
Following the description of its chemical synthesis, we show here that compound TrisK forms long range self-assembled monolayers (SAMs) with hexagonal packing on HOPG and that high resolution STM reveals the presence of a high contrast adsorption site on one of its three branches (Figure 2). This intramolecular non-equivalent adsorption site is very surprising for a highly symmetrical molecule and is interpreted in terms of a strong local electronic interaction between certain atoms of the molecule and those of graphite. Beside, ab-initio calculations show that a purely molecular contribution may also be involved.
The large aromatic surface of TrisK makes them potentially interesting as neutral precursors of nucleic acid binders, a route which is currently under investigation in the framework of the PhD thesis of Ms. Hélène Bertrand.
Triazatrinaphthylene, a three-fold symmetry planar conjugated system with two-dimensional self-assembly properties
N. Saettel, N. Katsonis, A. Marchenko, M-P. Teulade-Fichou, and D. Fichou, J. Mater. Chem. 15, 3175-3180 (2005).
• Synthèse et caractérisation des nano-objets / Synthesis and characterization of nano-objects › From molecules to molecular materials Future optics and electronics › Organic and molecular electronics
• Service de Physique et Chimie des Surfaces et des Interfaces
• Laboratoire d'Electronique et Photonique Organique (LEPO) • pas de titre