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Nowadays, functionalized interfaces appear as a promising way for nanotechnologies. The deposition and control of organic molecules on semi-conducting surfaces is therefore a challenge. The C3-symmetrical compounds based on 1,3,5-triazine core are well-known in diverse areas of chemistry because they exhibit enhanced physical properties, such as optical nonlinearities or electronic conductivities and they find useful applications in coordination chemistry and crystal engineering. We have developed a new method to synthesize 2,4,6-tri(2’-thienyl)-1,3,5-triazine with good yield. These molecules have been successfully deposited on semiconductor surface at room temperature under ultra high vacuum. For this, we have used an original SiB(111)-√3x√3 surface, known to be less reactive than another Si reconstructions.
The high resolution STM images show that two of the three thienyl moieties of 2,4,6-tri(2’-thienyl)-1,3,5-triazine are adsorbed on top of two Si atoms of the √3x√3 reconstruction. We have determined the density of state (DOS) around the molecule and the HOMO and LUMO energy levels by DFT calculations (Wien2k code). The 3D representations of these molecular densities and their comparisons with the SiB(111) DOS show that (i) the distance between two thienyl groups is in good agreement with the length of the largest diagonal of √3x√3 structure and (ii) the molecular DOS is maximal on the thienyl moieties. These results corroborate the STM observations.
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