Projet de thèse consiste de plusieurs parties:-synthèse de nanographène chirale, caractérisation de ses propriétés photo-physiques (publication en JACS acceptée);-synthèse des astérisques moléculaires, qui combinent les propriétés luminescences du noyau benzène persulfuré et des solubilité aqueuse et biocompatibilité des dendrons avec des branches de PEG; une application de ces dendrons pour couvrir les nanoparticules de silice ;-synthèse des astérisques moléculaires avec noyau de benzène persulfuré et branches des heterocycles, pour explorer leurs auto-assemblage et propriétés chelatantes vers métaux. / The synthesis of molecular asterisks as "smart sensors" with a persulfurated benzene core and various ligands was explored. Asterisks with heteroaromatic ligands were synthesized for exploring their metal ions complexing ability. PEG dendrons were tested for increasing the water solubility of the asterisks, and to verify if PEG asterisks could encapsulate some hydrophobic molecules. The PEG dendrons were synthesized for making smart asterisks sensors, and for another purpose: the coating of silica nanoparticles to prevent their fast degradation in water. Unfortunately, this protection from degradation was ineffective, but we could make PEG asterisks to encapsulate molecules (Nile Red) toward new drug nanocarriers.The synthesis of chiral nanographenes embedding [5]- or [7]helicenes is reported. Usually [5]helicenes are configurationally labile, while higher helicene homologs are stable. We synthesized a stable chiral nanographene with six embedded [5]helicene units (a [5]helicene trimer). We found a strong distortion of benzene rings, especially in the triphenylene core. The enantiomers were separated and the chiroptical properties were measured.The synthesis of [7]helicene trimer was also performed with a great enantio- and diastereoselectivity. When a Ni(0)- mediated cyclotrimerization is achieved with an enantiopure [7]helicene substrate, only one enantiomer of the trimer is obtained, while keeping intact the configuration of the substrate. On a racemic substrate, three diastereomers were obtained. One of them demonstrated the highest values of a benzene ring distortion reported to date (mean puckering angle and twisting angle).