Theoretical studies of pi-pi interactions on several dimers of curved polycyclic aromatic systems have been carried out. In the first part, dispersion corrected density functional theory methods (DC-DFT) were used to evaluate the basis set superposition errors (BSSE) in dispersion interactions of the corannulene dimer, and the accuracy of the calculations using DC-DFT methods was compared with high level benchmark calculations. In these calculations, Grimme’s B97D DC-DFT method provided reasonably accurate results with the benchmark calculations. In addition, BSSE obtained with the B97D method along with cc-pVQZ basis set was negligible. Furthermore, a series of calculations were carried out to obtain the pi-pi interaction energy and most stable conformation for the sumanene dimer system. In these calculations, Grimme’s B97D method was used. The potential energy minimum of the sumanene dimer was determined as the concave-convex stacked arrangement with one monomer unit rotated to 60°. The binding energy of the dimer was found to be 19.34 kcal/mol with a 3.72 angstrom distance between two monomer units. Dimers of three different heterosumanenes along with the parent sumanene were also studied. In this set of calculations, two different concave-convex dimer motifs were chosen, eclipsed and staggered (60° rotated). For all the heterosumanenes, as well as the parent sumanene, the staggered conformation is the most stable geometry. The parent sumanene had the highest binding energy. The –NH substituted sumanene produced the second highest binding energy, while the –O analog was the weakest bonded dimer. Finally, dispersion calculations were carried out for the planar aromatic compound of triphenylene. The pi-system of the dimer was distorted by rotating one monomer unit around the principle axis and parallel displacing one monomer unit relative to the other one. Among the rotational dimers, the 39° rotated dimer was the minimum energy conformation. Interaction energy of that dimer was 14.42 kcal/mol with 3.40 angstrom separation between monomers at the B97D/cc-pVQZ level. The parallel displaced minimum energy dimer has a binding energy about 1.0 kcal/mol smaller than the rotational minimum energy geometry.

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Les nucléolipides sont des molécules amphiphiles dont la structure bio-inspirée dérive de celle des acides nucléiques. Leur auto-assemblage en milieu aqueux aboutit à la formation d’objets supramoléculaires de morphologies et structures très diverses. La morphologie a été caractérisée par des techniques complémentaires de microscopie optique et de diffusion de la lumière, tandis que leur structure a été déterminée par la diffusion des rayons X. Il a ainsi été mis en évidence l’existence et le rôle fondamental des interactions faibles entre têtes polaires, au sein des auto-assemblages. La nature de ces interactions faibles a été déterminée par des techniques de spectroscopies IR et UV. Un premier objectif a été de mettre en évidence l’importance de ces interactions, ainsi que leur corrélation avec d’autres facteurs qui régissent le mécanisme d’auto-assemblage, tels que la nature chimique des amphiphiles, ou la morphologie et la structure des objets supramoléculaires en présence.Par ailleurs, la tête polaire nucléotide permet également d’imaginer la formation d’interactions faibles entre les auto-assemblages et un monobrin d’acide nucléique, à l’image des interactions spécifiques entre bases azotées présentes dans l’ADN. Lors de ce travail, nous nous sommes intéressés à une méthode de vectorisation d’acides nucléiques par des objets eux aussi chargés négativement. Contrairement aux approches classiques, l’interaction électrostatique est ici défavorable et l’association repose alors uniquement sur des interactions faibles spécifiques, estimées en spectroscopie. De façon surprenante, la formation des complexes a pu être mise en évidence par des expériences de diffraction des rayons X et un modèle approprié a permis de proposer des mécanismes de formation des complexes. Les propriétés thermodynamiques des différents complexes formés ont été évaluées par la technique de Calorimétrie à Titration Isotherme (ITC). Un point remarquable a été la mise en évidence systématique de trois types de comportements sur l’ensemble des complexes étudiés en fonction de la nature et de la spécificité des interactions mises en jeu. Ceci nous a ainsi permis de proposer différents mécanismes de formation pour chaque type de complexe observé. / Nucleolipids are amphiphilic molecules which bio-inspired structure derives from nucleic acid structure. Their self-assembling behaviour in aqueous medium leads to the formation of supramolecular objects of very different morphologies and structures. The morphology has been characterized with optical microscopy and light scattering complementary techniques, whereas their structure has been determined with X-ray scattering. Thus the existence and the fondamental role of weak interactions between polar heads inside the self-assemblies have been highlighted. The nature of these weak interactions has been determined with IR and UV spectroscopies techniques. A first objectif has been to highlight the importance of these interactions, as well as the their correlation with other factors which drive the mechanism of self-assembly, such as the chemical nature of amphiphiles or the morphology and structure of the supramolecular objects.Moreover the nucleotide polar hear also allows to imagine the formation of weak interactions between the self-assemblies and a single-stranded nucleic acid, such as those highlighted in DNA. In this work, we found interest in a nucleic acid vectorisation method with negatively charged objects as well. On the contrary of classic approaches, electrostatic interaction was here defavorable and assembling relies only on specific weak interactions, estimated with spectroscopy methods. Surprisingly, complexes formation could be highlighted with X-ray scattering experiments, and an appropriate model has allowed the proposal of mechanisms for the formation of complexes. Thermodynamic properties of the different complexes formed have been evaluated with Isothermal Titration Calorimetry (ITC) technique. A remarkable point was the systematic highlighting of three types of behaviour on the whole set of complexes studied, depending of the nature and the specificity of the weak interactions implied. This led us to different proposals for the mechanism of formation of each type of complex studied.

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