Supramolecular studies on the behaviour of different chiral cycloalkane-based compounds as receptors, gelators and surfactants

Resumo

In this thesis, four different supramolecular systems were studied as receptors, gelators or surfactants. The influence of different structural factors of the single molecule on the final supramolecular properties was analysed. Different strategies were used to prepare the studied compounds. The combination of different techniques leads us to better understand these systems obtaining synergistic results. Results of this thesis are divided in four chapters: 1) Different tripodal anion receptors were synthesised and their complexation with different anions were studied. Using NMR, complexation Gibbs energies were calculated and the binding affinity were studied. Using theoretical calculations, the structure of the complexes were predicted. Also, thermodynamics of the host-guest system were calculated and theoretical calculations lead us to rationalise the experimental results. 2) Three different families of cycloalkane diamide-based gelators were studied to determine the influence of the ring size, the substitutions of the ring and the stereochemistry on the final gelation abilities. Using the tube inversion test and rationalising it with different solubility parameters, the gelation ability was determined. This study was accompanied by high resolution NMR. Self-assembly was studied using theoretical calculations and circular dichroism. Results show that all of the studied gels are chiral despite some of the monomers are meso compounds, in whose symmetry was broken with sonication. Then, using SEM, the morphology of the aggregates was determined. 3) Four different bolaform amphiphiles were synthesised and their behaviour as surfactants were studied to determine the influence of the stereochemistry and the regiochemistry on the final surfactant behaviour. Using the pendant drop method, the variation of the surface tension with the concentration was analysed. We developed a new method to predict the structure of the self-assembled surfactants at the surface. CryoTEM and SAXS were used to determine the morphology and size of the aggregates. 4) In the last chapter, four pH-dependent -amino acid-based surfactants were synthesised. Supramolecular properties of these systems were studied using pendant drop method, cryoTEM, theoretical calculations, different physicochemical titrations, circular dichroism, UV-vis absorption and DLS. These surfactants show interesting acid-base behaviour suitable for biological applications. They have been studied as potential new non-viral vectors for gene therapy using different biophysical and biological techniques. Results show that these surfactants are not toxic and they have interesting features to be used as vectors.