Synthesis and applications of large supramolecular nanocapsulesmatryoshka-type masks, higher fullerene C84 purification and stabilization of metallic clusters and sub-nanoparticles

Resumen

The development of supramolecular assemblies with big cavities is important to recognize specific guests or infer a chemo- or regioselective chemistry, in analogy to natural enzymes. The objective of this thesis was to design, synthesize and characterize new 3D supramolecular nanocapsules bearing large cavities to use them in different applications. Four new self-assembled nanocapsules were developed by self-assembly of Zn-TCPP with pTp or ppp (diarylalkyne- or terphenyl-based) macrocyclic ligands complexed with Pd or Cu, which lead to two different cavity sizes depending on the selected ligand. Then, host-guest studies for each nanocapsule were performed with different guests including fullerene-C60, the C60⸦[10]CPP complex, higher fullerenes and the azafullerene-(C59N)2. Furthermore, the synthesis of metallic nanoparticles was investigated in the presence of supramolecular nanocapsules. First, a matryoshka-like assembly was synthesized by encapsulating the C60⸦[10]CPP complex in the pTp-based tetragonal prismatic nanocapsule. This new system showed strong host-guest assembly only when the three components were present. The synergistic effect of the tetragonal prismatic nanocapsule and the nanohoop [10]CPP molecule severely limited the exposed surface of the entrapped C60 and led to the regioselective formation of trans-3 bis-adduct under Bingel cyclopropanation conditions. The combination of XRD, NMR and void analysis afforded a clear understanding on the specific regioselectivity imposed by the supramolecular mask. The trans-3 bis-adduct products were analyzed and characterized by means of HPLC, UV-Vis and NMR. Furthermore, the use of large tetragonal prismatic nanocapsules to selective encapsulate higher fullerenes was investigated. Effective C84 purification directly from fullerene extract soot was demonstrated by using the pTp-based nanocapsule, as ascertained by ESI-MS, HPLC and MALDI-TOF. The affinity of pTp- and ppp-based nanocapsules for other larger fullerenic species such as azafullerene (C59N)2 was studied by UV-Vis titrations. Moreover, competition studies of (C59N)2 and fullerene-C84 with a supramolecular nanocapsule served to determine the association constant of pTp-nanocapsule with C84 and circumvent the poor solubility of the latter. Finally, in the context of developing catalytically-active metallic nanoparticles with large surface/volume ratio, the synthesis of sub-nanometric Ru nanoparticles in the presence of a ppp-based supramolecular nanocapsule was performed. The catalytic properties of this nanoparticles were tested on the hydrogenation of styrene to ethylbenzene, in agreement with the sub-nanometric size of the Ru NPs. Moreover, the encapsulation of clusters of [Ru5] was observed by ESI-MS monitoring, suggesting the trapping of the initial stages of the nucleation process towards nanoparticle formation. DFT studies were performed to determine a plausible structure for [Ru5] clusters and the possible stabilization regions of the nanocapsule.