Polybenzyl ether dendrimers for the complexation of [60]fullerenes

The formation of host-guest complexes between C(60) and polybenzyl ether dendrimers with different central cores (phloroglucinol, meso-tetraphenylporphyrin, cyclotriveratrylene) has been investigated in organic solvents by means of (13)C-NMR and UV-Vis spectroscopy. The interior of the dendrimers with a phloroglucinol core provides the correctly sized space for the inclusion of [60]fullerene and (13)C-NMR studies suggest that the guest resides near the central core. In the dendrimers containing a meso-tetraphenylporphyrin (TPP) core, the absorbance of the porphyrin Soret band is substantially reduced in the presence of [60]fullerene, thus providing evidence for close vicinity of the fullerene guest to the central core. In solution, the cyclotriveratrylene (CTV) unit alone is a poor receptor for fullerene, but its functionalization with polybenzyl ether dendrons affords an internal cavity with a more appropriate shape and dimension, thus allowing complexation. Indeed, the K(a) values (order of magnitude 10¹-10² L mol^-1) increase significantly with the generation number of the surrounding dendritic substituents.