Supramolecular Subphthalocyanine Cage as Catalytic Container for the Functionalization of Fullerenes in Water

Herein we report the first example of a supramolecular cage that works as a catalytic molecular reactor to perform transformations over fullerenes in aqueous medium. Taking advantage of the ability of metallo-organic Pd(II)-subphthalocyanine (SubPc) capsules to form stable host:guest complexes with C60, we have prepared a water-soluble cage that provides a hydrophobic environment for conducting cycloadditions over encapsulated C60, namely, Diels-Alder reactions with anthracene. Indeed, the presence of catalytic amounts of SubPc cage dissolved in water promotes co-encapsulation of insoluble C60 and anthracene substrates, allowing the reaction to occur inside the cavity under mild conditions. The lower stability of the host:guest complex with the resulting C60 cycloadduct facilitates its displacement by pristine C60, which grants catalytic turnover. Moreover, bis-addition compounds are regioselectively formed inside the cage when using excess anthracene. A metallo-organic Pd(II)-subphthalocyanine cage has been shown to catalyze the Diels-Alder reaction between C60 and anthracene in water to yield mono- and bis-adducts with high regioselectivity. Catalytic amounts of the cage led to better conversions because it favours co-encapsulation of the substrates in the hydrophobic cavity. Moreover, the larger binding affinity of the cage for C60 compared to the resulting adducts enables catalytic turnover.+image

Automated summary

This study introduces a supramolecular cage that acts as a catalytic molecular reactor for transformations over fullerenes in aqueous medium. The cage, based on metallo-organic Pd(II)-subphthalocyanine, facilitates Diels-Alder reactions between C60 and anthracene with high regioselectivity. Catalytic turnover is achieved by the lower stability of the host:guest complex with the resulting C60 cycloadduct, allowing for better conversions in the hydrophobic environment provided by the cage.