On the way to new fullerene-based materials

Regio- and stereoselective tether-directed remote functionalization was used to prepare three-dimensional building blocks for supramolecular construction and advanced materials. A C-60-ionophore conjugate was prepared selectively as trans-1 regioisomer in a K+-templated Bingel addition of a bismalonate derived from dibenzo[18]crown-6. It can act as an ion sensor and the close proximity of complexed potassium ions to the fullerene sphere induces anodical shifts in the redox potentials of the latter. A similar but even more pronounced effect is seen in a C-70 cage which is sandwiched between two crown ethers. Favorable C-60-porphyrin ground state interactions were detected by steady-state and time-resolved absorption and luminescence spectroscopy of a trans-1 type, doubly bridged dyad as well as in a fullerene connected to two porphyrins by single linkages. In toluene, both the zinc-porphyrin- and the fullerene-centered excited states are deactivated to a lower-lying charge-transfer (CT) state which emits in the infrared (IR) spectral region. Enantiopure bis-adducts of C-60 with the chiral cis-3 functionalization pattern were prepared by regio- and stereoselective Bingel macrocyclizations using non-racemic chiral tethers. Configurational assignment was possible by a combination of computational and H-1 NMR-spectroscopic conformational analysis and it was confirmed by a comparison of its circular dichroism (CD) spectra with the measured and calculated spectra of another C-60 adduct with the same pi-chromophore. Finally, a polysiloxane-supported fullerene derivative was prepared and proven to act as a heterogeneous sensitizer for the selective photooxidation of sulfides to sulfoxides by O-1(2).