Formyl-Porphyrin and Formyl-Fullerenoporphyrin Building Blocks for the Construction of Multiporphyrin Arrays

A fullerene derivative bearing a benzaldehyde unit has been prepared and used as starting material for the synthesis of a formyl-fullerenoporphyrin building block. Condensation of this aldehyde with pyrrole in CHCl3 with BF3 center dot Et2O as catalyst followed by p-chloranil oxidation yielded a pentaporphyrinic scaffold surrounded by four peripheral C-60 subunits. By following a similar strategy, a bis-porphyrin building block bearing an aldehyde function was prepared and used for the construction of a nonaporphyrin array by reaction with pyrrole under typical porphyrin synthesis conditions. Whereas the H-1 NMR spectrum recorded at room temperature for the nonaporphyrin system is well defined, the signals recorded under the same conditions for the pentaporphyrin derivative surrounded by four peripheral C60 groups are broad. Indeed, the C-60-pentaporphyrin ensemble appears as a mixture of conformers which equilibrate slowly on the NMR time scale at room temperature. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)