Spirobifluorenyl-porphyrins and their derived polymers for homogeneous or heterogeneous catalysis

Abstract

Decorating porphyrin cores at their meso positions by one, two or four 9,9'-Spirobifluorenyl (SBF) units is an interesting design strategy to obtain efficient and recyclable heterogeneous catalysts for various chemical reactions. The synthesis of metalloporphyrin polymers (RuIICO, FeIIICl, MnIIICl) is easily performed along anodic oxidation of their related monomers or along copolymerization of their monomers in presence of 9,9'-SBF. The efficiency of this polymerization mainly depends on the number of SBF units around the porphyrin cores and on the nature of the metal ion within the porphyrin ligand. Polymer catalysts in heterogeneous phase appear as efficient as the monomer catalysts in homogeneous phase. The main interest of catalysis with polymers is that they can be very easily separated from the reaction medium after reaction by a simple filtration and that they can be washed and reused without loss of their activity. The recyclability of metalloporphyrins polymers is of high interest in the field of catalysis. For asymmetric catalysis, recyclable chiral polymetalloporphyrins based on the SBF scaffold are also of high interest. The chirality may be introduced either by the dimethanoanthracenyl (DMA) units linked to SBF units (acting as electropolymerizable entities) or by a chiral SBF fragment which can be electropolymerizable. Compared to other porphyrin immobilization processes, anodic oxidation is hence a relatively easy tool as the polymer is directly obtained on the anode surface, easily separated under its insoluble form and directly usable as recyclable catalyst for many chemical reactions.