Synthesis and characterization of a new porphyrin-fullerene dyad containing a β-pyrrolic linkage

Two new ß-substituted arylethynyl meso-tetraphenylporphyrins, 2[(4'-formyl)phenyl]ethynyl-5,10,15,20-tetraphenylporphyrin (System A) and 2-[(4'-methyl)phenyl]ethynyl-5,10,15,20tetraphenylporphyrin (System B) and their zinc derivatives were synthesized. Comparative UV/Visible and cyclic voltammetry studies of such macrocycles reveal the presence of an extensive conjugation between the tetrapyrrolic ring and the linker, through π-π orbitais interaction. This interaction was observed in form of a "push-pull" effect that moves the electronic charge between the porphyrin and the aldehyde group of the System A. System B, bearing a methyl instead of the formyl group, was synthesized in order to evaluate the effect of the substitution on the charge derealization, which is necessary to corroborate the push-pull mechanism hypothesis. The new porphyrin, System A, was also used as starting material for the synthesis of new porphyrinfullerene dyads in which the [60]fullerene is directly linked to the tetrapyrrolic rings by ethynylenphenylen subunits. Fluorescence and transient absorption measurements of the new dyads reveal that ultrafast energy and electron transfer occur respectively in non polar and polar solvents, with high values of the rate constant. Copyright The Electrochemical Society.