Functionalized porphyrins from meso-poly-halogeno-alkyl-dipyrromethanes: synthesis and characterization

Abstract

Starting from pyrrole-carbinol derivatives, a set of three optimized experimental conditions was used to prepare six dipyrromethanes (DPM) bearing meso-poly-halogeno-alkyl chains. On the one hand, the condensation of $p$-anisaldehyde and the DPMs bearing a perfluoroalkyl chain (CF3, C3F7 or C7F15) produced, after oxidation, the expected trans-A2B2-porphyrins in reasonable yields. On the other hand, 5,15-diformyl-10,20-diarylporphyrin was directly obtained starting from the meso-(dichloromethyl)dipyrromethane, while traces of an unprecedented porphyrin bearing two meso-acyl fluoride groups were isolated from the use of the meso-(chlorodifluoromethyl)dipyrromethane. The straightforward formation of bis-formyl porphyrins is competitive compared to previously reported methods and has been extended to other benzaldehydes. The electron-withdrawing character of the different substituents appended to porphyrins is enlightened through a combination of photophysical, electrochemical, structural and theoretical studies.

Keywords

• Dipyrromethanes
• Porphyrins
• Formylation
• Acyl fluoride
• Photophysics