Synthesis, Caharacterization, and Electronic Properties of Metalloporphyrins Annulated to Exocyclic Imidazole and Imidazolium Rings

Full paper; International audience; meso-Tetraarylporphyrin complexes (M = Ni, Cu, Zn, H2) fused to an imidazole ring across two neighboring β-pyrrolic positions were synthesized through a cyclization reaction between β,β'-diaminoporphyrins and formic acid or trimethyl orthoformate under acidic conditions. Two synthetic procedures were used to obtain the corresponding porphyrin N,N'-dimethylimidazolium salts derivatives: alkylation of the imidazole nitrogen atoms with iodomethane and the cyclization reaction between the porphyrin bearing two neighboring β-N-methyl groups and trimethyl orthoformate in the presence of ammonium hexafluorophosphate. The electrochemical properties of these porphyrins annulated to an imidazole/imidazolium ring have been investigated by cyclic and rotating disk voltammetry.