Inverted Porphyrin

meso-Tetraarylporphyrins are most conveniently obtained in acid- catalyzed reactions of pyrrole and aldehydes, termed collectively "Rothemund condensations". In principle such syntheses can lead to a vast number of cyclic and linear oligomerization products, yet for over 50 years tetraarylporphyrins had been the only observed macrocycles.

However, in 1994 a new condensation product was reported independently by our group (P.J. Chmielewski) and the group of H. Furuta. The new compound was named inverted or N-confused porphyrin to emphasize its relationship to the regular porphyrin.

Inverted porphyrins are currently under investigation in a number of research groups worldwide. N-confused porphyrin exhibits an unusual tautomeric equilibirium, which affects its aromaticity, and undergoes several remarkable reactions including substitutions, internal fusion and ring disruption. Especially interesting opportunities open up in the area of coordiation chemistry. N-confused porphyrin coordinates various transition and main-group metals, often forming metal-carbon bonds or stabilizing unusual oxidation states. Complexes of N-confused porphyrin are structurally diverse and often quite reactive, which warrants a rich field for chemical exploration.

Further reading

Chmielewski, P. J.; Latos-Grażyński, L.; Rachlewicz, K.; Głowiak, T. Tetra-p-Tolylporphyrin With an Inverted Pyrrole Ring: A Novel Isomer of Porphyrin. Angew. Chem., Int. Ed. Engl. 1994, 33, 779.

Chmielewski, P. J.; Latos-Grażyński, L. N-Methylporphyrin With an Inverted N-Methyl-Pyrrole Ring. The First Isomer of N-Methyl-Tetraphenylporphyrin. J. Chem. Soc., Perkin Trans. 2 1995, 503.

Chmielewski, P. J.; Latos-Grażyński, L.; Głowiak, T. Reactions of Nickel(II) 2-Aza-21-Carba-5,10,15,20-Tetraphenylporphyrin With Methyl Iodide. The First Structural Characterization of a Paramagnetic Organometallic Nickel(II) Complex. J. Am. Chem. Soc. 1996, 118, 5690.

Chmielewski, P. J.; Latos-Grażyński, L. EPR and 2H NMR Studies on the Oxidation of Nickel(II) 2-Aza-21-Carbatetraphenylporphyrin to Form Novel Organometallic Nickel(III) Complexes. Inorg. Chem. 1997, 36, 840.

Chmielewski, P. J.; Latos-Grażyński, L. Reactions of Nickel(II) 2-Aza-2-Methyl-21-Methyl-21-Carbaporphyrin With Phenyl Grignard Reagent, Phenyllithium and N-Butyllithium. Inorg. Chem. 2000, 39, 5639.

(See the complete publication list of our group.)