Tetraoxaporphyrin(220.127.116.11) Dication and Tetraoxaporphyrinogens(18.104.22.168) (pages 1151–1153)
Prof. Dr. Gottfried Märkl, Heinrich Sauer, Dr. Peter Kreitmeier, Dr. Thomas Burgemeister, Fritz Kastner, Georg Adolin, Prof. Dr. Heinrich Nöth and Dr. Kurt Polborn
Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199411511
Very flexible and antiaromatic versus relatively rigid and aromatic—that is the difference between porphyrinogen 1 and its oxidation product porphyrin dication 2. Although both compounds occur in the cis, trans, cis, trans configuration, the protons along the inner perimeter of 2 are shifted roughly 20.5 ppm upfield, and the outer protons are shifted approximately 8.4 ppm downfield relative to the corresponding protons in 1.