title: Isoporphycene: The Fourth Constitutional Isomer of Porphyrin with an N(4) Core-Occurrence of E/Z Isomerism.
abstract: Liberation of the ligand from the nickel complex 1 obtained by template synthesis yielded isoporphycene (as the octaethyl derivative 2), the first constitutional isomer of porphyrin with an N(4) core for which E/Z isomerism is involved: Compound 2 is present as the E isomer, which is in rapid, presumably acid-catalyzed equilibrium with a small amount (2 %) of the Z isomer. The remaining unknown constitutional isomers of porphyrin are considerably higher in energy than the already rather labile isoporphycene, so that the latter should mark the border of existence for this type of structural variant of porphyrin.
authors.affiliation: Institut für Organische Chemie der Universität, Greinstrasse 4, D-50939 Köln (Germany).
authors.initials: E
authors.lastname: Vogel
authors.initials: P
authors.lastname: Scholz
authors.initials: R
authors.lastname: Demuth
authors.initials: C
authors.lastname: Erben
authors.initials: M
authors.lastname: Bröring
authors.initials: H
authors.lastname: Schmickler
authors.initials: J
authors.lastname: Lex
authors.initials: G
authors.lastname: Hohlneicher
authors.initials: D
authors.lastname: Bremm
authors.initials: YD
authors.lastname: Wu