title: A flexible porphyrin-annulene hybrid: a nonporphyrin conformation for meso-tetraaryldivacataporphyrin.
abstract: An annulene-porphyrin hybrid, the diaaza-deficient porphyrin 5,10,15,20-tetraaryl-21,23-divacataporphyrin, has been synthesized by an extrusion of tellurium atom(s) from 5,10,15,20-tetraaryl-21,23-ditelluraporphyrin under treatment with HCl. In addition, a monoaza-deficient 5,10,15,20-tetraaryl-21-tellura-23-vacataporphyrin was formed in the same reaction. The two new members of the vacataporphyrin family were characterized by X-ray crystallography, as well as UV/Vis and NMR spectroscopy. These aromatic molecules preserve the fundamental structural and spectroscopic features of the parent tetraarylporphyrin. The X-ray crystal structures of 21,23-divacataporphyrin and 21-tellura-23-vacataporphyrin show typical porphyrin patterns. The molecules are not strictly planar and show distortion of the annulene moieties. The N22⋅⋅⋅N24 distances (5.23 and 5.09 Å) are considerably longer than in regular porphyrins. For 21,23-divacataporphyrin, variable-temperature (1)H NMR spectroscopy data allowed the identification of divacataporphyrin stereoisomers differentiated by the geometry of the butadiene bridges. The forms remain in thermodynamic equilibrium.
authors.affiliation: Department of Chemistry, University of Wrocław ul. F.Joliot-Curie 14, 50-383 Wrocław, Poland.
authors.forename: Ewa
authors.initials: E
authors.lastname: Pacholska-Dudziak
authors.forename: Ludmiła
authors.initials: L
authors.lastname: Szterenberg
authors.forename: Lechosław
authors.initials: L
authors.lastname: Latos-Grażyński