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Novel porphyrinoids, 15. Syntheses of novel expanded [26]porphyrins with conformational control by the “helical effect”
Author(s) -
Franck Burchard,
n Ansgar,
Fuchs Klaus,
Gosmann Martin
Publication year - 1994
Publication title -
liebigs annalen der chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0170-2041
DOI - 10.1002/jlac.15619940510
Subject(s) - chemistry , pyrrole , steric effects , chromophore , aromaticity , porphyrin , dehydrogenation , photochemistry , selectivity , stereochemistry , proton nmr , molecule , organic chemistry , catalysis
Novel [26]porphyrinogens [2] 24–28 were conveniently prepared in few steps from the pyrrole building blocks 19–23 . The selectivity of the cyclization is explained by a conformational helical effect due to steric congestion of the pyrrole β‐substituents. The aromaticity of the [26]porphyrins [2] 30–33 , obtained by dehydrogenation of the porphyrinogens, is evident from the 1 H‐NMR spectra displaying 25‐ppm shift differences for the inner and outer protons of the porphyrins. These pigments belong to the most intensive chromophores known so far, showing VIS absorptions at 544–550 nm with lg ϵ values up to 5.9.