<i>meso</i>-Tetrakis(pentafluorophenyl)porphyrin-Derived Chromene-Annulated Chlorins

Abstract

The synthesis of mono- and bis-chromene-annulated <i>meso</i>-(pentafluorophenyl)­chlorins from <i>meso</i>-tetrakis­(pentafluorophenyl)­porphyrins by an OsO₄-mediated dihydroxylation reaction, followed by an intramolecular nucleophilic aromatic substitution reaction, is described. The reaction sequence is applicable to the free base systems as well as their Zn­(II), Ni­(II), Pd­(II), and Pt­(II) complexes. The optical properties (UV–vis and fluorescence spectra) of the (metallo)­chlorin-like chromophores that possess slightly red-shifted optical spectra compared to the corresponding 2,3-dihydroxychlorins are reported. Molecular modeling and ¹H–¹⁹F-HOESY NMR spectroscopy provide indications for the conformation of the chromene-annulated chromophores. Using ¹H–¹H COSY and ¹⁹F–¹⁹F QF-COSY NMR spectra, we interpret the ¹H and ¹⁹F NMR spectra of the porphyrins and chlorins, thus providing a refined reference point for the use of ¹⁹F NMR spectroscopy as a diagnostic tool in the analysis of <i>meso</i>-pentafluorophenyl-substituted porphyrinoids