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

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

Porphyrin-Metalation-Mediated Tuning of Photoredox Catalytic Properties in Metal–Organic Frameworks

Photoredox catalytic activation of organic molecules via single-electron transfer processes has proven to be a mild and efficient synthetic methodology. However, the heavy reliance on expensive ruthenium and iridium complexes limits their applications for scale-up synthesis. To this end, photoactive metal–organic frameworks (MOFs) exhibit unique advantages as novel heterogeneous photocatalytic systems, yet their utilization toward organic transformations has been limited. Here we describe the preparation and synthetic applications of four isostructural porphyrinic MOFs, namely, UNLPF-10a, -10b, -11, and -12, which are composed of free base, In^III-, Sn^IVCl₂-, and Sn^IV-porphyrin building blocks, respectively. We demonstrate that the metalation with high valent metal cations (In^III and Sn^IV) significantly modifies the electronic structure of porphyrin macrocycle and provides a highly oxidative photoexcited state that can undergo efficient reductive quenching processes to facilitate organic reactions. In particular, UNLPF-12 exhibits both outstanding photostability and efficient photocatalytic activities toward a range of important organic transformations including aerobic hydroxylation of arylboronic acids, amine coupling, and the Mannich reaction

Porphyrin-Metalation-Mediated Tuning of Photoredox Catalytic Properties in Metal–Organic Frameworks

Photoredox catalytic activation of organic molecules via single-electron transfer processes has proven to be a mild and efficient synthetic methodology. However, the heavy reliance on expensive ruthenium and iridium complexes limits their applications for scale-up synthesis. To this end, photoactive metal–organic frameworks (MOFs) exhibit unique advantages as novel heterogeneous photocatalytic systems, yet their utilization toward organic transformations has been limited. Here we describe the preparation and synthetic applications of four isostructural porphyrinic MOFs, namely, UNLPF-10a, -10b, -11, and -12, which are composed of free base, In^III-, Sn^IVCl₂-, and Sn^IV-porphyrin building blocks, respectively. We demonstrate that the metalation with high valent metal cations (In^III and Sn^IV) significantly modifies the electronic structure of porphyrin macrocycle and provides a highly oxidative photoexcited state that can undergo efficient reductive quenching processes to facilitate organic reactions. In particular, UNLPF-12 exhibits both outstanding photostability and efficient photocatalytic activities toward a range of important organic transformations including aerobic hydroxylation of arylboronic acids, amine coupling, and the Mannich reaction