Dipyrrinato-Iridium(III) Complexes for Application in Photodynamic Therapy and Antimicrobial Photodynamic Inactivation.


Hohlfeld BF(1)(2), Gitter B(2), Kingsbury CJ(3), Flanagan KJ(3), Steen D(2), Wieland GD(2), Kulak N(1)(4), Senge MO(3)(5), Wiehe A(1)(2).
Author information:
(1)Institut für Chemie u. Biochemie, Freie Universität Berlin, Takustr. 3, 14195, Berlin, Germany.
(2)biolitec research GmbH, Otto-Schott-Str. 15, 07745, Jena, Germany.
(3)Medicinal Chemistry, Trinity Translational Medicine Institute, Trinity Centre for Health Sciences, Trinity College Dublin, The University of Dublin, St James's Hospital, Dublin, 8, Ireland.
(4)Institut für Chemie, Otto-von-Guericke-Universität Magdeburg, Universitätsplatz 2, 39106, Magdeburg, Germany.
(5)Institute for Advanced Study
(TUM-IAS), Technical University of Munich, Lichtenbergstrasse 2a, 85748, Garching, Germany.


The generation of bio-targetable photosensitizers is of utmost importance to the emerging field of photodynamic therapy and antimicrobial (photo-)therapy. A synthetic strategy is presented in which chelating dipyrrin moieties are used to enhance the known photoactivity of iridium(III) metal complexes. Formed complexes can thus be functionalized in a facile manner with a range of targeting groups at their chemically active reaction sites. Dipyrrins with N- and O-substituents afforded (dipy)iridium(III) complexes via complexation with the respective Cp*-iridium(III) and ppy-iridium(III) precursors (dipy=dipyrrinato, Cp*=pentamethyl-η5 -cyclopentadienyl, ppy=2-phenylpyridyl). Similarly, electron-deficient [IrIII (dipy)(ppy)2 ] complexes could be used for post-functionalization, forming alkenyl, alkynyl and glyco-appended iridium(III) complexes. The phototoxic activity of these complexes has been assessed in cellular and bacterial assays with and without light; the [IrIII (Cl)(Cp*)(dipy)] complexes and the glyco-substituted iridium(III) complexes showing particular promise as photomedicine candidates. Representative crystal structures of the complexes are also presented.