Highly fluorinated metal complexes as dual ¹⁹F and PARACEST imaging agents

We reported a set of water-soluble transition metal complexes that can serve as both ¹⁹F and PARACEST magnetic resonance imaging agents. The high number of equivalent fluorine atoms and the paramagnetic effect of metals offer these complexes high ¹⁹F sensitivity as demonstrated by in vitro¹⁹F MRI experiments. The complexes contain carboxamide groups appended onto a cyclen macrocycle, which provide ¹H CEST peaks well differentiated from bulk water. The Co(ii) agent displays two CEST peaks that can be utilized for ratiometric pH determination and the concept of combining ¹⁹F MR and PARACEST as complementary imaging techniques was demonstrated with the Fe(ii) complex.