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 vitro 19F 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.