Lanthanide Complexes as Paramagnetic Probes for ¹⁹F Magnetic Resonance

The physicochemical basis of probe design for 19 F MRS and MRI applications is reviewed. Complexes that give a single major resonance in solution are described, in which the Ln 3+ ion is about 6 Å from the 19 F label. Sensitivity improvements of 15‐fold are reported in both imaging and spectroscopy based on longitudinal relaxation enhancement. The pseudocontact shift allows an amplification of chemical shift non‐equivalence in responsive 19 F probes, e.g. for monitoring pH in the range between 5 and 8.