Trifluoroborate-appended cyclen complexes of paramagnetic transition metals (Ni2+, Co2+) as fast-relaxing 19F MRI probes.  

C. Sire, F. Garello, N. Lalaoui, N. Saffon-Merceron, N. Le Poul, R. Tripier, L. Tei, T. Troadec, Dalton Transactions 2025, DOI: 10.1039/D5DT01834J.

For the first time, trifluoroborate groups (BF₃s) have been investigated as sensitive probes for ¹⁹F Magnetic Resonance Imaging (MRI) in paramagnetic complexes. Using a macrocyclic BF₃-appended cyclen ligand, complexes of Ni²⁺ and Co²⁺ cations were synthesized and exhibited very fast T₁ and T₂ relaxation times that improve ¹⁹F MRI detection. Notably, the cobalt complex presents the fastest ¹⁹F MRI relaxation reported to date for a Co²⁺-based probe.