Paramagnetic Cobalt(II) Complexes with Cyclam Derivatives: Toward 19F MRI Contrast Agents.
Jan BlahutLadislav BendaJan KotekGuido PintacudaPetr HermannPublished in: Inorganic chemistry (2020)
In order to develop novel, more efficient, and/or selective contrast agents for magnetic resonance imaging (MRI), different modi operandi are explored as alternatives to water-relaxation enhancement. In this work, cobalt(II/III) complexes of bis(N-trifluoroethyl)cyclam derivatives with two acetate or two phosphonate pendant arms, H2te2f2a and H4te2f2p, were prepared and investigated. X-ray diffraction structures confirmed octahedral coordination with a very stable trans-III cyclam conformation and with fluorine atoms located about 5.3 Å from the metal center. The Co(II) complexes are kinetically inert, decomposing slowly even in 1 M aqueous HCl at 80 °C. The Co(II) complexes exhibited well-resolved paramagnetically shifted NMR spectra. These were interpreted with the help of quantum chemistry calculations. The 13C NMR shifts of the trans-[CoII(te2f2p)]2- complex were successfully assigned based on spin density delocalization within the ligand molecule. The obtained spin density also helps to describe d-metal-induced NMR relaxation properties of 19F nuclei, including the contribution of a Fermi contact relaxation mechanism. The paramagnetic complexes show convenient relaxation properties to be used as 19F MRI contrast agents.
Keyphrases
- contrast enhanced
- magnetic resonance
- magnetic resonance imaging
- high resolution
- single molecule
- density functional theory
- diffusion weighted imaging
- computed tomography
- solid state
- molecular dynamics
- room temperature
- dual energy
- atomic force microscopy
- mass spectrometry
- oxidative stress
- drug induced
- quantum dots
- crystal structure
- diabetic rats