Towards Ni(II) complexes with spin switches for ¹⁹F MR-based pH sensing.

Area of Science:

• Coordination Chemistry
• Magnetic Resonance Imaging
• Fluorine Chemistry

Background:

• Fluorinated nickel complexes offer tunable properties for sensing applications.
• Spin state and coordination geometry changes can be exploited for signal transduction.
• ¹⁹F MRI provides high sensitivity and specificity for fluorine-containing agents.

Purpose of the Study:

• To investigate fluorinated Ni(II) complexes for ¹⁹F MRI-based pH sensing.
• To evaluate the potential of simultaneous changes in coordination geometry and spin state.
• To establish a framework for developing novel pH mapping agents.

Main Methods:

• Synthesis and characterization of Ni(II) complexes (NiL₁, NiL₂).
• Determination of crystal structures and solution magnetic moments.
• ¹⁹F MRI acquisition on a 7.0-T scanner using a quadrature ¹⁹F volume coil.

Main Results:

• NiL₁ was diamagnetic; NiL₂ was paramagnetic.
• Both complexes exhibited ligand dissociation around pH 6, limiting reversible pH sensing.
• Distinct ¹⁹F NMR signals allowed selective imaging of NiL₁ and NiL₂ via ¹⁹F MRI.

Conclusions:

• Selective ¹⁹F MRI imaging of NiL₁ and NiL₂ was achieved due to differences in chemical shift and relaxation times.
• The complexes' instability in acidic conditions necessitates further ligand scaffold development.
• This study provides a foundation for creating advanced agents for ratiometric pH mapping using ¹⁹F MRI.