Gd(III) and Yb(III) Complexes Derived from a New Water-Soluble Dioxopolyazacyclohexane Macrocycle

Area of Science:

• Coordination Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Macrocyclic ligands are crucial in coordination chemistry, influencing metal ion complex properties.
• Diethylenetriaminepentaacetic (DTPA) derivatives are widely used chelators.
• Understanding metal complex structures is key to developing new functional materials.

Purpose of the Study:

• Synthesize a novel macrocyclic ligand using DTPA dianhydride and trans-1,4-diaminocyclohexane.
• Prepare and characterize Gadolinium(III) and Ytterbium(III) complexes of the new ligand.
• Investigate the structural and relaxivity properties of the Gd(III) complex.

Main Methods:

• Ligand synthesis via condensation reaction.
• Characterization using spectroscopic methods (e.g., NMR, IR).
• Density Functional Theory (DFT) for structural and electronic calculations.
• Longitudinal relaxation time (T1) measurements for relaxivity determination.

Main Results:

• Successful synthesis and characterization of the macrocyclic ligand and its Gd(III)/Yb(III) complexes.
• DFT calculations revealed minimized conformational strain and elucidated coordination modes.
• Gd(III) complex exhibited favorable T1 relaxivity due to a specific structural feature facilitating water exchange.

Conclusions:

• The novel macrocyclic ligand forms stable Gd(III) and Yb(III) complexes.
• The ligand's conformation, dictated by amide groups and the cyclohexane ring, is critical for metal coordination and relaxivity.
• The Gd(III) complex shows promise for applications requiring efficient water relaxation, such as MRI contrast agents.