A hexaaza macrocyclic ligand containing acetohydrazide pendants for Ln(III) complexation in aqueous solution....

Area of Science:

• Coordination Chemistry
• Inorganic Chemistry
• Lanthanide Chemistry

Background:

• Hexaaza macrocyclic ligands offer unique coordination environments for metal ions.
• Lanthanide complexes are of interest due to their diverse applications in catalysis, imaging, and materials science.

Purpose of the Study:

• To synthesize and characterize novel lanthanide complexes with a hexaaza macrocyclic ligand bearing acetohydrazide pendants.
• To investigate the structural properties of these complexes in both solid-state and aqueous solution.

Main Methods:

• Single-crystal X-ray crystallography for solid-state structure determination.
• Density-functional theory (DFT) calculations (B3LYP model) for theoretical structural analysis.
• Paramagnetic Nuclear Magnetic Resonance (NMR) spectroscopy for solution structure elucidation.

Main Results:

• The crystal structure of the ligand and its lanthanum complex ([La(L)](3+)) revealed a ten-coordinate metal ion with alternating acetohydrazide pendant positions.
• The ethylenediamine moieties in the ligand adopt (deltadelta) or (lambdalambda) conformations.
• DFT calculations and NMR measurements confirmed good agreement between theoretical and experimental structures, indicating a D(2) symmetry in solution.

Conclusions:

• Lanthanide complexes with the studied hexaaza macrocyclic ligand can be successfully synthesized and structurally characterized for lighter lanthanides.
• The acetohydrazide pendants play a crucial role in the coordination and structural ổn định of the complexes.
• The combination of experimental and computational methods provides a comprehensive understanding of the structural behavior of these lanthanide complexes in different environments.