Complexation of Lanthanides with Glutaroimide-dioxime: Binding Strength and Coordination Modes

Area of Science:

• Coordination Chemistry
• Lanthanide Chemistry
• Supramolecular Chemistry

Background:

• Glutaroimide-dioxime (H2L) is a cyclic ligand known to form stable complexes with actinides and transition metals.
• Lanthanide complexation with H2L has not been extensively studied.
• Understanding lanthanide-ligand interactions is crucial for various applications.

Purpose of the Study:

• To investigate the complexation behavior of lanthanides (Nd(3+), Eu(3+)) with glutaroimide-dioxime (H2L).
• To determine the stoichiometry, stability, and thermodynamic properties of these lanthanide complexes.
• To elucidate the coordination mode and structural features of the complexes.

Main Methods:

• Potentiometry
• Absorption spectrophotometry
• Luminescence spectroscopy
• Microcalorimetry
• Single-crystal X-ray diffractometry

Main Results:

• Lanthanides form three successive complexes with H2L: M(HL)(2+), M(HL)L, and M(HL)2(+).
• Complexation is exothermic, indicating favorable interactions.
• Stability constants are lower than Fe(3+) complexes but comparable to UO2(2+) complexes.
• X-ray crystallography reveals tridentate coordination of H2L to Eu(3+) via oxime oxygen and imide nitrogen atoms.

Conclusions:

• Glutaroimide-dioxime (H2L) effectively coordinates lanthanides through a tridentate mode, forming stable complexes.
• Proton relocation and deprotonation of H2L create a conjugated system enhancing complex stability.
• The study provides insights into lanthanide-ligand interactions and the potential of H2L in coordination chemistry.