Variable denticity in carboxylate binding to the uranyl coordination complexes.

Area of Science:

• Inorganic Chemistry
• Coordination Chemistry
• Spectroscopy

Background:

• Uranyl complexes are important in nuclear chemistry and materials science.
• Understanding the coordination environment of uranyl ions is crucial for predicting their reactivity and properties.
• Mass spectrometry and infrared spectroscopy are powerful tools for characterizing metal complexes.

Purpose of the Study:

• To synthesize and characterize tris-carboxylate complexes of uranyl with acetate and benzoate ligands.
• To determine the binding modes of acetate and benzoate ligands to the uranyl ion using vibrational spectroscopy.
• To elucidate the predominant conformers of these uranyl complexes.

Main Methods:

• Generation of uranyl carboxylate complexes using electrospray ionization mass spectrometry (ESI-MS).
• Isolation and characterization of anionic complexes in a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR-MS).
• Wavelength-selective infrared multiple photon dissociation (IRMPD) spectroscopy.
• Density functional theory (DFT) calculations for spectral interpretation.

Main Results:

• Successful generation and isolation of tris-acetato and tris-benzoato uranyl anions.
• IRMPD of tris-acetato uranyl anion yielded a spectrum interpretable by DFT, indicating two bidentate and one monodentate acetate ligand.
• IRMPD of tris-benzoato uranyl anion yielded a spectrum consistent with one monodentate and two bidentate benzoate ligands.

Conclusions:

• The predominant conformer of the tris-acetato uranyl complex features two bidentate and one monodentate acetate ligand.
• The tris-benzoato uranyl complex predominantly adopts a structure with one monodentate and two bidentate benzoate ligands.
• Vibrational spectroscopy combined with DFT calculations provides detailed structural insights into uranyl carboxylate complexes.