Equatorial Ligation Controls 5f Electron Binding in Penta- and Hexavalent Uranyl Acetate Complexes.

Area of Science:

• Inorganic Chemistry
• Physical Chemistry
• Computational Chemistry

Background:

• Uranyl complexes are crucial in nuclear energy and environmental science.
• Understanding their electronic structure is vital for predicting chemical behavior and stability.
• Acetate ligands play a significant role in the coordination chemistry of uranyl ions.

Purpose of the Study:

• To investigate the electronic structures of diacetate and triacetate uranyl complex anions.
• To determine the role of coordination number in the electronic properties and stability of these anions.
• To elucidate the nature of the detached electron and bonding characteristics in these complexes.

Main Methods:

• Anion photoelectron spectroscopy (aPES) was used to probe electronic structures.
• Relativistic electronic-structure calculations were employed to interpret experimental data.
• Electrospray and photodetachment techniques were utilized for anion generation and analysis.

Main Results:

• Vertical electron detachment energies were experimentally determined as 2.77 eV for (AcO)2UO2- and 6.02 eV for (AcO)3UO2-.
• Electronic structure calculations confirmed a U(V)(5f1) center in (AcO)2UO2- and a U(VI)(5f0) center in (AcO)3UO2-.
• The detached electron in (AcO)2UO2- originates from the 5f orbital, exhibiting spin-orbit effects, while in (AcO)3UO2-, it comes from an acetate oxygen.

Conclusions:

• Higher coordination numbers in uranyl acetate complexes modulate 5f electron participation in bonding.
• Increased coordination enhances the stabilization of the anionic complexes.
• U-O bonds in these complexes are predominantly ionic with limited covalent character.