Accessibility of Uranyl-Plutonium Complex Supported by a Polypyrrolic Macrocycle: An Implication for Experimental...

Area of Science:

• Inorganic Chemistry
• Computational Chemistry
• Actinide Chemistry

Background:

• Uranyl complexes with An^IIICp₃ (An = Np, U) form cation-cation interaction (CCI) complexes.
• Synthesis of analogous uranyl-plutonium complexes has been challenging.
• Polypyrrolic macrocycles and cyclopentadienyl ligands are key components in these systems.

Purpose of the Study:

• To computationally investigate the formation reactions of uranyl-An complexes.
• To explore strategies for synthesizing uranyl-plutonium complexes.
• To understand the electronic structure and bonding in these heavy element systems.

Main Methods:

• Scalar relativistic density functional theory (DFT) calculations were employed.
• Investigated formation reactions of (THF)(A₂L)(OUO)-An(CpX)₃ systems (A=Li, H; An=Pu, Np, U; X=Me, H, Cl, SiMe₃).
• Analyzed electronic structures, electron transfer, and bonding properties.

Main Results:

• Utilizing a lithiated uranyl precursor, (THF)(Li₂L)(U^VIO₂), facilitated the formation of a uranyl-plutonium complex.
• The reaction free energy for uranyl-Pu complex formation became exergonic, indicating thermodynamic feasibility.
• Calculations revealed a U^V-Pu^IV oxidation state and significant electron transfer, strengthening the cation-cation interaction.

Conclusions:

• A lithiated precursor strategy enhances uranyl precursor reactivity, enabling the synthesis of previously inaccessible uranyl-plutonium complexes.
• This approach also improves the formation energetics for uranyl-Np and uranyl-U analogues.
• Modifying cyclopentadienyl ligands to increase plutonium reactant reactivity was less effective.