Non-covalent interactions of uranyl complexes: a theoretical study.

Area of Science:

• Inorganic Chemistry
• Computational Chemistry
• Materials Science

Background:

• Uranyl complexes are crucial in nuclear chemistry and materials science.
• Understanding their intermolecular interactions, like hydrogen and halogen bonding, is key to predicting their behavior.
• Previous studies have not fully elucidated the hydrogen bonding capabilities of the uranyl moiety.

Purpose of the Study:

• To theoretically investigate the hydrogen and halogen bonding potential of model uranyl complexes.
• To determine the role of uranyl and its coordinated water molecules in these interactions.
• To analyze the electronic structure origins of observed bonding behaviors.

Main Methods:

• Theoretical calculations including potential energy scans and geometry optimization.
• Utilizing various computational methods: Density Functional Theory (DFT), coupled-cluster, MP2, and double-hybrid DFT.
• Analysis of interaction energies, vibrational frequencies, and electronic structure using Atoms-in-Molecules and Natural Bond Orbital theory.
• Validation against experimental data from the Cambridge Structural Database.

Main Results:

• Uranyl (UO2) is confirmed as a weak hydrogen bond acceptor.
• Equatorially coordinated water molecules act as strong hydrogen bond donors.
• Calculated interaction energies showed minimal dependence on the chosen theoretical method.
• A cyclic structure was optimized for a 1:1 uranyl:water complex.
• Electronic structure analysis revealed covalency in U-Oyl bonds due to U 5f and 6d orbital contributions.

Conclusions:

• Model uranyl complexes exhibit distinct hydrogen bonding roles: weak acceptance by uranyl and strong donation by coordinated water.
• Computational methods provide reliable predictions for these interactions.
• The electronic structure, specifically the covalency of U-Oyl bonds, dictates uranyl's weak acceptor capability.