Quantum chemical study of reaction mechanism between plutonium and nitrogen

The study of the reaction between plutonium and nitrogen is helpful in further understanding the interaction between plutonium and air molecules. Currently, there is no research on the microscopic reaction mechanism of plutonium nitridation reactions. Therefore, the microscopic mechanism of the Pu with N₂ gas phase reaction is explored in this study, based on density functional theory (DFT) using different basis functions. In this paper, the geometry of stationary points on the potential energy surface is optimized. In addition, the transition states are verified by frequency analysis and intrinsic reaction coordination (IRC). Finally, we obtained the reaction potential energy curve and micro reaction pathways. Analysis of the reaction mechanism shows that the reaction of Pu with N₂ has two pathways. Pathway 1 (Pu + N₂ → R1 → TS1 → PuN₂) has a T-shaped transition state and pathway 2 (Pu + N₂ → R2 → TS2 → PuN + N) has an L-shaped transition state. Both transition states have only one imaginary frequency. According to the comparison of the energy at each stagnation point along the two pathways, and the heat energy emitted by the two reaction paths, we found that pathway 1 is the main reaction pathway. The nature of Pu-N bonding evolution along the pathways was studied by atoms in molecules (AIM) and electron localization function (ELF) topological approaches. In order to analyze the role of the plutonium atom 5f orbital in the reaction, the variation in density state along the pathways was measured. Results show that the 5f orbital mainly contributes to the formation of Pu-N bonds, and the influence of temperature on the reaction rate is revealed by calculating the rate constants of the two reaction pathways.

HMNTA Complexes of Tetravalent Metal Ions: On the Roles of Carbonyl Oxygen and Amine Nitrogen in the Stabilization of Gas-Phase M(HMNTA)24+ Complexes

Gas-phase tetrapositively charged M(HMNTA)₂⁴⁺ (M = Zr, Hf, Th, and U) ions were generated via electrospray ionization of the M(ClO₄)₄ and N,N,N',N',N″,N″-hexamethylnitrilotriacetamide (HMNTA) mixtures in acetonitrile. In these complexes, the Zr⁴⁺, Hf⁴⁺, Th⁴⁺, and U⁴⁺ metal centers are coordinated by two neutral HMNTA ligands forming antitriangular prism geometry on the basis of DFT calculations. Bonding analysis reveals that the M⁴⁺ center is stabilized by six carbonyl oxygen atoms, while the interactions between M⁴⁺ and two central amine nitrogen atoms are negligible. This is further confirmed by the calculation results of two tetrapositive model complexes without either central amine nitrogen or carbonyl oxygen atoms, indicating the central nitrogen atom of HMNTA is not necessary in forming tetrapositive metal complexes that can be stabilized in gas phase. Collision-induced dissociation of Zr(HMNTA)₂⁴⁺, Hf(HMNTA)₂⁴⁺, and Th(HMNTA)₂⁴⁺ shows the formation of similar charge reducing products with the oxidation state of metal retaining IV whereas ions with other oxidation states were observed for the fragmentation products of U(HMNTA)₂⁴⁺.

Relativistic Effects Stabilize the Planar Wheel-like Structure of Actinide-Doped Gold Clusters: An@Au7 (An = Th to Cm)

Despite the chemistry of actinide-ligand bonding is continuing and of burgeoning interest, investigations of the chemical bonding of bimetallic complexes involving transuranics remain relatively less, and there are rarely studies on the bonding features between actinide and coinage metals (CM). We present a systematic research on the series of An@Au₇ (An = Th to Cm), UCM₇ (CM = Cu, Ag, Au), and WAu₇ clusters to investigate the unique geometries, electronic structures, and chemical bonding between An 5f6d orbitals and CM ns orbitals, and to find their periodicity across the actinides and within the group of transition metals. A unique planar wheel-like structure for An@Au₇ clusters with the help of actinide metals encapsulation via spin-orbit coupling, resulting in An(III). Instead, the transition-metal (TM) element W retains its usual six-gold-coordination structure in WAu₇, thus forcing the seventh Au out of plane. The An-CM interactions, depending on the ion radii, become stronger with the increase of the atomic number of the actinide metals, as well as the CM. These results show that the presence of actinides in clusters can lead to unique electronic and geometrical structures.

Electronic Structure and Chemical Bonding of [AmO2(H2O) n ]2+/1

Systematic americyl-hydration cations were investigated theoretically to understand the electronic structures and bonding in [(AmO2)(H2O) n ]2+/1+ (n = 1-6). We obtained the binding energy using density functional theory methods with scalar relativistic and spin-orbit coupling effects. The geometric structures of these species have been investigated in aqueous solution via an implicit solvation model. Computational results reveal that the complexes of five equatorial water molecules coordinated to americyl ions are the most stable due to the enhanced ionic interactions between the AmO2 2+/1+ cation and multiple oxygen atoms as electron donors. As expected, Am-Owater bonds in such series are electrostatic in nature and contain a generally decreasing covalent character when hydration number increases.

Can water continuously oxidize the PuO molecule? Mechanisms, topological analysis and rate constant calculations

A detailed description of the PuO continuously oxidized by water in the gas-phase.