Relativistic DFT Probe for Reaction Energies and Electronic/Bonding Properties of Polypyrrolic Hetero-Bimetallic Actinide Complexes: Effects of Uranylendo-Oxo Functionalization

Abstract

A series of hetero-bimetallic actinide complexes of the Schiff-base polypyrrolic macrocycle (L), featuring cation− cation interactions (CCIs), were systematically investigated using relativistic density functional theory (DFT). The tetrahydrofuran (THF) solvated complex [(THF)(OU VI OU IV )(THF)(L)] 2+ has high reaction free energy (Δ r G), and its replacement with electrondonating iodine promotes the reaction thermodynamics to obtain uranyl iodide [(I)(OU VI OU IV )(I)(L)] 2+ (U VI −U IV ). Retaining this coordination geometry, calculations have been extended to other An(IV) (An = Th, Pa, Np, Pu), i.e., for the substitution of U(IV) to obtain U VI −An IV . As a consequence, the reaction free energy is appreciably lowered, suggesting the thermodynamic feasibility for the experimental synthesis of these bimetallic complexes. Among all U VI −An IV , the electron-spin density and high-lying occupied orbitals of U VI −Pa IV show a large extent of electron transfer from electron-rich Pa(IV) to electron-deficient U(VI), leading to a more stable U V −Pa V oxidation state. Additionally, the shortest bond distance and the comparatively negative E int of the Pa−O endo bond suggest more positive and negative charges (Q) of Pa and endooxo atoms, respectively. As a result of the enhanced Pa−O endo bond and strong CCI in U VI −Pa IV along with the corresponding lowest reaction free energy among all of the optimized complexes, uranyl species is a better candidate for the experimental synthesis in the ultimate context of environmental remediation.

Theoretical Investigation of Catalytic Water Splitting by the Arene-Anchored Actinide Complexes

“…At the Priroda-optimized geometries, electronic structures were calculated in a tetrahydrofuran (THF) solution by using the ADF 2014 program . This approximation has proven to be reliable as re-optimizations have only a very slight effect on the structural parameters and molecular properties. − The default convergence criterion of 10 –6 au was used, and an integration parameter of 6.0 was applied. The solvation was taken into account using the Conductor-Like Screening Model, COSMO. , A dielectric constant of 7.58 was applied for THF, associated with the E surf -type of cavity.…”

“…The Klamt radii were used for the main group atoms ( H = 1.30 Å, C = 2.00 Å, and O = 1.72 Å). Also, ones for actinide in different oxidation states V/IV/III were Pa of 1.69/1.72/1.87 Å, U of 1.70/1.70 Å/1.85, and Np of 1.55/1.71/1.86. ,, We used both scalar and spin–orbit coupling (SOC) relativistic ZORA methods of van Lenthe, along with the PBE functional and Slater-type TZP basis sets. , Under the small-core ZORA, the core orbitals 1s–4f were frozen for Pa, U, and Np and ones of 1s for C and O.…”

CO2 Cleavage Reaction Driven by Alkylidyne Complexes of Group 6 Metals and Uranium: A Density Functional Theory Study on Energetics, Reaction Mechanism, and Structural/Bonding Properties

“…All geometrical optimizations were carried out using the ADF program (2014 edition). − The scalar relativistic ZORA Hamiltonian, the Slater-type TZP basis sets, and the PBE functional were used. The GGA-PBE functional has been proved to be not only accurate and reliable in calculations of transition metal and actinide complexes but also highly efficient to study large molecular complexes. ,− According to small-core ZORA basis sets, the core orbitals were frozen, including 1s-2p, 1s-3d, 1s-4d, and 1s-4f for Cr, Mo, W, and U, respectively, and 1s for C, N, O and F. The criterion of SCF convergence is 10 –6 a.u., and the integral lattice parameters are 6.0*6.0*6.0. At each optimized geometry, frequency calculation was conducted to confirm whether the structure is a stable state or transition state (TS).…”

Multireference Wavefunction-Based Investigation of the Ground and Excited States of LrF and LrO

“…Due to their greater efficiency in comparison to ab initio electronic correlation methods, density functional theory (DFT)-based approaches are often selected for heavy element species. − ,− However, they are typically less accurate than ab initio correlated methods. Despite this, it is still important to consider the performance of DFT approaches in the prediction of chemical properties.…”