Exploring the Interaction Natures in Plutonyl (VI) Complexes with Topological Analyses of Electron Density.

Jiguang Du,Gang Jiang,Xiyuan Sun

doi:10.3390/ijms17040414

Abstract

The interaction natures between Pu and different ligands in several plutonyl (VI) complexes are investigated by performing topological analyses of electron density. The geometrical structures in both gaseous and aqueous phases are obtained with B3LYP functional, and are generally in agreement with available theoretical and experimental results when combined with all-electron segmented all-electron relativistic contracted (SARC) basis set. The Pu– bond orders show significant linear dependence on bond length and the charge of oxygen atoms in plutonyl moiety. The closed-shell interactions were identified for Pu-Ligand bonds in most complexes with quantum theory of atoms in molecules (QTAIM) analyses. Meanwhile, we found that some Pu–Ligand bonds, like Pu–OH−, show weak covalent. The interactive nature of Pu–ligand bonds were revealed based on the interaction quantum atom (IQA) energy decomposition approach, and our results indicate that all Pu–Ligand interactions is dominated by the electrostatic attraction interaction as expected. Meanwhile it is also important to note that the quantum mechanical exchange-correlation contributions can not be ignored. By means of the non-covalent interaction (NCI) approach it has been found that some weak and repulsion interactions existed in plutonyl(VI) complexes, which can not be distinguished by QTAIM, can be successfully identified.

Highlights

Plutonium is the only element in the periodic table that can have appreciable amounts of four different oxidation states existing in aqueous acidic solutions simultaneously
We first optimized the structures of bare plutonyl moieties (PuO22/1+) and pentaaquo complexes to test the reliability of DFT functionals and basis set employed in our present work
Our results indicate that that the PuO2(CO3)(H2O)3 q (Pu)–Oxygen in plutonyl (Oyl) bond lengths calculated with B3LYP/segmented all-electron relativistic contracted (SARC)-zero-order regular approximation (ZORA) are closer to experimental values [1,32] relative to the B3LYP/SDD results

Summary

Introduction

Plutonium is the only element in the periodic table that can have appreciable amounts of four different oxidation states existing in aqueous acidic solutions simultaneously. Tremendous theoretical works with quantum mechanical methods have been performed to probe the structural and electronic properties and spectra of plutonyl complexes. The chemical bonding natures of Uranyl (VI) complexes have been recently identified by Vallet et al [13] with electron density topological analyses methods, namely the quantum theory of atoms in molecules (QTAIM) proposed by Bader [14]. Based on the gaseous electron density, the QTAIM and interaction quantum atom (IQA) [16] analyses were performed to identify the interaction nature between Pu and coordinating ligands Another density-based analytical tool, the electron localization function (ELF) [17], was utilized to study the chemical bondings. As an excellent extension of QTAIM theory, the non-covalent interaction (NCI) index proposed by Yang et al [18] was used to probe into the weak interactions in the complexes studied

Computational Details

Structures in Gaseous and Solution Phases

Natural Bonding Orbital Analyses

QTAIM Topological Analyses

Conclusions

Correction note