Universität zu Köln

Sadhu, Biswajit and Dolg, Michael ORCID: 0000-0002-0538-0837 (2019). Enhancing Actinide(III) over Lanthanide(III) Selectivity through Hard-by-Soft Donor Substitution: Exploitation and Implication of Near-Degeneracy-Driven Covalency. Inorg. Chem., 58 (15). S. 9738 - 9749. WASHINGTON: AMER CHEMICAL SOC. ISSN 1520-510X

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Abstract

Soft donor ligands often provide higher selectivity for actinides(III) over chemically similar lanthanides(III), e.g., in the Am-III-Eu-III pair. Frequently, the origin of such selectivity is associated with an increased covalency in actinide-ligand bonding. However, the relationship between the degree of covalency and ion selectivity has yet to reach general consensus. Further, it is unclear whether the enhanced covalency leads to a thermodynamic stabilization of the complex or not. Using relativistic density functional theory, we have addressed these outstanding issues by analyzing the subtle change of metal-ligand interactions from a hard donor ligand to a mixed soft-hard one. The present comparative study on the structure of and binding in Am3+ and Eu3+ complexes with 3,4,3-LI(1,2-HOPO) (L) and its mixed-donor variant (LS) shows that the introduction of sulfur as a soft donor atom into the metal coordination sphere indeed infuses an Am3+ selectivity into the otherwise nonselective ligand L but also leads to a significant reduction of the metal-binding Gibbs free energies. Natural population analysis, charge decomposition analysis, and its extended version point to the critical role of ligand-to-metal charge transfer in the overall thermodynamic stability of the complexes. A detailed energy decomposition analysis combining the extended transition state with the natural orbitals chemical valence method reveals an enhancement of the covalency upon switching to the soft-hard donor ligand because of the different nature of the metal-ligand interaction. The ligand L predominantly binds the metal via pi donation, whereas the ligand LS prefers sigma donation. Molecular orbital and quantum theory of atoms in molecules analyses as well as a comparison to a simple model system show that the covalency occurs as a result of orbital mixing and is near-degeneracy-driven in nature. This enhanced covalency, however, fails to thermodynamically compensate for the loss of strong electrostatic interaction and thus does not lead to an additional stabilization of the metal-LS complexes.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Sadhu, Biswajit UNSPECIFIED UNSPECIFIED UNSPECIFIED Dolg, Michael UNSPECIFIED orcid.org/0000-0002-0538-0837 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-144772
DOI:	10.1021/acs.inorgchem.9b00705
Journal or Publication Title:	Inorg. Chem.
Volume:	58
Number:	15
Page Range:	S. 9738 - 9749
Date:	2019
Publisher:	AMER CHEMICAL SOC
Place of Publication:	WASHINGTON
ISSN:	1520-510X
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Chemistry > Institute of Theoretical Chemistry
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language CHARGE DECOMPOSITION ANALYSIS; ZETA VALENCE QUALITY; BASIS-SETS; EFFICIENT SEPARATION; NATURAL-POPULATION; CORRELATION-ENERGY; HARTREE-FOCK; M06 SUITE; EU-III; DENSITY Multiple languages Chemistry, Inorganic & Nuclear Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/14477