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Preparation, Purification, and Characterization of Lanthanide Complexes for Use as Contrast Agents for Magnetic Resonance Imaging
Published on: July 21, 2011
Exploring Covalency in f-Element Complexes: Dithiocarbamate Ligands Reveal Differences Between Heavy Actinides and
William Quintero-Martinez1,2, Dayán Páez-Hernández2,3
1Doctorado en Fisicoquímica Molecular, Universidad Andres Bello, República 275, Santiago 8370146, Chile.
Covalence in actinides and lanthanides differs significantly. Heavy actinides exhibit greater covalence, especially in higher oxidation states, driven by energy degeneracy rather than orbital overlap, with sulfur ligands enhancing this effect.
Area of Science:
- Inorganic Chemistry
- Quantum Chemistry
- Theoretical Chemistry
Background:
- Covalence is key to understanding actinide and lanthanide properties.
- Differences in electronic structure lead to distinct chemical behaviors.
- Dithiocarbamate ligands offer a unique system for studying f-element bonding.
Purpose of the Study:
- To systematically analyze covalence in actinide and lanthanide complexes.
- To compare the bonding characteristics of actinides versus lanthanides.
- To elucidate the factors driving covalence in f-elements.
Main Methods:
- Analysis of trivalent and tetravalent actinide (U-Fm) and lanthanide (Nd-Er) complexes.
- Application of Slater-Condon parameters.
- Utilizing Quantum Theory of Atoms in Molecules (QTAIM) with bond critical points (BCP) and natural localized molecular orbitals (NLMOs).
- Inclusion of multiconfigurational effects, scalar relativistic effects, and spin-orbit coupling.
Main Results:
- Significant differences in covalence were observed between heavy actinides and lanthanides.
- Higher covalence correlates with higher oxidation states in metal ions.
- QTAIM analysis indicates energy-degeneracy driven covalence in heavy actinides, not orbital overlap.
- Sulfur donor atoms promote covalence in heavy actinides more than oxygen.
Conclusions:
- Heavy actinides display distinct covalent properties compared to lanthanides.
- Covalence in heavy actinides is influenced by electronic degeneracies and softer donor atoms like sulfur.
- These findings establish actinides as softer Lewis acids than their lanthanide counterparts.
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