Redox Potentials of Uranyl Ions in Macrocyclic Complexes: Quantifying the Role of Counter-Ions

Abstract

Several uranyl ions strapped with Schiff-base ligands in the presence of redoxinnocent metal ions are synthesized, and their reduction potentials are recently estimated. The change in Lewis acidity of the redox-innocent metal ions contributes to ∼60 mV/pK a unit quantified which is intriguing. Upon increasing the Lewis acidity of metal ions, the number of triflate molecules found near the metal ions also increases whose contributions toward the redox potentials remain poorly understood and not quantified until now. Most importantly, to ease the computational burden, triflate anions are often neglected in quantum chemical models due to their larger size and weak coordination to metal ions. Herein, we have quantified and dissected the individual contributions that arise alone from Lewis acid metal ions and from triflate anions with electronic structure calculations. The triflate anion contributions are large, in particular, for divalent and trivalent anions that cannot be neglected. It was presumed to be innocent, but we here show that they can contribute more than 50% to the predicted redox potentials, suggesting that their vital role in the overall reduction processes cannot be neglected.

Structural distortion by alkali metal cations modulates the redox and electronic properties of Ce3+ imidophosphorane complexes

“…The correlation between the shift in E pa and electrostatic/Lewis acidic properties of the redox-inactive metal cation is well established in the literature across multiple classes of transition metal and uranyl complexes. 29–38,49–51 The data presented herein demonstrate the impact of structural distortion by alkali metal bound in the secondary coordination sphere on the Ce 3+ oxidation potential within an imidophosphorane framework. Quantification of the distortion of the ligand sphere by means of Σ Δ109.5 elucidates a linear, positive relationship between structural distortion and oxidation potential.…”

Thorium Complexation with Aliphatic and Aromatic Hydroxycarboxylates: A Combined Experimental and Theoretical Study

“…As the Hartree–Fock exchange terms significantly contribute to the energetics, single-point calculations of all species are computed at the B3LYP/def2-TZVP (Th = def-TZVP) level. As ESI-MS data are in the gas phase and potentiometric measurements are performed in the aqueous phase, a continuum solvation model (COSMO) with ε = 80 (dielectric constant of water) is used to correct the gas phase free energies. − We successfully used this strategy for several speciation studies involving heavy metal ions, including those of actinide ions. − All calculations are performed with TURBOMOLE 7.2. , …”