Structures, electronic properties, hydration and UV-vis absorption spectra of actinide motexafins [An-Motex]²⁺ (An = Ac, Cm, Lr) and [UO₂-Motex]¹⁺: insights from DFT calculations

Abstract

Molecular and electronic structures and UV-vis spectra of selected actinide(III) motexafins ([An-Motex]²⁺, An = Ac, Cm, Lr) as well as of uranyl(IV) motexafin ([UO₂-Motex]⁺) were studied by using density functional theory methods combined with relativistic energy-consistent 5f-in-core actinide pseudopotentials. Solvent effects were considered by an explicit treatment of the first water coordination sphere in combination with the COSMO solvation model for bulk hydration effects. It is concluded that the Ac(III), Cm(III), Lr(III), and uranyl(IV) cations are tightly bound to the macrocyclic skeleton, yielding stable structures. By calculating the changes of the Gibbs free energies ΔG for the reactions X-Motex⁻ + Y → X + Y-Motex⁻ (X = La³⁺, Eu³⁺, Gd³⁺, Lu³⁺; Y = ${\text{UO}}_2^{2+}$, Am³⁺, Cm³⁺), it is found that although in aqueous solution the Motex⁻ ligand prefers Ln³⁺ (Ln = Eu, Gd, Lu) over An³⁺ (An = Am, Cm) it rather prefers ${\text{UO}}_2^{2+}$ over Ln³⁺ (Ln = La, Eu, Gd, Lu). The results suggest that motexafin might be useful for the separation of uranyl in nuclear waste treatments and possibly also for the treatment of uranyl poisoning in vivo. In particular motexafin might be a chelating agent for ²²⁵Ac³⁺ in targeted α-therapy.

GRAPHICAL ABSTRACT

KEYWORDS:

• Uranyl(IV) motexafins
• actinide(III) motexafins
• lanthanide(III) motexafins
• molecular structure
• electronic spectrum

Disclosure statement

No potential conflict of interest was reported by the author(s).

ORCID

Xiaoyan Cao http://orcid.org/0000-0002-3438-575X

Michael Dolg http://orcid.org/0000-0002-0538-0837

Additional information

Funding

The financial support of the Deutsche Forschungsgemeinschaft (DFG) CA 1390/1-1 is gratefully acknowledged.