Density Functional Theory Studies of Actinide(III) Motexafins (An-Motex²⁺, An = Ac, Cm, Lr). Structure, Stability, and Comparison with Lanthanide(III) Motexafins

Abstract

Newly developed relativistic energy-consistent 5f-in-core actinide pseudopotentials and corresponding (7s6p5d1f)/[5s4p3d1f] basis sets in the segmented contraction scheme, combined with density functional theory methods, have been used to study the molecular structure and chemical properties of selected actinide(III) motexafins (An-Motex2+, An = Ac, Cm, Lr). Structure and stability are discussed, and a comparison to the lanthanide(III) motexafins (Ln-Motex2+, Ln = La, Gd, Lu) is made. The actinide element is found to reside above the mean N5 motexafin plane, and the larger the cation, the greater the observed out-of-plane displacement. It is concluded that the actinium(III), curium(III), and lawrencium(III) cations are tightly bound to the macrocyclic skeleton, yielding stable structures. However, the calculated metal-ligand gas-phase binding energy for An-Motex2+ is about 1-2 eV lower than that of Ln-Motex2+, implying a lower stability of An-Motex2+ compared to Ln-Motex2+. Results including solvent effects imply that Ac-Motex2+ is the most stable complex in aqueous solution and should be the best candidate for experimentalists to get stable actinide(III) motexafin complexes.

Quasirelativistic 5f-in-core pseudopotential study of the actinocenes An(C8H8)2, An=Th–Pu

“…Besides the actinocene complexes studied here, the 5f-incore PPs yielded reasonable results for ionic compounds as fluorides [15,20] and for organometallic complexes as actinide(III) motexafins [34]. Moreover, they have successfully been used for actinide(III) mono-and polyhydrates [20,35].…”

Quasirelativistic energy-consistent 5f-in-core pseudopotentials for trivalent actinide elements

“…In preliminary studies of actinide(III) motexafin complexes (An-Motex 2+ , An = Ac, Cm, Lr) at the level of gradient corrected hybrid density functional theory (DFT/B3LYP), the 5f-in-core approach already performed encouragingly well [17]. A similar statement holds for yet unpublished studies of the hydration behaviour of trivalent actinide ions [18].…”

A Time-Dependent Density Functional Study of a Non-Aromatic [1.1.1.1.1]-Pentaphyrin and Its Lutetium Complex

“…26,27 For the molecular optimizations, the SV(P) split-valence basis set of Ahlrichs et al was used, which includes polarization functions on C, N, O, and Si atoms. 28 The Stuttgart pseudopotential (SDD) was used for the lutetium atom (including 60 core electrons), with the optimized valence basis set taken from ref 29. The vibrational analysis, carried out on the optimized structures, has given all real eigenvalues for the Hessian matrix.…”