Relativistic DFT and experimental studies of mono- and bis-actinyl complexes of an expanded Schiff-base polypyrrole macrocycleElectronic supplementary information (ESI) available: Table of formulas and abbreviations of the investigated complexes (Table S1); tables of calculated and experimental values of the THF-solvated complexes (S2); tables of optimised geometry parameters of B-pyU and B-U in various approaches (S3) and of pyridine-free actinyl complexes (S4 and S5); table of X-ray crystallog

• Main Authors: Zheng, Xiu-Jun, Bell, Nicola L, Stevens, Charlotte J, Zhong, Yu-Xi, Schreckenbach, Georg, Arnold, Polly L, Love, Jason B, Pan, Qing-Jiang
• Format: Journal Article
• Language: English
• Published: 12.10.2016
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c6dt01625a

The computationally- and experimentally-determined molecular structures of a bis-uranyl( vi ) complex of an expanded Schiff-base polypyrrolic macrocycle [(UO 2 ) 2 (L)] are in close agreement only if the pyridine in the fifth equatorial donor site on the uranium is included in the calculations. The relativistic density functional theory (DFT) calculations presented here are augmented from those on previously reported simpler frameworks, and demonstrate that other augmentations, such as the incorporation of condensed-phase media and the changes in the peripheral groups of the ligand, have only a slight effect. Synthetic routes to pure samples of the bis- and mono-uranyl( vi ) complexes have been developed using pyridine and arene solvents, respectively, allowing the experimental determination of the molecular structures by X-ray single crystal diffraction; these agree well with the calculated structures. A comprehensive set of calculations has been performed on a series of actinyl AnO 2 n + complexes of this macrocyclic ligand. These include both bis- and mono-actinyl adducts for the metals U, Np and Pu, and formal oxidation states VI and V. The reduction potentials of the complexes for U, Np, and Pu, incorporating both solvation and spin-orbit coupling considerations, show the order Np > Pu > U. The agreement between experimental and computed data for U is excellent, suggesting that at this level of computation predictions made about the significantly more radiotoxic Np and Pu molecules should be accurate. A particularly unusual structure of the mononuclear plutonyl( v ) complex was predicted by quantum chemical calculations, in which a twist in the macrocycle allows one of the two endo -oxo groups to form a hydrogen bond to one pyrrole group of the opposite side of the macrocycle, in accordance with this member of the set containing the most Lewis basic oxo groups. Relativistic DFT calculations present accurate geometries of complexes and redox properties, confirmed by the newly-developed experimental syntheses.