Relativistic DFT and experimental studies of mono- and bis-actinyl complexes of an expanded Schiff-base polypyrrole macrocycle

Zheng, X.-J., Bell, N. L. , Stevens, C. J., Zhong, Y.-X., Schreckenbach, G., Arnold, P. L., Love, J. B. and Pan, Q.-J. (2016) Relativistic DFT and experimental studies of mono- and bis-actinyl complexes of an expanded Schiff-base polypyrrole macrocycle. Dalton Transactions, 45(40), pp. 15910-15921. (doi: 10.1039/C6DT01625A) (PMID:27373562)

Abstract

The computationally- and experimentally-determined molecular structures of a bis-uranyl(VI) complex of an expanded Schiff-base polypyrrolic macrocycle [(UO2)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 AnO2n+ 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.

• Item Type: Articles
• Additional Information: This work is supported by the National Natural Science Foundation of China (21273063) and the Scientific Foundations of State Education Ministry and Heilongjiang Province for the Returned Overseas Chinese Scholars. GS acknowledges financial support from the Natural Sciences and Engineering Research Council of Canada (NSERC, Discovery Grant). PLA thanks the Technische Universität München – Institute for Advanced Study, funded by the German Excellence Initiative; PLA and JBL thank the University of Edinburgh, and the Engineering and Physical Sciences Research Council EPSRC EP/M010554/1, EP/H004823/1, and EP/G038945/1.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Bell, Dr Nicola
• Authors: Zheng, X.-J., Bell, N. L., Stevens, C. J., Zhong, Y.-X., Schreckenbach, G., Arnold, P. L., Love, J. B., and Pan, Q.-J.
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: Dalton Transactions
• Publisher: Royal Society of Chemistry
• ISSN: 1477-9226
• ISSN (Online): 1477-9234
• Published Online: 28 June 2016
• Copyright Holders: Copyright © 2016 The Royal Society of Chemistry
• First Published: First published in Dalton Transactions 45(40): 15910-15921
• Publisher Policy: Reproduced in accordance with the publisher copyright policy