Journal
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
Volume 135, Issue 10, Pages 3841-3854Publisher
AMER CHEMICAL SOC
DOI: 10.1021/ja308993g
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Funding
- EU [07-11]
- British Council French Alliance Program
- Alexander von Humboldt Foundation
- U.K. Engineering and Physical Sciences Research Council (EPSRC)
- European Commission Program Training and Mobility of Researchers
- Natural Sciences and Engineering Research Council of Canada (NSERC)
- LBNL LDRD program
- Office of Science, of the U.S. Department of Energy [DE-AC02-05CH11231]
- EPSRC [EP/G038945/1] Funding Source: UKRI
- Engineering and Physical Sciences Research Council [EP/G038945/1] Funding Source: researchfish
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The heterobimetallic complexes [{UO(2)Ln-(py)(2)(L)}(2)], combining a singly reduced uranyl cation and a rare-earth trication in a binucleating polypyrrole Schiff-base macrocycle (Pacman) and bridged through a uranyl oxo-group, have been prepared for Ln = Sc, Y, Ce, Sm, Eu, Gd, Dy, Er, Yb, and Lu. These compounds are formed by the single-electron reduction of the Pacman uranyl complex [UO2(py)(H2L)] by the rare-earth complexes Ln(III)(A)(3) (A = N(SiMe3)(2), OC6H3Bu2t-2,6) via homolysis of a Ln-A bond. The complexes are dimeric through mutual uranyl exo-oxo coordination but can be cleaved to form the trimetallic, monouranyl ate complexes [(py)(3)LiOUO(mu-X)Ln(py)(L)] by the addition of lithium halides. X-ray crystallographic structural characterization of many examples reveals very similar features for monomeric and dimeric series, the dimers containing an asymmetric U2O2 diamond core with shorter uranyl U=O distances than in the monomeric complexes. The synthesis by Ln(III)-A homolysis allows [5f(1)-4f(n)](2) and Li[5f(1)-4f(n)] complexes with oxo-bridged metal cations to be made for all possible 4f(n) configurations. Variable-temperature SQUID magnetometry and IR, NIR, and EPR spectroscopies on the complexes are utilized to provide a basis for the better understanding of the electronic structure of f-block complexes and their f-electron exchange interactions. Furthermore, the structures, calculated by restricted-core or all-electron methods, are compared along with the proposed mechanism of formation of the complexes. A strong antiferromagnetic coupling between the metal centers, mediated by the oxo groups, exists in the (USmIII)-Sm-V monomer, whereas the dimeric (UDyIII)-Dy-V complex was found to show magnetic bistability at 3 K, a property required for the development of single-molecule magnets.
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