Theoretical exploration of uranyl complexes of a designed polypyrrolic macrocycle: Structure/property effects of hinge size on Pacman-shaped complexes

Qing-Jiang Pan, Samuel O. Odoh, Georg Schreckenbach, Polly L. Arnold, Jason B. Love

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

A polypyrrolic macrocycle with naphthalenyl linkers between the N4-donor compartments (L2) was designed theoretically according to its experimentally-known analogues with phenylenyl (L1) and anthracenyl (L3) linkers. The uranyl and bis(uranyl) complexes formed by this L2 ligand have been examined using scalar-relativistic density functional theory. The calculated structural properties of the mononuclear uranyl-L2 complexes are similar to those of their L1 counterparts. The binuclear L2 complexes exhibit a butterfly-like bis(uranyl) core in which a linear uranyl is coordinated in a side-by-side fashion to a cis-uranyl unit. The calculated U=O bond orders in the uranyl-L2 complexes indicate partial triple bonding character with the only exceptions being the U-Oendo bonds in the U2O4 core of the butterfly-shaped binuclear complexes. Overall, the bond orders agree with the trends in the calculated U=O stretching vibrational frequencies. Regarding the bis(uranyl) L1, L2 and L3 complexes, the phenylenyl-hinge L1 complexes adopt a butterfly-like and a T-shaped isomer in the oxidation state of U(VI), but only a butterfly-like one in the U(V), which differs from that of the naphthalenyl-hinge L2 complexes as well as the lateral twisted structure of the anthracenyl-hinge L3 complexes. The intramolecular cation-cation interactions are found in the L1 and L2 complexes, but are absent in the L3 complexes. Finally, using model uranyl transfer reactions from the L1 complexes, the formation of the mononuclear L2 complexes is calculated to be a slightly endothermic process. This suggests that it should be possible to synthesize the L2 complexes using similar protocols as employed for the L1 complexes.

Original languageEnglish
Pages (from-to)8878-8885
Number of pages8
JournalDalton Transactions
Volume41
Issue number29
Early online date11 Jun 2012
DOIs
Publication statusPublished - 7 Aug 2012

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