Structure and spectroscopy of uranyl and thorium complexes with substituted phosphine oxide ligands

Andrew T. Breshears 1 , Charles L. Barnes 1 , Durgesh V. Wagle 1 , Gary A. Baker 1 , Michael K. Takase 2 ,  and Justin R. Walensky 1
  • 1 Department of Chemistry, University of Missouri, Columbia, MO 65211, USA
  • 2 Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA


Phosphine oxide ligands are important in the chemistry of the nuclear fuel cycle. We have synthesized and characterized a series of phosphine oxide ligands with polycyclic aromatic hydrocarbon (PAH) groups to enhance the spectroscopic features of uranyl, UO22+, and to make detection more efficient. Complexation of OPPh2R, R = C10H7 (naphthyl); C14H9 (phenanthrenyl); C14H9 (anthracenyl); and C16H9 (pyrenyl), to UO2(NO3)2 afforded the eight-coordinate complexes, UO2(NO3)2(OPPh2R)2. An eleven-coordinate complex, Th(NO3)4[OPPh2(C14H9)]3, C14H9 = phenanthrenyl, was structurally characterized, and was found to be the first thorium compound isolated with three phosphine oxide ligands bound. The phosphine oxide ligands were not fluorescent but the anthracenyl-substituted ligand showed broad, red-shifted emission at approximately 50 nm relative to typical anthracene, making this ligand set a possibility for use in detection. The synthesis and spectroscopy of the uranyl and thorium complexes are presented.

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Radiochimica Acta publishes original papers, review articles, and “rapid communications” (short articles of a more timely interest) on all chemical aspects of nuclear science and technology. The journal is geared toward scientists who are actively engaged in research work.