Monomers, Dimers, and Helices: Complexities of Cerium and Plutonium Phenanthrolinecarboxylates

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• 作者：Samantha K. Cary ; Maryline G. Ferrier ; Ryan E. Baumbach ; Mark A. Silver ; Juan Lezama Pacheco ; Stosh A. Kozimor ; Henry S. La Pierre ; Benjamin W. Stein ; Alexandra A. Arico ; Danielle L. Gray ; Thomas E. Albrecht-Schmitt
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：May 2, 2016
• 年：2016
• 卷：55
• 期：9
• 页码：4373-4380
• 全文大小：400K
• 年卷期：0
• ISSN：1520-510X

文摘

The reaction of Ce^III or Pu^III with 1,10-phenanthroline-2,9-dicarboxylic acid (PDAH₂) results in the formation of new f-element coordination complexes. In the case of cerium, Ce(PDA)(H₂O)₂Cl·H₂O (1) or [Ce(PDAH)(PDA)]₂[Ce(PDAH)(PDA)] (2) was isolated depending on the Ce/ligand ratio in the reaction. The structure of 2 is composed of two distinct substructures that are constructed from the same monomer. This monomer is composed of a Ce^III cation bound by one PDA^2– dianionic ligand and one PDAH^– monoanionic ligand, both of which are tetradentate. Bridging by the carboxylate moieties leads to either [Ce(PDAH)(PDA)]₂ dimers or [Ce(PDAH)(PDA)]_1∞ helical chains. For plutonium, Pu(PDA)₂ (3) was the only product isolated regardless of the Pu/ligand ratio employed in the reaction. During the reaction of plutonium with PDAH₂, Pu^III is oxidized to Pu^IV, generating 3. This assignment is consistent with structural metrics and the optical absorption spectrum. Ambiguity in the assignment of the oxidation state of cerium in 1 and 2 from UV–vis–near-IR spectra invoked the use of Ce L_3,2-edge X-ray absorption near-edge spectroscopy, magnetic susceptibility, and heat capacity measurements. These experiments support the assignment of Ce^III in both compounds. The bond distances and coordination numbers are also consistent with these assignments. 3 contains 8-coordinate Pu^IV, whereas the cerium centers in 1 and 2 are 9- and/or 10-coordinate, which correlates with the increased size of Ce^III versus Pu^IV. Taken together, these data provide an example of a system where the differences in the redox behavior between these f elements creates more complex chemistry with cerium than with plutonium.