title: Monomers, Dimers, and Helices: Complexities of Cerium and Plutonium Phenanthrolinecarboxylates.
abstract: 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 L3,2-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.
authors.affiliation: Department of Chemistry and Biochemistry, Florida State University , 95 Chieftan Way, Tallahassee, Florida 32306, United States.
authors.forename: Samantha K
authors.initials: SK
authors.lastname: Cary
authors.affiliation: Chemistry Divisions, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: Maryline G
authors.initials: MG
authors.lastname: Ferrier
authors.affiliation: National High Magnetic Field Laboratory , Tallahassee, Florida 32310, United States.
authors.forename: Ryan E
authors.initials: RE
authors.lastname: Baumbach
authors.affiliation: Department of Chemistry and Biochemistry, Florida State University , 95 Chieftan Way, Tallahassee, Florida 32306, United States.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Silver
authors.affiliation: School of Earth, Energy, and Environmental Science, Stanford University , Stanford, California 94305, United States.
authors.forename: Juan
authors.initials: J
authors.lastname: Lezama Pacheco
authors.affiliation: Chemistry Divisions, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: Stosh A
authors.initials: SA
authors.lastname: Kozimor
authors.affiliation: Chemistry Divisions, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: Henry S
authors.initials: HS
authors.lastname: La Pierre
authors.affiliation: Chemistry Divisions, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: Benjamin W
authors.initials: BW
authors.lastname: Stein
authors.affiliation: Department of Chemistry and Biochemistry, Florida State University , 95 Chieftan Way, Tallahassee, Florida 32306, United States.
authors.forename: Alexandra A
authors.initials: AA
authors.lastname: Arico
authors.affiliation: Department of Chemistry, George L. Clark X-ray Facility & 3M Materials Laboratory, University of Illinois , 505 South Mathews Avenue, Urbana, Illinois 61801, United States.
authors.forename: Danielle L
authors.initials: DL
authors.lastname: Gray
authors.affiliation: Department of Chemistry and Biochemistry, Florida State University , 95 Chieftan Way, Tallahassee, Florida 32306, United States.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Albrecht-Schmitt