title: Why is uranyl formohydroxamate red?
abstract: The complexation of UO2(2+) by formohydroxamate (FHA(-)) creates solutions with dark red coloration. The inherent redox activity of formohydroxamate leads to the possibility that these solutions contain U(V) complexes, which are often red. We demonstrate that the reaction of U(VI) with formohydroxamate does not result in reduction, but rather in formation of the putative cis-aquo UO2(FHA)2(H2O)2, whose polymeric solid-state structure, UO2(FHA)2, contains an unusually bent UO2(2+) unit and a highly distorted coordination environment around a U(VI) cation in general. The bending of the uranyl cation results from unusually strong π donation from the FHA(-) ligands into the 6d and 5f orbitals of the U(VI) cation. The alteration of the bonding in the uranyl unit drastically changes its electronic and vibrational features.
authors.affiliation: †Department of Chemistry and Biochemistry, Florida State University, 102 Varsity Way, Tallahassee, Florida 32306, United States.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Silver
authors.affiliation: ‡P. Roy and Diana T. Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104, United States.
authors.forename: Walter L
authors.initials: WL
authors.lastname: Dorfner
authors.affiliation: †Department of Chemistry and Biochemistry, Florida State University, 102 Varsity Way, Tallahassee, Florida 32306, United States.
authors.forename: Samantha K
authors.initials: SK
authors.lastname: Cary
authors.affiliation: †Department of Chemistry and Biochemistry, Florida State University, 102 Varsity Way, Tallahassee, Florida 32306, United States.
authors.forename: Justin N
authors.initials: JN
authors.lastname: Cross
authors.affiliation: †Department of Chemistry and Biochemistry, Florida State University, 102 Varsity Way, Tallahassee, Florida 32306, United States.
authors.forename: Jian
authors.initials: J
authors.lastname: Lin
authors.affiliation: ‡P. Roy and Diana T. Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104, United States.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Schelter
authors.affiliation: †Department of Chemistry and Biochemistry, Florida State University, 102 Varsity Way, Tallahassee, Florida 32306, United States.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Albrecht-Schmitt