title: The curium aqua ion.
abstract: The coordination environment of the hydrated Cm3+ ion is probed both in the solid state and in solution. The analysis of single-crystal X-ray diffraction data from [Cm(H2O)9](CF3SO3)3 determines that the Cm species is surrounded by nine coordinating waters with a tricapped-trigonal-prismatic geometry involving six short Cm-O distances at 2.453(1) A and three longer Cm-O distances at 2.545(1) A. The Cm nona-aqua triflate is isostructural with the series of lanthanide and actinide [R(H2O)9](CF3SO3)3 (R=La-Lu, Pu) compounds. A similar nona-aqua geometry is seen for the coordination environment of Cm in aqueous solution, as probed by high-energy X-ray scattering and extended X-ray absorption fine structure spectroscopy, although the splitting in the first coordination shell is increased from 0.092(2) in the solid to 0.16(2) A in solution. This increase in splitting of the Cm-water distances in the first coordination sphere is discussed in terms of its potential relevance to the previously observed decrease in coordinating waters with decreasing ionic radius about the f-ion in solution.
authors.affiliation: Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439, USA. Skantha@anl.gov
authors.forename: S
authors.initials: S
authors.lastname: Skanthakumar
authors.forename: Mark R
authors.initials: MR
authors.lastname: Antonio
authors.forename: Richard E
authors.initials: RE
authors.lastname: Wilson
authors.forename: L
authors.initials: L
authors.lastname: Soderholm