Hydrothermal synthesis, structure, Raman spectroscopy, and self-irradiation studies of (CM)-C-248(IO3)(3)

摘要

The study of curium iodate, CM(103)3, was undertaken as part of a systematic investigation of the 4f- and 5f-elements' iodates. The reaction (CmCl3)-Cm-248 with aqueous H5IO6 Under mild hydrothermal conditions results in the reduction IO65- to IO3- anions, and the subsequent formation Of CM(103)3 single crystals. Crystallographic data are: (193 K, MoKalpha, lambda = 0.71073 Angstrom): monoclinic, space group P2(1)/c, a = 7.2014(7) Angstrom, b = 8.5062(9) Angstrom, = 13.4622(14) Angstrom, beta = 100.142(2)degrees, V = 811.76(14), Z = 4, R(F) = 2.11%, R-2(F-o(2)) = 4.43% for 119 parameters with 1917 reflections with I>2sigma(I). The structure consists of Cm3+ cations bound by iodate anions to form [Cm(IO3)(8)] units, where the local coordination environment around the curium centers can be described as a distorted dodecahedron. There are three crystallographically unique iodate anions within the structure; two iodates bridge between three Cm centers, and one iodate bridges between two Cm centers and has a terminal oxygen atom. The bridging of the curium centers by the iodate anions creates a three-dimensional structure. Three strong Raman bands with comparable intensities were observed at 846, 804, and 760cm(-1) and correspond to the I-O symmetric stretching of the three crystallographically distinct iodate ions. The Raman profile suggests a lack of inter-ionic vibrational Coupling of the I-O stretching, while intra-ionic coupling provides symmetric and asymmetric components that correspond to each iodate site. Repeated collection of X-ray diffraction data for a crystal of Cm(IO3)(3) over a period of time revealed a gradual expansion of the unit cell from self-irradiation. After 71 days, the new parameters were: a = 7.2132(7) Angstrom, b = 8.5310(8) Angstrom, c = 13.505(1) Angstrom, beta = 100.021(2)degrees, V = 818.3(2). (C) 2004 Elsevier Inc. All rights reserved.