The study of curium iodate, Cm(IO
3)
3, was undertaken as part of a systematic investigation of the 4
f- and 5
f-elements’ iodates. The reaction of
248CmCl
3 with aqueous H
5IO
6 under mild hydrothermal conditions results in the reduction of IO
65− to IO
3− anions, and the subsequent formation of Cm(IO
3)
3 single crystals. Crystallographic data are: (193 K, Mo
Kα, ): monoclinic, space group
P2
1/
c, , , ,
β=100.142(2)°,
V=811.76(14),
Z=4,
R(
F)=2.11%, for 119 parameters with 1917 reflections with
I>2σ(
I). The structure consists of Cm
3+ cations bound by iodate anions to form [Cm(IO
3)
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 760 cm
−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(IO
3)
3 over a period of time revealed a gradual expansion of the unit cell from self-irradiation. After 71 days, the new parameters were: , , ,
β=100.021(2)°,
V=818.3(2).
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