Received 17 September 2013
The monoclinic form of trilithium dichromium(III) tris(orthophosphate), Li3Cr2(PO4)3, was prepared by the reactive halide flux method. The structure of the title compound is composed of a three-dimensional anionic framework with composition 3[Cr2(PO4)3]3- and Li+ ions situated in the empty channels. The rigid framework built up from CrO6 octahedra and PO4 tetrahedra is the same as that found in other monoclinic Li3M2(PO4)3 (M = Fe, Sc, V) phases. The three Li+ cations of Li3Cr2(PO4)3 are unequally disordered over six crystallographically different sites. The classical charge balance of the title compound can be represented as [Li+]3[Cr3+]2[P5+]3[O2-]12. Solid-state UV/Vis spectra indicate that the crystal filed splitting (0) of the Cr3+ ion is around 2.22 eV.
For the structures of Li3M2(PO4)3 (M = Fe, Sc, Cr, V), see: d'Yvoire et al. (1983); Verin et al. (1985); Maksimov et al. (1986). The structures of the orthorhombic form of Li3Cr2(PO4)3 have been investigated by Genkina et al. (1991). Structural studies of Li3V2(PO4)3 based on single-crystal data have been reported previously by Kee & Yun (2013). The general structural features of the monoclinic phases have been discussed by Patoux et al. (2003); Fu et al. (2010); Yang et al. (2010). For ionic radii, see: Shannon (1976).
Data collection: RAPID-AUTO (Rigaku, 2006); cell refinement: RAPID-AUTO; data reduction: RAPID-AUTO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: WinGX (Farrugia, 2012) and publCIF (Westrip, 2010).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: WM2772 ).
This research was supported by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (grant No. 2011-0011309).
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