Configuration of the dimolybdate in salt inclusion type of compounds, Cs2Mo2O7 ⋅ CsX (X=Cl, Br, and I)

Abstract

AbstractCs2Mo2O7 ⋅ CsI is obtained as a member of the series Cs2Mo2O7 ⋅ CsX with X=Cl, Br, and I from the synthesis of Cs2MoO4 with MoO3 and CsX. At room temperature, the compounds crystallize in the space group P63/mmc with the dimolybdate, [Mo2O7]2−, in a linear and eclipsed conformation. Low temperature Raman spectroscopy and low temperature X‐ray diffraction were used to investigate the effect of the hetero‐honeycomb lattice on the bridging angle of the dimolybdate. For X=Cl, a phase transition occurs below 150 K (P63/mmc → Cmcm). The phase transition relates to a lock‐in that involves bending of the (Mo−O−Mo) bridge. For the Pearson softer iodide compound, no phase transition is observed down to 4 K; thus, the linear configuration remains stable. Specific heat data and their evaluation in terms of phonon contributions are given.