Single crystal growth and characterization of the first reduced lanthanum molybdenum oxychloride, La20Mo12O63Cl4, with an unusual trigonal prismatic MoO6 unit

• Single crystals of La20Mo12O63Cl4 were grown from a chloride melt.
• Purity was confirmed via powder X-ray diffraction.
• La20Mo12O63Cl4 crystallizes in a new structure type containing unusual MoO6 trigonal prisms.
• Optical properties were studied via UV/Vis spectroscopy.
• Magnetic properties were studied via susceptibility.

The use of a KCl/CsCl alkali eutectic flux under reducing conditions facilitated the crystal growth of the mixed valent Mo(V)/Mo(VI) compound La20Mo12O63Cl4. La20Mo12O63Cl4 crystallizes in the noncentrosymmetric hexagonal space group P-62m with a = 10.2241(2) Å and c = 15.0768(4) Å, which represents a new structure type exhibiting a three-dimensional crystal structure containing three different molybdenum coordination environments, MoO5 square pyramids, MoO6 trigonal prisms, and MoO5 trigonal bipyramids. The temperature dependence of the magnetic susceptibility was measured and La20Mo12O63Cl4 was found to be paramagnetic across the entire 2–300 K temperature range measured. Although noncentrosymmetric, La20Mo12O63Cl4 was not found to be second harmonic generation active. La20Mo12O63Cl4 was further characterized by UV/Vis spectroscopy.

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