Self-assembly and thermotropic liquid crystal properties of a hexavacant germanomolybdate: [Ge2Mo16O58]12−

Abstract

Two new hexavacant germanomolybdates, (H₂enMe)₃K₂[Ge₂Mo₁₆O₅₈]·4H₃O·9H₂O (1) (enMe = 1,2-propanediamine) and Na₁₂[Ge₂Mo₁₆O₅₈]·30H₂O (2), were synthesized through the conventional aqueous method and characterized by X-ray crystallography, elemental analysis, IR spectra and thermogravimetry (TG) analysis. The polyoxoanions in compounds 1 and 2 contain two trivacant Keggin {β-A-GeMo₉O₃₄} units fused together by two {MoO₆} octahedra. This structural type is different from that of the well-known basic structural types and rarely observed in the POM chemistry. Further, DODACl was used as the surfactant to encapsulate the hexavacant polyoxoanion, resulting in the surfactant-encapsulated cluster (SEC) [DODA]₁₂[Ge₂Mo₁₆O₅₈]·16H₂O (SEC-Mo₁₆). Polarized optical microscopy, differential scanning calorimetry (DSC), variable temperature X-ray diffraction (VT-XRD) and transmission electron microscopy (TEM) revealed that SEC-Mo₁₆ exhibits characteristic thermotropic liquid crystal properties.