Inorganic‐Organic Hybrid Crystals Derived from Polyoxovanadate and Ionic‐Liquid toward Promising Conductive Materials

Abstract Conductive polyoxovanadate inorganic‐organic hybrid crystals comprising alkaline earth metal (divalent) cations were successfully obtained with the use of an ionic‐liquid cation having imidazolium and methacryloyl moieties (denoted as MAImC₁). Two types of crystals containing decavanadate ([V₁₀O₂₈]⁶⁻, V₁₀) anion were obtained as [MAImC₁]₂Ca₂[V₁₀O₂₈] ⋅ 16H₂O ⋅ 2 C₂H₅OH (MAImC₁−Ca−V₁₀) and [MAImC₁]₂Mg₂[V₁₀O₂₈] ⋅ 18H₂O ⋅ 2 C₂H₅OH (MAImC₁−Mg−V₁₀). Connection modes of the divalent cations were different: Ca²⁺ cations were connected to V₁₀ to form a {[Ca(H₂O)₅]₂V₁₀O₂₈]}²⁻ anion in MAImC₁−Ca−V₁₀, while a discrete [V₁₀O₂₈]⁶⁻ and hydrated [Mg(H₂O)₆]²⁺ were present in MAImC₁−Mg−V₁₀. Conductivities under a fully humidified condition at 353 K (80 °C) were high values of 3.0×10⁻⁴ S cm⁻¹ for MAImC₁−Ca−V₁₀ and 3.3×10⁻³ S cm⁻¹ for MAImC₁−Mg−V₁₀, respectively. The higher conductivity under hydrated conditions suggests proton as a conductive carrier. The better conductivity of MAImC₁−Mg−V₁₀ is plausibly derived from the more effective hydrogen‐bonded network in the crystal lattice.