Conductivity, Structures, Spectra, and Thermal Properties of Lithium and Sodium Tetracyanidoborates with Crown Ether Encapsulated Cations: Isolated Ions in [AI(12-crown-4)2][B(CN)4] and 1D Chains in [AI (15-crown-5)][B(CN)4] (AI = Li, Na)

In research activities toward new electrolyte materials for energy devices, the new tetracyanidoborates [Li(C8H16O4)2][B(CN)4] (1), [Na(C8H16O4)2][B(CN)4] (2), [Li(C10H20O5)][B(CN)4] (3), and [Na(C10H20O5)][B(CN)4] (4), which contain lithium and sodium metal cations coordinated by macrocyclic polyether molecules, were synthesized and characterized. Their structures were determined by single‐crystal X‐ray diffraction measurements. Compounds 1 and 2 form orthorhombic crystals built up from isolated ion pairs. The alkaline metal cation is coordinated by eight oxygen atoms of two 12‐crown‐4 (12Cr4) crown ether molecules. Compounds 3 and 4 crystallize in the monoclinic crystal system and are constructed from salt chains that extend in one direction. The Na compound has double rows of approximately face‐to‐face oriented complex cations, which are bridged by two CN groups of each tetracyanidoborate anion. The Li compound contains single strands. In both cases, each anion has two coordinated and two uncoordinated CN groups. The different bonding situations in all four compounds are characterized by IR, Raman, and NMR spectroscopy. Electrochemical spectroscopy was performed to obtain the overall specific conductivity of 1 and 3. Furthermore, differential scanning calorimetry (DSC) measurements revealed melting points below 200 °C and decomposition temperatures above 230 °C. Four new tetracyanidoborate salts, two of which have unusual chain structures, were synthesized and characterized. Thermal measurements proved them to be fairly stable compounds, and impedance measurements show that they have good conductivity.