Synthesis and crystal structure of the pyridinium acid nitrate [(PyH)2(NO3)][H2(NO3)3] containing a dihydrogen trinitrate anion

A new protic room-temperature ionic liquid (T_c=14 ± 1°C) – pyridinium hydrogen dinitrate – was obtained from a solution of pyridinium nitrate in anhydrous nitric acid in a desiccator with P₂O₅. According to single crystal X-ray diffraction data, the solid state structure of [(PyH)₂(NO₃)][H₂(NO₃)₃] consists of hydrogen bonded cations [(PyH)₂(NO₃)]⁺ and anions [(NO₃)(HNO₃)₂]⁻ with a previously unknown configuration containing two HNO₃ molecules linked via hydrogen bonds to the central NO₃^- anion by the sin–anti type.