Ionic Clathrate Hydrates of Tetra-n-Butylammonium Nitrate (TBANO3) and Mixed TBA(NO3,OH): Novel Superstructures of Tetragonal Structure I

Abstract

The structures of an ionic clathrate hydrate of tetra-n-butylammonium nitrate TBANO₃·26.7H₂O and mixed TBA(NO₃)_1−x(OH)_x·(31.5 − x)H₂O hydrate obtained from a mixture of tetra-n-butylammonium nitrate and tetra-n-butylammonium hydroxide are determined by single crystal X-ray diffraction. These structures are new types of superstructures based on classical tetragonal structure I with four- and twofold unit cells volumes for TBANO₃·26.7H₂O and TBA(NO₃)_1−x(OH)_x·(31.5 − x)H₂O respectively. The superstructures form as a result of ordering in the arrangement of multicompartment cavities of the water-anionic framework. A TBA cation is displaced from the center of combined cavities due to the anisotropic environment of the anions, which leads to an additional symmetry reduction. The modes of the nitrate anion incorporation into the water framework of ionic clathrate hydrates are determined for the first time.