Alkylammonium cation interactions with calixarene anions. Part 2. Structural characterisation of a salt of 2:3 cation: calixarene stoichiometry

Abstract

A room temperature single crystal X-ray structure determination on the tetramethylammonium ‘salt’ of calix[4]arene ([1.1.1.1]metacyclophane-7,14,21,28-tetraol) has revealed an unusual stoichiometry and unusual structure for this compound. Crystals of salt are tetragonal, space group P4/nnc, a= 18.230(4), c= 22.897(6)Å, Z= 4 f.u.; the structure was refined to a residual of 0.087 for 1471 ‘observed’[I > 3σ(I)] reflections. The solid has the composition LH₄·2[NMe₄]⁺[LH₃]^–·H₂O (LH₄= calix[4]arene) and contains the cation, ‘C’, in two distinct environments, both involving inclusion within the calixarene units but one involving simple inclusion by a single calixarene (‘A’) and the other encapsulation by a facing pair of symmetry-related calixarene entities (‘B’). Interaggregate spacings by lattice water molecules, W, result in the ‘A’ moieties being stacked up the 4 axis ⋯ WACCAW ⋯, while the ‘B’ moieties are stacked along the 2 axes in the ab diagonal, ⋯ W′BCBW′.