Disordered crystal structure of 4,7,13,16,21,24-hexaoxa-1-aza-10-azoniabicyclo[8.8.8]hexacosane isocyanurate

Abstract

X-ray spectral analysis has been applied to study the crystal structure of 4,7,13,16,21,24-hexaoxa-1-aza-10-azoniabicyclo[8.8.8]hexacosane isocyanurate of an unusual composition: [H_1.2(Crypt-222)]^1,2+ · [H_0.8(Crypt-222)]^0.8+·2(C₃H₂N₃O₃)⁻ (I). The structure of I (space group C2/c, a = 37.840 Å, b = 13.760 Å, c = 19.456 Å, β = 91.21°, Z = 8) was solved by a direct method and refined by the full-matrix least-squares technique in the anysotropic approximation up to R = 0.119 over 6500 independent reflections measured (autodiffractometer CAD-4, λ-MoK _α). The structure of I has two independent cations of 2.2.2-cryptand linked by the proximate pseudo-center of inversion and they have a rare conformation of exo-exo type, in which H atom or lone pair at both their node atoms N are directed outward their cavity. In the structure of I, all H atoms at N atoms of cations and half of H atoms of isocyanurate anions are disordered and have the populations of positions 0.7, 0.5, and 0.3. There is a developed system of interionic hydrogen bonds in the crystal structure of I.