Crystal structure of 4,7,13,16,21,24-hexaoxa-1,10-diazoniabicyclo [8.8.8]hexacosane (2S,3S)-tartrate

Abstract

Crystal structure of (2S,3S)-tartrate of 4,7,13,16,21,24-hexaoxa-1,10-diazoniabicyclo-[8.8.8]hexacosane, [H₂(Crypt-222)]²⁺·(C₄H₄O₆)²⁻ (I) has been studied by single crystal X-ray diffraction. Triclinic structure of I (space group P1, a = 8.424 Å, b = 13.011 Å, c = 13.806 Å; α = 116.37°, β = 106.45°, γ = 91.81°; Z = 2) was solved by the direct method and refined in the full-matrix anisotropic approximation to R = 0.140 for 5850 measured independent reflections (automated diffractometer CAD-4, λMoK _α). In the structure of I, two independent dications of 2.2.2-cryptand (nitrogen atoms are protonated) are linked to the approximate inversion symmetry and have a rare conformation of exo-exo type, when two atoms sitting on N atoms are protruded out of their cavity. The centroids of two crystallographically unique (2S,3S)-tartrate dianions are bound with the same approximate inversion center. An extended system of hydrogen bonds is developed in the crystal of I.