The title compound, C40H64O12, crystallizes in a pseudo-merohedrally twinned primitive monoclinic cell with similar contributions of the two twin components. There are two symmetry-independent half-mol-ecules of nona-ctin in the asymmetric unit. Each mol-ecule has a pseudo-S 4 symmetry and resides on a crystallographic twofold axis; the axes pass through the mol-ecular center of mass and are perpendicular to the plane of the macrocycle. The literature description of the room-temperature structure of nona-ctin as an order-disorder structure in an ortho-rhom-bic unit cell is corrected. We report a low-temperature high-precision ordered structure of free nona-ctin that allowed for the first time precise determination of its bond distances and angles. It possesses an unfolded and more planar geometry than its complexes with encapsulated Na +, K+, Cs+, Ca2+ or NH4 + cations that exhibit more isometric overall conformations.
|Journal||Acta Crystallographica Section C: Crystal Structure Communications|
|State||Published - 15 Oct 2009|