Crystal structure of 1,10-diazonia-18-crown-6 bis(hydrogen oxalate) and 1,10-diazonia-18-crown-6 oxalate dihydrate

An X-ray diffraction study has been performed to strudy the crystal structure of 1,10-diazonia-18-crown-6 bis(hydrogen oxalate) [H(2)DA18C6](2+). 2C(2)HO(4)(-) (I) and 1,10-diazonia-18-crown-6 oxalate dihydrate [H(2)DA18C6](2). 2C(2)O(4). 2H(2)O (II). Crysrals I are triclinic: space group PI, a = 7.825, b = 7.861, c = 9.349 Angstrom, alpha = 97.28, beta = 110.22, gamma = 99.12 degrees, Z = 1. Crystals II are monoclinic: space group P2(1)/n, a = 8.783, b = 10.640, c 10.225 Angstrom, beta = 97.04 degrees, Z = 2, The structures of I and II were solved by direct methods and refined by the full-matrix least-squares procedure, anisotropically to R = 0.036 (I) and 0.042 (II) for all 2206 (I) and 1990 (II) unique reflections measured (CAD-4 automatic diffractometer, lambda cuK(alpha)). In the crystal structures, the ionic complexes (salts) I and II are not individual "guest-host" complex molecules bur are parts of complex (infinite in two directions) three-dimensional layers of H-bonded molecular onions and DA18C6 dications (and water molecules in II). In structures I and II, the centrosymmetric DA18C6 dications have different conformations: two-angle in I and four-angle in IF. The unusual four-angle conformation of the DA18C6 dication was found for rite first lime.