Crystal structures of the triiodide salt-molecule complexes (Xanthotoxin)2 · KI3 and (Glycine)4 · KI3

Abstract (Xanthotoxin)2 · KI3 is triclinic, a = 9.59(1), b = 11.09(1), c = 7.96(1) Å, α = 118.1(1), β = 86.7(1), γ = 114.5(1)°, Z = 1, P1̄. The structure determination is based on about 1900 reflection intensities (graphite-monochromated MoKα, Stoe two-circle diffractometer). The crystal contains columns of alternating K+ and [unk] ions, both located at crystallographic centres of symmetry. These columns (axes along [001]) are surrounded by stacks of xanthotoxin molecules, successive xanthotoxins within a stack being antiparallel. There are no direct iodine–iodine interactions and (xanthotoxin)2 · KI3 has a structure typical of complexes formed by inorganic salts and organic molecules. (Glycine)4 · KI3 is monoclinic, a = 22.946(6), b = 10.672(3), c = 8.230(3) Å, β = 91.54(8)°, Z = 4, C2/c. The glycine molecules are in the zwitterionic form and are arranged in sheets parallel to (100) in which the primary interactions are N-H–O hydrogen bonds and K+ –O electrostatic interactions. The K+ ions are enclosed in distorted Archimedean antiprisms of oxygens. The triiodide ions are in sheets parallel to and interleaving the glycine-K+ sheets and thus the overall structure is similar to the alternating arrangement of positively and negatively charged sheets found in some other polyiodide (and other types of) salts. There are weak I–I interactions within the triiodide sheets [d(I–I) = 3.982(0) Å].