X-ray structural study of lanthanide complexes with a p-tert-butylthiacalix[4]arene bearing phosphoryl pendant arms

A new lower-rim substituted thiacalix[4]arene, 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(diphenylphosphinoylmethoxy) thiacalix[4]arene (L) has been synthesized and structurally characterized as an adduct L·0.5MeOH·1.5H2O, monoclinic, space group P21/n. The ligand adopts a cone conformation. Trivalent lanthanide ion complexes of this ligand have been synthesized and characterized by elemental analysis and IR spectra. The crystal structures of La3+ and Nd3+ complexes were determined by X-ray diffraction method. They are isostructural and belong to tetragonal system, I41/acd space group. In each complex, the calixarene retains the cone conformation, the metal ion is nine-coordinated to four oxygen atoms from phosphine oxide substituents, four oxygen atoms from two bidentate nitrate anions and one oxygen atom from a hydroxyl ion. The coordination polyhedron is a single-capped square antiprism. The complex assembles to a novel infinitely 1D helical structure through π-π stacking, and further crosses each other forming a nanometer scale chessboard-like pore structure along c direction.