MOLECULAR MECCANO, PART-24 - MULTIPLY STRANDED AND MULTIPLY ENCIRCLEDPSEUDOROTAXANES

The self-assembly of four multicomponent rotaxane-like complexes, in w hich either (a) three or four dibenzo[24]crown-8 rings encircle thread like oligoammonium cations [PhCH2(NH2+CH2C6H4CH2)(n)NH2+CH2Ph] (n = 2 or 3) to form multiply encircled pseudorotaxanes, or (b) three or four dibenzylammonium ions an threaded simultaneously through large macroc yclic polyethers, viz., tris-p-phenylene[51]crown-15 and tetrakis-p-ph enylene[68]crown-20, to give multiply stranded pseudorotaxanes, is des cribed. These supramolecular entities are created on account of stabil izing [N+-H ... O] and [C-H ... O] hydrogen bonds, supplemented occasi onally by aromatic face-to-face and edge-to-face interactions, and [C- H ... F] intermolecular bonds. Evidence for the existence of these div erse pseudorotaxane architectures in solution, in the solid state, and in some cases, in the ''gas phase'', is provided by H-1 MMR spectrosc opy, X-ray crystallography, and mass spectrometry, respectively.