title: First pseudorotaxane-like [3]complexes based on cryptands and paraquat: self-assembly and crystal structures.
abstract: A new cryptand, bis(1,3,5-phenylene)tri(1,4,7,10-tetraoxadecyl) (3a), has been synthesized in good yield from bis(5-hydroxy-1,3-phenylene)-26-crown-8 (2a) and tri(ethylene glycol) ditosylate using pseudo-high dilution conditions. 3a forms a strong 1:1 complex with paraquat (1) in acetone solution with a high apparent association constant, 1.4 x 10(4) M(-)(1). A stoichiometry of 1:1 was also observed by mass spectrometry in the gaseous state. However, in the solid state, as determined by X-ray crystallography, the two complexes of 3a and the previously reported homologous cryptand, bis(1,3,5-phenylene)tri(1,4,7,10,13-pentaoxatridecyl) (3b), with paraquat (1) have 2:1 stoichiometry. A unique feature of these trimolecular pseudorotaxane-like complexes is that the guest occupies parts of the cavities of two cryptand molecules. For the first time it was found that in cryptand-based complexes, different stoichiometries are possible for the same host-guest pair.
authors.affiliation: Department of Chemistry, Virginia Polytechnic Institute & State University, Blacksburg, Virginia 24061, USA.
authors.forename: Feihe
authors.initials: F
authors.lastname: Huang
authors.forename: Harry W
authors.initials: HW
authors.lastname: Gibson
authors.forename: William S
authors.initials: WS
authors.lastname: Bryant
authors.forename: Devdatt S
authors.initials: DS
authors.lastname: Nagvekar
authors.forename: Frank R
authors.initials: FR
authors.lastname: Fronczek