title: Isomeric 2,6-pyridino-cryptands based on dibenzo-24-crown-8.
abstract: Cryptands 4 and 5 were synthesized from cis- and trans-bis(hydroxymethylbenzo)-24-crown-8 by reaction with pyridine-2,6-dicarboxylic acid chloride in 42 and 48% yields, respectively. The new cryptands form pseudorotaxanes with the paraquat derivative N,N'-bis(beta-hydroxyethyl)-4,4'-bipyridinium bis(hexafluorophosphate) ("paraquat diol", 6): Ka=1.0x10(4) and 1.4x10(4) M-1, respectively. The cryptands also form complexes with ammonium hexafluorophosphate. Formation of the paraquat/cryptand-based pseudorotaxanes can be switched off and on in a controllable manner on the basis of the cryptands' abilities to complex KPF6 strongly, providing a new mechanism for control of molecular shuttles. K+ displaces paraquat diol from the cryptands, converting yellow-orange solutions to colorless; however, addition of 18-crown-6 binds the KPF6 and allows the colored cryptand-paraquat complex to reform. Crystal structures are reported for both cryptands, both paraquat diol-based pseudorotaxanes, both NH4PF6 complexes, and both KPF6 complexes.
authors: Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0212, USA. hwgibson@vt.edu
authors: Harry W
authors: HW
authors: Gibson
authors: Hong
authors: H
authors: Wang
authors: Carla
authors: C
authors: Slebodnick
authors: Joseph
authors: J
authors: Merola
authors: W Scott
authors: WS
authors: Kassel
authors: Arnold L
authors: AL
authors: Rheingold