title: Slow anion exchange, conformational equilibria, and fluorescent sensing in venus flytrap aminopyridinium-based anion hosts.
abstract: The synthesis, anion binding, and conformational properties of a series of 3-aminopyridinium-based, tripodal, tricationic hosts for anions are described. Slow anion and conformational exchange on the (1)H NMR time scale at low temperature, coupled with NMR titration, results in a high level of understanding of the anion-binding properties of the compounds, particularly with respect to significant conformational change resulting from induced fit complexation. Peak selectivity for halides, particularly Cl(-), is observed. The approach has been extended to dipodal and tripodal podands based on 3-aminopyridinium "arms" containing photoactive anthracenyl moieties. The 1,3,5-tripodal host shows a remarkable selectivity for acetate over other anions, in contrast to the analogous unsubstituted tris(3-aminopyridinium) analogue, despite the fact that low-temperature (1)H NMR experiments reveal a total of four acetate-binding conformations. Photodimerization of anthracene units results in the formation of potential fluorescent anion sensors.
authors.affiliation: Department of Chemistry, King's College London, Strand, UK.
authors.forename: Karl J
authors.initials: KJ
authors.lastname: Wallace
authors.forename: Warwick J
authors.initials: WJ
authors.lastname: Belcher
authors.forename: David R
authors.initials: DR
authors.lastname: Turner
authors.forename: Kauser F
authors.initials: KF
authors.lastname: Syed
authors.forename: Jonathan W
authors.initials: JW
authors.lastname: Steed