title: Interlocked host anion recognition by an indolocarbazole-containing [2]rotaxane.
abstract: The design, synthesis, structure, and anion-binding properties of the first indolocarbazole-containing interlocked structure are described. The novel [2]rotaxane molecular structure incorporates a neutral indolocarbazole-containing axle component which is encircled by a tetracationic macrocycle functionalized with an isophthalamide anion recognition motif. (1)H NMR and UV-visible spectroscopies and X-ray crystallography demonstrated the importance of pi-donor-acceptor, CH...pi, and electrostatic interactions in the assembly of pseudorotaxanes between the electron-deficient tetracationic macrocycle and a series of pi-electron-rich indolocarbazole derivatives. Subsequent urethane stoppering of one of these complexes afforded a [2]rotaxane, which was shown by (1)H NMR spectroscopic titration experiments to exhibit enhanced chloride and bromide anion recognition compared to its non-interlocked components. Computational molecular dynamics simulations provide further insight into the mechanism and structural nature of the anion recognition process, confirming it to involve cooperative hydrogen-bond donation from both macrocycle and indolocarbazole components of the rotaxane. The observed selectivity of the [2]rotaxane for chloride is interpreted in terms of its unique interlocked binding cavity, defined by the macrocycle isophthalamide and indolocarbazole N-H protons, which is complementary in size and shape to this halide guest.
authors.affiliation: Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford, OX1 3TA UK.
authors.forename: Asha
authors.initials: A
authors.lastname: Brown
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Mullen
authors.forename: Jay
authors.initials: J
authors.lastname: Ryu
authors.forename: Michał J
authors.initials: MJ
authors.lastname: Chmielewski
authors.forename: Sérgio M
authors.initials: SM
authors.lastname: Santos
authors.forename: Vitor
authors.initials: V
authors.lastname: Felix
authors.forename: Amber L
authors.initials: AL
authors.lastname: Thompson
authors.forename: John E
authors.initials: JE
authors.lastname: Warren
authors.forename: Sofia I
authors.initials: SI
authors.lastname: Pascu
authors.forename: Paul D
authors.initials: PD
authors.lastname: Beer
mesh_terms: D000838:Anions / Q000737:chemistry*; D001665:Binding Sites; D002227:Carbazoles / Q000138:chemical synthesis / Q000737:chemistry*; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D007211:Indoles / Q000138:chemical synthesis / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D043862:Rotaxanes / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D000838:Anions; D002227:Carbazoles; D007211:Indoles; D043862:Rotaxanes; C041514:carbazole