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. H-1 NMR and UV-visible spectroscopies and X-ray crystallography demonstrated the importance of pi-donor-acceptor, CH center dot center dot center dot 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 H-1 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.
keywords
HYDROGEN-BONDING INTERACTIONS; NEUTRAL MACROCYCLIC AMIDES; INDOLE-BASED MACROCYCLES; X-RAY-DIFFRACTION; MOLECULAR MECCANO; DIHYDROGEN PHOSPHATE; ORGANIC-SOLVENTS; AQUEOUS-SOLUTION; CLICK CHEMISTRY; BINDING AGENTS
subject category
Chemistry
authors
Brown, A; Mullen, KM; Ryu, J; Chmielewski, MJ; Santos, SM; Felix, V; Thompson, AL; Warren, JE; Pascu, SI; Beer, PD
our authors
Sérgio Miguel Fernandes dos Santos
Assistant Researcher
Vítor Félix
Associate Professor with Aggregationacknowledgements
We thank Dr. N. H. Rees for NMR advice and the EPSRC for postdoctoral fellowships (K.M.M., M.J.C.) and a studentship (A.B.). S.M.S. acknowledges FCT for a Ph.D. grant (SFRH/BD/29596/2006). V.F. acknowledges the Fundacao para. a Ciencia e Tecnologia (FCT), with coparticipation of the European Community funds FEDER, for the financial support under project PTDC/QUI/68582/2006. S.I.P. thanks the Royal Society for funding and SRS Daresbury for a research grant to support crystallographic work.