Interlocked host anion recognition by an indolocarbazole-containing [2]rotaxane

Reference:

Brown, A., Mullen, K. M., Ryu, J., Chmielewski, M. J., Santos, S. M., Felix, V., Thompson, A. L., Warren, J. E., Pascu, S. I. and Beer, P. D., 2009. Interlocked host anion recognition by an indolocarbazole-containing [2]rotaxane. Journal of the American Chemical Society, 131 (13), pp. 4937-4952.

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Official URL:

http://dx.doi.org/10.1021/ja809905x

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. 1H NMR and UV−visible spectroscopies and X-ray crystallography demonstrated the importance of π-donor−acceptor, CH···π, and electrostatic interactions in the assembly of pseudorotaxanes between the electron-deficient tetracationic macrocycle and a series of π-electron-rich indolocarbazole derivatives. Subsequent urethane stoppering of one of these complexes afforded a [2]rotaxane, which was shown by 1H 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.

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