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Issue 33, 2009
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Halide binding in laterally non-symmetric aza-oxa cryptands through N/O/C–H⋯halide interactions with characterization of small water clusters

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Abstract

The structural study of halide complexes has been performed on two laterally non-symmetric aza-oxa cryptands Loo and Lmm having different cavity dimensions. For the fluoride complex of Loo, the ‘oxa’ end bridgehead N atom gets protonated to pull the internal fluoride towards the ‘oxa’ end. While bromide remains outside the cavity either by being sandwiched between the opposite-side directed arms of the two different moieties or by being incorporated into the space provided by the two same-side directed arms of a single Loo. In comparison, Lmm having a higher cavity dimension can accommodate chloride and bromide in addition to fluoride in its cavity. While Loo changes its conformation for its bromide complex attaining a ‘Y’-shaped architecture, cryptand Lmm retains its symmetrical pinwheel shape viewed down the C3 axis joining the two bridgehead amines throughout all of its halide complexes. While encapsulated fluoride resides at the ‘oxa’ end of Loo, the encapsulated fluoride/chloride/bromide of Lmm is displaced far away from the ‘oxa’ end to the ‘aza’ end. However, iodide remains outside the cavity for both cryptands. Two discrete water heptamers of acyclic and cyclic/acyclic configurations have been characterised by X-ray diffraction. Discrete water trimer, tetramer and adamantanoid clusters have also been identified within these organic crystal hosts.

Graphical abstract: Halide binding in laterally non-symmetric aza-oxa cryptands through N/O/C–H⋯halide interactions with characterization of small water clusters

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Publication details

The article was received on 03 Feb 2009, accepted on 19 May 2009 and first published on 11 Jul 2009


Article type: Paper
DOI: 10.1039/B902270H
Dalton Trans., 2009, 6496-6506

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    Halide binding in laterally non-symmetric aza-oxa cryptands through N/O/C–H⋯halide interactions with characterization of small water clusters

    M. C. Das, S. K. Ghosh and P. K. Bharadwaj, Dalton Trans., 2009, 6496
    DOI: 10.1039/B902270H

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