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In the presence of methanol the tetrakis(benzoxazines) complex tetramethylammonium cation within the cavity, and the cavity is completely sealed by two intramolecular hydrogen bonds between amide groups. The Cl(-) anion is found external to the cavity. In CHCl(3), Me(4)N(+) is complexed within the cavity, but the Cl(-) anion acts as a stopper in the upper rim of the cavity, hydrogen-bonded to the amide groups. The solution results are supported by single-crystal X-ray structural studies of both the single-molecule molecular capsules, and those stoppered by Cl(-).
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Atwood et al. (2002) studied this question.
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