Halogen-Bond-Assisted Guest Inclusion in a Synthetic Cavity (original) (raw)
Halogen bonding (XB) is an attractive interaction between electrophilic halogen atoms in organic halides and Lewis bases, such as amines, ketones, ethers, and nucleophilic anions. [1, 2] This type of interaction has attracted considerable interest, but most studies on XB reported to date have relied solely on solid-state observations [3] or theoretical predictions and interpretations. [4] Although they also exist in solution, halogen-bonded systems in liquid media have received much less attention. [5-7] Previously,the self-assembled cage 1 (Figure 1) was shown to accommodate molecular aggregates, such as DNA duplexes [8] and fluorous aggregates. [9] In the confined space of 1,weak interactions within the aggregates are enhanced, as observed by both NMR spectroscopy and X-ray crystallography.The solution structures (NMR) were consistently the same as the solid-state structures (X-ray). In this study,we investigated halogen-bonded systems in the cavity of cage 1. We observed clear XB between iodoperfluorocarbons 2 and 3 (XB donors) and NO 3 À anions and/or H 2 Omolecules (XB acceptors). Both NMR spectroscopic and X-ray crystallographic studies suggested that XB assists guest inclusion. We also observed the pair-selective inclusion of an aromatic
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