Two compounds capable of intramolecular halogen bonding were studied by 15N, 13C, and 19F NMR spectroscopy. Fluorine atoms within the compounds were used to activate the iodine and bromine halogen bond donors and as spectroscopic handles. These two compounds were then compared to eight related control compounds. The 15N NMR showed the greatest effect of halogen bonding, with nitrogen atom halogen bond acceptors displaying chemical shift decreases of 6 ppm and 1 ppm in iodo- and bromo-functionalized systems, respectively. Similarly, 13C NMR spectra showed evidence of intramolecular halogen bonding in the alkynyl carbons of the 2-ethynylpyridine system, with chemical shifts up to 2.4 ppm different than related control compounds. The 19F nuclei provided a means to study the effects of solvents on halogen bonding by providing evidence of intramolecular halogen bonding in dilute samples. The magnitude of 19F chemical shift changes in different solvents was directly correlated to the strength of the halogen bond in solution. Halogen bond strengths were found to decrease in different solvents in the following order: cyclohexane &gt; toluene &gt; benzene &gt; dichloromethane &gt; acetone &gt; pyridine.

Intramolecular halogen bonding of fluorinated haloarenes in solution

249th National Meeting (2015)

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