We report the syntheses of dichloro-, dibromo-, and diiodopyromellitic diimides (X2PMDIs, X = Cl, Br, or I) and the identification of a two-point halogen-bonding motif reminiscent of the formation of carboxylic acid dimers. In the solid state superstructure of these compounds, there are belt-like assemblies of molecules held together by significant intermolecular halogen-oxygen interactions. While Cl2PMDI and Br2PMDI are found to crystallize isostructurally, the steric bulk of the iodine atoms in I2PMDI enforces an alternate mode of crystal packing in which halogen-p interactions define the superstructure. Furthermore, these electron-deficient molecules co-crystallize with electron-rich naphthalenes into charge transfer mixed stacks which are exhibit interstack halogen-bonding interactions. The two-point halogen-bonding motif of the X2PMDI molecules appears to operate orthogonally from hydrogen-bonding interactions and enables an additional element of structural control for crystal engineering purposes.

Two-point halogen bonding in 3,6-dihalopyromellitic diimides

248th National Meeting (2014)

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