Solution stoichiometry determines crystal stoichiometry in halogen-bonded supramolecular complexes

Abstract

The behavior of the methylisonicotinate (MINC) building block as halogen bonding-acceptor module has been investigated in the solid state. Both the N and the O atoms of MINC interact with the iodine atoms of 1,4-diiodotetrafluorobenzene (DITFB) giving rise to N⋯I and O⋯I interactions. Hierarchy between these interactions allows the control of the composition and thus the structure of the supramolecular complex, according to the composition of the reaction mixture. A structure based on an infinite chain and a trimeric supermolecule have been obtained starting from a 1 ∶ 1 MINC/DITFB stoichiometry or by using a large excess of MINC, respectively. While the former structure shows simultaneous N⋯I and O⋯I halogen bonds, only N⋯I interactions are present in the latter one. The results also elicit some general considerations based on the rare chain morphology shown by the 1 ∶ 1 complex.