Observation of strong halogen bonds in the solid state structures of bis-haloimidazolium macrocycles

Abstract

Two new bis-haloimidazolium macrocycles are described, containing either chloro or iodoimidazolium heterocycles. Crystal structure determinations of these macrocycles as their bromide salts are reported, as well as of the nitrate salt of the analogous bis-bromoimidazolium macrocycle. In all structures, short halogen bonds are observed in the solid state, with the nitrate complex of the bis-bromoimidazolium macrocycle containing a particularly short C–Br⋯O halogen bond. A comparison of the observed halogen bonds with related structures in the Cambridge Structural Database reveals only one halogen bond to an oxoanion shorter than that in the bromoimidazolium⋯nitrate complex, and that this is the shortest halogen bond from a bromine donor.