Halogen bonding in 1,2-dibromo-4,5-dimethoxybenzene and 1,2-diiodo4,5-dimethoxybenzene

Abstract

An interesting case of 'halogen-bonding-promoted' crystal structure architecture is presented. The two title compounds, C8H8Br2O2 and C8H8I2O2, have almost indistinguishable molecular structures but very different spatial organization, and this is mainly due to differences in the halogen-bonding interactions in which the different species present, i.e. Br and I, take part. The dibromo structure exhibits a pi-bonded columnar array involving all four independent molecules in the asymmetric unit, with intercolumnar interactions governed by C-Br center dot center dot center dot Br-C links and with no C-Br center dot center dot center dot O/N interactions present. In the diiodo structure, instead, the C-I center dot center dot center dot O synthon prevails, defining linear chains, in turn interlinked by C-I center dot center dot center dot I-C interactions.