Anomalous halogen bonds in the crystal structures of 1,2,3-tri­bromo-5-nitro­benzene and 1,3-di­bromo-2-iodo-5-nitro­benzene

[摘要] The title trihalogenated nitro­benzene derivatives, C6H2Br3NO2 and C6H2Br2INO2, crystallize in triclinic and monoclinic cells, respectively, with two mol­ecules per asymmetric unit in each case. The asymmetric unit of the tri­bromo compound features a polarized Brδ+⋯Brδ- inter­molecular halogen bond. After substitution of the Br atom in the para position with respect to the nitro group, the network of X⋯X halogen contacts is reorganized. Two inter­molecular polarized halogen bonds are then observed, which present the uncommon polarization Brδ+⋯Iδ-: the more electronegative site (Br) behaves as a donor and the less electronegative site (I) as an acceptor for the charge transfer.

[学科分类] 数学（综合）

[关键词] CRYSTAL STRUCTURE;POLYHALOGENATED BENZENE;HALOGEN BOND;BROMINE;IODINE