Crystal packing of two 5‐substituted 2‐methyl‐4‐nitro‐1H‐imidazoles

Infinite chains connected by N—H...N hydrogen bonding form the primary packing motif in two closely related 4‐nitroimidazole derivatives, viz. 5‐bromo‐2‐methyl‐4‐nitro‐1H‐imidazole, C₄H₄BrN₃O₂, (I), and 2‐methyl‐4‐nitro‐1H‐imidazole‐5‐carbonitrile, C₅H₄N₄O₂, (II). These chains are almost identical, even though in (II) there are two symmetry‐independent molecules in the asymmetric unit. The differences appear in the interactions between the chains; in (I), there are strong C—Br...O halogen bonds, which connect the chains into a two‐dimensional grid, while in (II), the cyano group does not participate in specific interactions and the chains are only loosely connected into a three‐dimensional structure.