Crystal packing modes of 1-(40-aryl)-4-nitro-5-methylimidazoles: p-stacking, weak hydrogen bonds and C–Cl· · ·O halogen bonds

The crystal structures of four derivatives of 1-phenyl-4-nitro-5-methylimidazole have been determined by means of X-ray crystallography at 100(1) K. The interplay of different weak intermolecular interactions: p-stacking, C–H· · ·O, C–H· · ·N hydrogen bonds and C–Cl· · ·O halogen bonds determine the supramolecular architecture of these compounds. The crystal packing modes of 1-phenyl and 1-(40- methylphenyl) derivatives are almost identical: there are stacks of molecules additionally strengthened by C–H· · ·N and C–H· · ·O hydrogen bonds, and these stacks are connected into chains by relatively strong, bifurcated C–H· · ·O hydrogen bonds. In 1-(40-chlorophenyl) derivative the strong and linear C–Cl· · ·O halogen bonds together with the C–H· · ·O hydrogen bonds connect the stacks into twodimensional grids. In these three structures there are homogenous stacks: imidazole rings are almost parallel. The heterogeneous stacks (–phenyl/imidazole/phenyl–) are observed in 1-(40-methoxyphenyl)-4-nitro-5-methylimidazole. In this case there are no hydrogen bonds within the stack, there are only interstack interactions. q 2004 Elsevier B.V. All rights reserved.