Engineering the solid state with 2-benzimidazolones

Six derivatives of 2-benzimidazolone, disubstituted in the 4 and 5 positions, have been synthesized, and their structures have been determined in the solid state. Four of these compounds crystallize as molecular tapes. Compounds 1-(CH3)2, 1-Cl-2, and 1-Br-2 form tapes that pack with their long axes parallel; compounds 1-H-2 and 2-H-2 form tapes that pack with their long axes at an angle to one another. Compounds 1-F-2 and 1-I-2 crystallize with a three-dimensional network of hydrogen bonds. The packing arrangement of molecular tapes is rationalized on the basis of closest packing and electrostatic interactions between aromatic rings. The occurrence of the network motif rather than the tape motif for 1-F-2 and 1-I-2 is rationalized on the basis of secondary interactions involving the halogen atoms.