Crystal engineering with hydrogen bonds and halogen bonds

Molecular tapes mediated via strong O–H⋯N hydrogen bonds and weak C–I⋯O interactions are present in complexes of 4-nitrobenzoic acid·4-iodopyridine and 3,5-dinitrobenzoic acid·4-iodopyridine. Crystal structure of 4-nitrobenzamide·4-iodobenzamide has amide dimer tape and iodo⋯nitro interaction in orthogonal directions. There is good structural insulation in the hydrogen bonding and halogen bonding domains in these crystal structures. However, the less polarizable bromine and chlorine atoms show cross-pairing interactions that are less predictable. These preliminary results show that both carboxylic acid⋯pyridine and iodo⋯nitro heterosynthons may be simultaneously exploited for crystal design.