Crystal engineering with hydrogen bonds and halogen bonds

Molecular tapes mediated via strong O-H center dot center dot center dot N hydrogen bonds and weak C-I center dot center dot center dot O interactions are present in complexes of 4-nitrobenzoic acid center dot 4-iodopyridine and 3,5-dinitrobenzoic acid center dot 4-iodopyridine. Crystal structure of 4- nitrobenzamide center dot 4-iodobenzamide has amide dimer tape and iodo center dot center dot center dot 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 center dot center dot center dot nitro heterosynthons may be simultaneously exploited for crystal design.