Structures of hydro-, chloro-, and bromo-substituted maleimides and 2,6-diaminopyridines, and of some of their 1 : 1 heterodimers

The crystal structures of a series of 3,4-diX-substituted maleimides and 3,5-diY-substituted-2,6-diaminopyridines (X, Y = H, Cl, Br) have been determined. Some of their hydrogen-bonded 1:1 heterodimers have also been synthesized and their crystal structures studied to investigate the influence of halogens on the crystal packing and to determine a possible role for halogen bonding. Single-crystal X-ray analysis of the crystals of the heterodimers revealed that the expected triple H-bonded structures were formed. This crystal engineering exercise has been partially successful, giving six mixed hydrogen- and (when possible) halogen-bonded compounds whose structures were found to be dependent on the nature and the position of the halogen substituents.