Directionality and site selectivity of N⋯Cl halogen bonding in two azaaromatic chloride crystals

Two azaaromatic chlorides of bis-2,4-[(2-formoyl)phenoxyl]-6-chloro-[1,3,5]triazine (1) and bis-2,4-(4-carbomethoxyphenoxyl)-6-chloro-[1,3,5]triazine (2) have been synthesized and structurally characterized. The crystal structures of 1 and 2 reveal unusually short intermolecular N⋯Cl distance of 3.095(2) and 3.088(3) Å, meaning the formation of strong halogen bonding. The strengths of the intermolecular N⋯Cl halogen bonding and the molecular electrostatic potentials in these crystal structures have been calculated by Density Functional Theory Calculations. The capacities of the N⋯Cl halogen bonding, lone pair⋯π interaction, π–π stack and C−H⋯O hydrogen bonding in the directionality of supramolecular self-assembly have been analyzed by structural study and theoretical calculations. The site selectivity of the N⋯Cl halogen bonding is illustrated by the difference of electrostatic potential of the N atoms on the molecule.