Polymorphism of an organic system effected by the directionality of hydrogen-bonding Chains

Four polymorphs of 2-[methyl(phenyl)amino]nicotinic acid were discovered, and their single crystal structures were obtained at 90 K. In addition, one monohydrate and one salt were also crystallized and measured. Among the crystal structures, there are 17 crystallographically independent conformations. More interestingly, the four anhydrate forms are tessellated similarly by stacking of one-dimension hydrogen-bonding chains and, yet, the directionalities of the hydrogen-bonding chains are unique in each polymorph.