π–π stacking in the polymorphism of 2-(naphthalenylamino)-nicotinic acids and a comparison with their analogues

Four analogs (1–4) of clonixin were synthesized and their polymorphism was studied. Structural similarity was observed between 1 -A and CLX- II , and 3 and CLX- I . π–π stacking played an important role in the hydrate formation of 1 and polymorphism of 2.