Polymorphic and Isomorphic Cocrystals of a N-Salicylidene-3-aminopyridine with Dicarboxylic Acids: Tuning of Solid-State Photo- and Thermochromism

The crystal structures and optical properties of (E)-2-methoxy-6-(pyridin-3-yliminomethyl)phenol (1), a N-salicylidene-3-aminopyridine, and its 2:1 dimorphic cocrystals with fumaric acid (2 and 3) and succinic acid (4 and 5) were studied at solid state in order to understand the effects of cocrystallization and molecular packing on their photo- and thermochromic behavior. New criteria for prediction of the chromic properties, based on the rationalization of the intermolecular interaction in the crystal, are also proposed. These results confirm once more the influence of the molecular packing on the chromic properties of solids and extend it to polymorphic and isomorphic cocrystals.