18-Fold interpenetration and concomitant polymorphism in the 2:3 co-crystal of trimesic acid and 1,2-bis(4-pyridyl)ethane

The 2:3 co-crystal of trimesic acid and 1,2-bis(4-pyridyl)ethane (2) exhibits concomitant polymorphism. Form II of 2 is the expected hexagonal (6,3) network, whereas form I is a (10,3)-a network that exhibits an unprecedented 18-fold level of interpenetration.