Guest-Induced Isomerization of Net and Polymorphism in Trimesic Acid–Arylamine Complexes

Two molecular complexes of 1,3,5-benzenetricarboxylic acid (BTA) with 4,4′-methylenebis(2,6-dimethylaniline) (MBDA) and 2,6-dimethylaniline (DMA) led to the formation of two host guest systems. The MBDA species get trapped in hexagonal channels produced within the crystal lattice of the BTA. On the other hand, the DMA guest moieties are encapsulated into the channel formed by the brick wall network of BTA and water molecules. Isomerization of the (6,3) net, from hexagonal to brick wall, occurs due to the extra flexibility in the cluster of DMA guests which led to the additional hydrogen bonds with the host framework and incorporation of water molecules into the net. Each system contains two BTA species in the asymmetric unit with different ionic states, indicating that the proton transfer depends also upon the solid state environment. Crystallization of the BTA and MBDA mixture with different concentrations produces solvates of BTA–MBDA complex and MBDA crystallizes out in two forms depending upon the BTA/MBDA ratio used in the solution. The methanol solvate of the complex is dimorphic and one form is isostructural to the ethanol solvate.