Persistent CH···π Interactions in Mefenamic Acid Complexes with Cyclic and Acyclic Amines

Interaction of mefenamic acid [2-(2,3-dimethylphenyl)aminobenzoic acid, maH] with piperazine (ppz), 1,4,7,10-tetraazacyclododecane (cyclen), meso-5,7,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (teta), and tris(hydroxymethyl)aminomethane (tris) resulted in crystalline proton-transfer complexes of the compositions (ppzH2)(ma)2·4H2O 1, (cyclenH2)(ma)2·2H2O 2, (tetaH2)(ma)2·2H2O 3, and (trisH)(ma)·H2O 4. Immediate cation−anion hydrogen bonds and those mediated by water molecules are the prime driving forces for the maH and amine assembly. Persistent CH···π interactions involving the aromatic rings were found to play an important role in the formation of final structures. All complexes reveal the pronounced segregation of hydrophilic and hydrophobic regions.