Influence of the Aliphatic Wrapping in the Crystal Structure of Benzene Tricarboxamide Supramolecular Polymers

The syntheses and crystal structures of two novel trisamides, the ethyl-(2) and propyl-substituted (3) N,N',N ''-trialkylbenzene-1,3,5-carboxamides, are reported. The Compounds ire prepared in good yields by aminolysis of the trimethyl-1,3,5-benzenecarboxy late and the respective primary amine. Compound 2 crystallizes in the P2(1)2(1)2(1) space group with a complete molecule in the asymmetric unit and four molecules per unit Cell, whereas 3 does it in the R3c space group with one-third of the molecule in the asymmetric unit and six molecules per unit cell. Their solid-state structures show that the N-H center dot center dot center dot O=C hydrogen bond plays the most important role in the supramolecular framework of both cases, despite considerable differences in crystal packing. Supramolecular sheets are formed in 2, whereas molecules of 3 are packed in a H-bonded primitive cubic [4 6] three-dimensional network. The main difference in the molecular conformation is the tilting of the carboxamide group with respect to the aryl, which in the case of 3 occurs in the same direction, leading to the formation of "solid-state" chiral molecules.