The impact of the amide connectivity on the assembly and dynamics of benzene-1,3,5-tricarboxamides in the solid state

Solid-state NMR experiments as well as extensive Car-Parrinello Molecular Dynamics simulations are used to study the dependence of supramolecular self-organization of benzene-1,3,5-tricarboxamides (BTA) on the local orientation of the amide functionality. Unlike the known symmetric co-planar helical arrangement of CO-centered BTAs found in supramolecular architectures like supramolecular polymers in gels, N-centered BTAs adopt an asymmetric helical arrangement in the solid-state. The resulting tilt angle between the aromatic cores of neighboring BTA molecules leads to a breaking of the three-fold molecular symmetry and thus causes a splitting of H-1 MAS NMR signals. At elevated temperatures, motional averaging of the split H-1 MAS NMR signals is observed, which can be attributed to certain dynamics on the ms time scale of individual BTA molecules in the columnar packing arrangement.