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

Abstract

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 1H MAS NMR signals. At elevated temperatures, motional averaging of the split 1H 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.