Discrete\nStacking of Aromatic Oligoamide Macrocycles

Abstract

Unlike the precise structural control\ntypical of closed assemblies,\ncurbing the stacking of disc- and ring-shaped molecules is quite challenging.\nHere we report the discrete stacking of rigid aromatic oligoamide\nmacrocycles <b>1</b>. With increasing concentration, the aggregation\nof <b>1</b> quickly plateaus, forming a discrete oligomer, as\nsuggested by 1D ¹H, 2D nuclear Overhauser effect, and diffusion-ordered\nNMR spectroscopy. Quantum-chemical calculations indicate that the\ntetramer of <b>1</b> is the most stable among oligomeric stacks.\nX-ray crystallography revealed a tetrameric stack containing identical\nmolecules adopting two different conformations. With a defined length\nand an inner pore capable of accommodating distinctly different guests,\nthe tetramers of <b>1</b> densely pack into 2D layers. Besides\nbeing a rare system of conformation-regulated supramolecular oligomerization,\nthe discrete stacks of <b>1</b>, along with their higher-order\nassemblies, may offer new nanotechnological applications.