Discrete Stacking of Aromatic Oligoamide Macrocycles

Abstract

Unlike the precise structural control typical of closed assemblies, curbing the stacking of disc- and ring-shaped molecules is quite challenging. Here we report the discrete stacking of rigid aromatic oligoamide macrocycles 1. With increasing concentration, the aggregation of 1 quickly plateaus, forming a discrete oligomer, as suggested by 1D (1)H, 2D nuclear Overhauser effect, and diffusion-ordered NMR spectroscopy. Quantum-chemical calculations indicate that the tetramer of 1 is the most stable among oligomeric stacks. X-ray crystallography revealed a tetrameric stack containing identical molecules adopting two different conformations. With a defined length and an inner pore capable of accommodating distinctly different guests, the tetramers of 1 densely pack into 2D layers. Besides being a rare system of conformation-regulated supramolecular oligomerization, the discrete stacks of 1, along with their higher-order assemblies, may offer new nanotechnological applications.

Homochiral [2.2]Paracyclophane Self‐Assembly Promoted by Transannular Hydrogen Bonding

“…Indeed, DOSY NMR measurements in CDCl 3 (Figure 4b)c ould be used to verify supramolecular growth through translational diffusion coefficients (D)obtained at various concentrations and temperatures.For (AE)-1b at 25 8 8C, D (10 À10 m 2 s À1 )d ecreases from 6.7 AE 0.1 at 1mm,t o5.5 AE 0.1 at 15 mm,t o5.1 AE 0.1 at 30 mm.T he latter value expectedly decreases further (to 2.7 AE 0.1) upon lowering the temperature to À10 8 8C. [28] Thec hanges observed in relative volume, V 1b /V TMS ,u pon variation of concentration and temperature [36 AE 2( 1mm,2 58 8C), 50 AE 2 (15 mm,2 5 8 8C), 56 AE 2( 30 mm,2 5 8 8C), 112 AE 9( 30 mm, À10 8 8C)],a re consistent with pCp self-association and the trends discussed above. [28] Thec hanges observed in relative volume, V 1b /V TMS ,u pon variation of concentration and temperature [36 AE 2( 1mm,2 58 8C), 50 AE 2 (15 mm,2 5 8 8C), 56 AE 2( 30 mm,2 5 8 8C), 112 AE 9( 30 mm, À10 8 8C)],a re consistent with pCp self-association and the trends discussed above.…”

Macrocyclization Reactions: The Importance of Conformational, Configurational, and Template-Induced Preorganization

“…This kind of [1 + 1] macrocyclization approach has been shown to be also effective for the preparation of some macrocycles with highly constrained backbones. 260,261,264 In some instances (synthesis of 232a), the poor solubility of the intermediates precluded use of this general methodology, and it was necessary to perform the coupling of the pentameric diamines 230 and the monomeric diacid 231a (method B in Figure 66). The corresponding hexameric macrocycles 232 were obtained in 46−70% yields ( Figure 66).…”

Homochiral [2.2]Paracyclophane Self‐Assembly Promoted by Transannular Hydrogen Bonding

“…The latter value expectedly decreases further (to 2.7±0.1) upon lowering the temperature to −10 °C. The trends, consistent with pCp self‐assembly, are alternatively expressed through estimated hydrodynamic volumes relative to a non‐aggregating internal reference tetramethylsilane (TMS) . The changes observed in relative volume, V 1 b / V TMS , upon variation of concentration and temperature [36±2 (1 m m , 25 °C), 50±2 (15 m m , 25 °C), 56±2 (30 m m , 25 °C), 112±9 (30 m m , −10 °C)], are consistent with pCp self‐association and the trends discussed above.…”