Strong Aggregation and Directional Assembly of Aromatic Oligoamide Macrocycles

Abstract

Aromatic oligoamide macrocycles exhibit strong preference for highly directional association. Aggregation happens in both nonpolar and polar solvents but is weakened as solvent polarity increases. The strong, directional assembly is rationalized by the cooperative action of dipole-dipole and π-π stacking interactions, leading to long nanotubular assemblies that are confirmed by SEM, TEM, AFM, and XRD. The persistent nanotubular assemblies contain non-collapsible hydrophilic internal pores that mediate highly efficient ion transport observed with these macrocycles and serve as cylindrical sites for accommodating guests such as metal ions.

Two‐Component Supramolecular Gels Derived from Amphiphilic Shape‐Persistent Cyclo[6]aramides for Specific Recognition of Native Arginine

“…The reflection around 0.37 nm was attributed to resulting from the corresponding p-p stacking interactions between the coplanar aromatic backbones (2q, 20-308). [21,31] Similar results were obtained for 1·TEA-HCl ( Figure S13). Thus, the information retrieved from the wide-angle X-ray diffraction analysis supports the stacking of the macrocyclic molecules into nanotubular structures, which is consistent with the observation of very long fibers from SEM and TEM images.…”

“…[20] With their shape-persistent aromatic surfaces, the macrocycles carrying extra-annular alkyl side chains are prone to self-aggregation in both polar and nonpolar solvents as a consequence of the cooperative action of dipole-dipole and p-p stacking interactions. [21] With their correctly arranged amide oxygen atoms pointing inwards, the near-planar six-residue macrocycles, [22] dubbed cyclo [6]aramides, have shown highly selective recognition of guanidinium ions, [23] efficient separation of metal ions, [24] and a high affinity for dialkylammonium salts. [25] Remarkably, a cyclo [16]aramide with a larger nanosized cavity could accommodate even a depsipeptide antibiotic valinomycin.…”

Macrocyclic shape-persistency of cyclo[6]aramide results in enhanced multipoint recognition for the highly efficient template-directed synthesis of rotaxanes

“…In the case of macrocycle 1 , which is decorated peripherally with sterically crowded alkyl groups, the reaction offers [3]rotaxane [3]CR-C 16 as the sole product in a yield of 86%. Using macrocycle 2 , which tends to severely aggregate in solution due to the presence of linear alkyl chains, 28 the yield of [3]rotaxane [3]CR-C 12 was increased up to 91%. To the best of our knowledge, this is one of the rare examples of the synthesis of [3]rotaxanes in excellent yields reported hitherto using a non-metal coordination strategy.…”

Structural analysis of bis-bispidine tetraazamacrocycle: Long-range weak interactions in a channeled organic crystal

“…Synthesis of 9,9,18,18-tetraethoxy-3,6,12,15-tetraazapentacyclo[13.3.1.1 3,17 .1 6,10 .1 8,12 ] docosane (2) Tetraethoxy bis-bispidine 2 was synthesized according to a modified literature procedure [21]. To a suspension of bisamide 6 (0.192 g, 0.377 mmol) in anhydrous diethyl ether (6.6 mL) at ambient temperature under N 2 was added dropwise DIBALH (1.98 mL of a 1.0 M solution in toluene, 1.98 mmol).…”

“…A feasible strategy to align macrocycles involves the utilization of directional interactions such as hydrogen bonding, p-stacking, and dipole-dipole interactions. This has led to the assembly of tubular structures from building blocks containing aromatic [7][8][9][10], peptide [11,12], urea [13,14], and oligosaccharide units [15]. However, weak directional interactions such as CAHÁ Á ÁO hydrogen bonds have rarely been reported as the principal driving forces in the formation of channeled organic crystals [16].…”