Enforced Tubular Assembly of Electronically Different Hexakis(m-Phenylene Ethynylene) Macrocycles: Persistent Columnar Stacking Driven by Multiple Hydrogen-Bonding Interactions

Abstract

Hexakis(m-phenylene ethynylene) (m-PE) macrocycles 1-4, sharing the same hydrogen-bonding side chains but having backbones of different electronic properties, are designed to probe the effectiveness of multiple H-bonding interactions in enforcing columnar assemblies. H NMR, absorption, fluorescence, and circular dichroism (CD) spectroscopy indicate that, compared with analogous macrocycles that self-associate based on aromatic stacking which is highly sensitive to the electronic nature of the macrocyclic backbones, macrocycles 1-4 all exhibit strong aggregation down to the micromolar (μM) concentrations in nonpolar solvents. Increasing solvent polarity quickly weakens aggregation. In THF and DMF, the macrocycles exist as free molecules. The observed solvent effects, along with the behavior of 5-F that cannot self-associate via H-bonding, confirm that H-bonding plays the dominating role in driving the self-association of 1-4. The backbone electronic nature does not change the self-assembling pattern common to 1-4. Fluorescence and CD spectra confirm that macrocycles 1-4 assemble anisotropically, forming helical stacks in which adjacent molecules undergo relative rotation to place individual benzene residues in the favorable offset fashion. Columnar alignment of 1-4 is confirmed by atomic force microscopy (AFM), which resolves single tubes consisting of stacked macrocycles. In addition, macrocycles with backbones of different electronic properties are found to undergo heteroassociation, forming hybrid nanotubes. This study has demonstrated the generality of enforcing the alignment of shape-persistent macrocycles, which represents an invaluable addition to the small number of known tubular stacks capable of accommodating structurally varied molecular components and provides self-assembling nanotubes with inner pores allowing ready structural and functional modification.

A macrocyclic oligofuran: synthesis, solid state structure and electronic properties

“…Introduction p-Conjugated macrocycles with well-dened diameters have received signicant attention in the last few decades, mainly because of their unique optical and electronic properties, their host-guest capabilities, and their potential as building blocks for supramolecular materials. [1][2][3][4][5][6] Many p-conjugated macrocyclic systems aggregate into columnar structures, 4,7-11 producing molecular channels that, with the appropriate inner-core functionalization, may give rise to ion channels, rod-like micellar aggregates, and even reaction chambers. [12][13][14][15] A particularly intriguing class of p-conjugated macrocycles is macrocyclic oligothiophenes (C-nT, Chart 1), introduced by Bäuerle's group in sizes ranging from C-8T to C-35T.…”

Equilibration of Imine‐Linked Polymers to Hexagonal Macrocycles Driven by Self‐Assembly

“…Here we access discrete hexagonal imine-linked macrocycles by condensing atruncated analogueof1,3,5-tris(4-aminophenyl)benzene( TAPB) with terephthaldehyde (PDA). [12] The solid-state ordering of shape-persistent macrocycles mimics that of 2D covalent organic frameworks (COFs), whicha re extended, periodics tructures with permanent porositya nd high internal surface areas. The high selectivity for hexagonal macrocycles is enforcedb y their aggregation and crystallization into layered structures with more sluggish imine exchange.…”

“…[8,9] The rigidity and planarity of macrocycles lead to assemblies such as 2D networks, [10] liquid crystals, [11] or nanotubes with well-defined channels. [12] The solid-state ordering of shape-persistent macrocycles mimics that of 2D covalent organic frameworks (COFs), whicha re extended, periodics tructures with permanent porositya nd high internal surface areas. [13][14][15] Macrocycle assemblies confer many of the same de-sirable features as COFs and offer superior processability and greater potential for stimuli-responsive functions.Macrocycle formation and assembly can also provide insight into the analogous processesi nvolved in 2D COF formation, which are poorly understood and uncontrolled.…”

Aggregation and Tunable Color Emission Behaviors of l‐Glutamine‐Derived Platinum(II) Bipyridine Complexes by Hydrogen‐Bonding, π–π Stacking and Metal–Metal Interactions

“…In general, these functional materials could be constructed in a delicately controlled manner through intermolecular interactions such as van der Waals forces, hydrogen‐bonding, electrostatic, and π–π stacking interactions ,–. For example, supramolecular chirality was achieved by controlling the molecular aggregation through hydrogen‐bonding and π–π stacking interactions . Very recently, hexakis( m ‐phenylene ethynylene) macrocycles were reported and showed different columnar assembly with distinct properties driven by multiple hydrogen‐bonding interactions depending on the polarity of the solvents .…”

“…For example, supramolecular chirality was achieved by controlling the molecular aggregation through hydrogen‐bonding and π–π stacking interactions . Very recently, hexakis( m ‐phenylene ethynylene) macrocycles were reported and showed different columnar assembly with distinct properties driven by multiple hydrogen‐bonding interactions depending on the polarity of the solvents . More importantly, the supramolecular materials could be considered as smart materials because the weak intermolecular interactions can be easily disrupted by various stimuli such as temperature, pH, solvents, chemicals, and so forth …”