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. 2021 Jan 14;11(5):2995-3002.
doi: 10.1039/d1ra00078k. eCollection 2021 Jan 11.

Concentration-dependent supramolecular self-assembly of A1/A2-asymmetric-difunctionalized pillar[5]arene

Talal F Al-Azemi  1 , Mickey Vinodh  1
Affiliations

Concentration-dependent supramolecular self-assembly of A1/A2-asymmetric-difunctionalized pillar[5]arene

Talal F Al-Azemi et al. RSC Adv. .

Abstract

A series of A1/A2-bromoalkoxy-and-hydroxy-difunctionalized pillar[5]arenes were synthesized by the removal of the pillar[5]arene-bearing benzyl group using catalytic hydrogenation. The difunctionalized pillar[5]arene bearing 8-bromooctoxy and benzyloxy substituents at the A1/A2 positions formed pseudo[1]rotaxane at low concentration and double-threaded supramolecular dimer at high concentration. The supramolecular self-assembly behavior has been probed with multiple methods including varying (variable) concentration 1H NMR spectroscopy, diffusion-ordered spectroscopy (DOSY), dynamic light scattering (DLS) measurements, isothermal titration calorimetry (ITC), and single-crystal X-ray analysis.

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Conflict of interest statement

There are no conflicts to declare.

Figures

Scheme 1
Scheme 1. Synthesis of A1/A2 difunctionalized bromo-hydroxy pillar[5]arenes.
Fig. 1
Fig. 1. Partial 1H NMR spectra (600 MHz, CDCl3) of Pillar-1c at 298 K (a) and 233 K (b).
Fig. 2
Fig. 2. Partial 1H NMR spectra of pillararene aromatic frame (600 MHz, CDCl3, 298 K) of Pillar-1c at 4 mM (a) and 50 mM (b).
Fig. 3
Fig. 3. Hydrodynamic radii distributions of Pillar-1c in chloroform at two different concentrations (2, and 50 mM).
Fig. 4
Fig. 4. ITC dilution raw heats for sequential injection in chloroform at 298 K for 2 (red) and 50 (black) mM of Pillar-1c (a), and the integrated heat data for Pillar-1c at 50 mM fitted to a dimer dissociation model (b).
Fig. 5
Fig. 5. Supramolecular double-threaded dimer of Pillar-1c. (a) The top view, and (b) the side view. Red, grey (or green) and yellow denote oxygen, carbon and bromine, respectively. Hydrogen atoms are omitted for clarity.
See this image and copyright information in PMC

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