Solvent-Dependent Self-Assembly of a Pillar[5]arene-Based Poly-Pseudo-Rotaxane Linked and Threaded by Silver(I) Trifluoroacetate: A Double Role

Abstract

In the supramolecule area, the fabrication of a new concept called polyrotaxanes or poly-pseudo-rotaxanes remains challenging. We herein report the formation of a poly-pseudo-rotaxane in which the same salt-type guest serves both linking and threading in the resulting structure. The combination of A1/A2-thiopyridyl pillar[5]arene (L) and silver(I) trifluoroacetate in CHCl 3 /CH 3 OH afforded a one-dimensional (1D) poly-pseudo-rotaxane. In this structure, to our surprise, the AgCF 3 CO 2 guest not only links the di-armed L ligands via an infinite −L−Ag−L−Ag− arrangement but also threads into a pillar[5]arene cavity in a dimer form, (AgCF 3 CO 2 ) 2 . In contrast, the same reaction in CH 2 Cl 2 /CH 3 OH yielded a simple 1D coordination polymer because an included CH 2 Cl 2 molecule in the pillar[5]arene cavity prevents the threading of the silver(I) trifluoroacetate guest. Comparative 1 Hand 19 F-NMR studies support the solvent-dependent poly-pseudo-rotaxane formation at a lower concentration of L.

Solvent-Directed Hierarchical Self-Assembly of Tetraphenylpyrazine-Cholesterol with Amplified Circularly Polarized Luminescence

“…Since the solvent has a significant influence on the hierarchically chiral self-assembly of TPP-Chol, other organic solvents were also investigated in detail. ,, After a systematical investigation of TPP-Chol in various solvents, we found that TPP-Chol with the concentration of 5 × 10 –3 mol/L formed a transparent solution in chloroform but viscous solution in hexane, toluene, and p -xylene, and suspension in other solvents including 1,2-dichloroethane (DCE), tetrahydrofuran (THF), ethyl acetate (EA), dodecanol (12-OH), acetone, and methanol, etc. The self-assembly behavior of TPP-Chol in these solvents was further investigated by the CD measurements.…”

“…In artificial self-assembly systems, the chiral molecular building blocks can be collectively driven by the hydrogen-bonding, π–π stacking, metal–ligand coordination and other noncovalent interactions, thereby resulting in various hierarchical chirality expressions for the resultant supramolecular polymers . The expression of hierarchical chirality plays a crucial role in determining the structures of chiral supramolecular materials and endows them with dynamic and smart functions. − The challenge is how to achieve the assembled nanostructures with chirality at different scales through the hierarchical self-assembly, due to the high complexity and tunable mutability affected by solvent, − assembly pathway, and other external stimuli − in solution assembly systems. In the recent years, we have developed a series of cholesterol-based building blocks to construct the metal-organic supramolecular polymers with dynamic supramolecular chirality regulation, including chirality amplification, helix-to-superhelix transformation and handedness inversion .…”