Benzo-21-Crown-7/Secondary Dialkylammonium Salt [2]Pseudorotaxane- and [2]Rotaxane-Type Threaded Structures

Abstract

We demonstrate that secondary dialkylammonium salts can thread through the cavity of benzo-21-crown-7 to form [2]pseudorotaxanes with binding constants (527-1062 M-1 in acetone) higher than the corresponding values (135-261 M-1 in acetone) of the analogous complexes with their traditionally used host, dibenzo-24-crown-8. Based on this new benzo-21-crown-7/secondary dialkylammonium salt recognition motif, a [2]rotaxane was successfully prepared. The formation of these threaded structures was confirmed by proton NMR spectroscopy, electrospray ionization mass spectrometry, and X-ray single crystal analysis.

The radiolytic behavior and mechanism of calixarene crown ether under γ-irradiation

“…The result implies the ring opening of crown ether structure of BC results in the formation of phenolic hydroxyl groups and unsaturated carbonyl groups. All the chemical shifts in the 1 H NMR are assigned to appropriate H atoms, which is consistent with the reference [33]. Compared with unirradiated BC, no obvious changes in the NMR spectra were observed, implying that the chemical structure of BC is changed slightly when the dose is less than 1400 kGy (The mole ratio of nonvolatile radiolytic products is less than 1% in irradiated BC).…”

A Versatile Axle for the Construction of Disassemblage Rotaxanes

“…In CDCl 3 , the strong ion pairs greatly weakens pseudorotaxane 8 (K A = 17˘0.6 M´1) when compared to the typical association observed in the millimolar range for the complex of DB24C8 with R 2 NH 2 + PF 6´s alts [24][25][26]. Tighter association was observed in DMSO-d 6 (K A = 250˘10 M´1). This value is consistent with literature values [27][28][29].…”

“…Complex formation between pseudorotaxane 8 and the wheel were investigated in various solutions (CDCl 3 , DMSO-d 6 , and 70/30 (v/v) DMSO-d 6 to D 2 O) at 25.0˝C. For the assay performed in CDCl 3 , a constant concentration of pseudorotaxane 8 (10 mM) in 0.5 mL CDCl 3 was exposed to an increasing amount of wheel.…”

“…The rotaxane architecture provides a promising universal framework for sensor development [3][4][5][6][7]. [2]Rotaxanes comprise a circular molecule (wheel) threaded over a linearly shaped molecule (axle) with large groups (blocking groups) attached to the axle's ends to keep the wheel threaded.…”

Recent Advances in the Synthesis of Ammonium-Based Rotaxanes

“…The scope of this reaction has been extended to different components (crown ether and blocking groups) with success. This end-capping reaction has been exploited several times by this group [2][3][4][5][6] and others [7][8][9] to prepare various rotaxane assemblies. Other acylating reagents have been studied to replace anhydrides, which can be incompatible with some functional groups.…”