Unsymmetric Bistable [c2]Daisy Chain Rotaxanes which Combine Two Types of Electroactive Stoppers

Abstract

Mechanically interlocked molecules (MIMs) have emerged as intriguing building blocks for the construction of stimuli‐responsive devices and materials. A particularly interesting and well‐implemented subclass of MIMs is composed of symmetric bistable [c2]daisy chain rotaxanes. Topologically, they consist in the double thread of two symmetric macrocycles that are covalently linked to an axle bearing two switchable stations and a bulky stopper to avoid unthreading. Herein we report the synthesis and characterization of a series of unsymmetric bistable [c2]daisy chain rotaxanes that present two different electroactive units as stoppers (an electron donor triarylamine and an electron acceptor perylene bisimide unit). Using a combination of 1D and 2D NMR along with cyclic voltammetry, we demonstrate that the pH actuation of the mechanical bond can be used to modulate the electrochemical properties of the bistable [c2]daisy chain rotaxanes when switching between the contracted and extended forms.

Design of Collective Motions from Synthetic Molecular Switches, Rotors, and Motors

“…This strategy to obtain pH-switchable daisy chains has since been reported in the preparation of other [c2]daisy chains, 985 including unsymmetric ones. 986 In addition, various research groups developed new [c2]daisy chains for which the linear contraction/extension can be triggered by different stimuli such as light, 987 solvent polarity, 988 or even electric field. 989 Very recently, the group of Chiu showed the possibility to access daisy chains of higher order (namely [c3] and [c4]) that are able to contract and extend in the 2D and 3D spaces (Figure 79b).…”

Daisy chain architectures: from discrete molecular entities to polymer materials

“…However, some groups reported the use of molecular [c2]daisy chain architectures as sensors for various physical and chemical effectors. 33,49,50 In 2014, Yang and coworkers reported a fluorescent sensor based on a pillararene modified with an anthracene moiety (entry 8, Table 1). In moderately polar solvents such as chloroform, the pillararene derivative tends to form a [c2]daisy chain architecture which displays a strong fluorescence at B420 nm, due to limited motions of the anthracene moieties.…”

“…In 2019, our group reported the synthesis of the first and so far unique example of unsymmetric bistable [ c 2]daisy chain rotaxane (compound 1 , Scheme 1). 33 The design consisted in a pH-sensitive [ c 2]daisy chain blocked on one extremity by a triarylamine unit as electron donor and on the other extremity by a perylene acceptor. In order to reach the expected unsymmetric compound from the symmetric pseudo-[ c 2]daisy chain, the sequential approach was preferred over the one-pot procedure, as purification procedures were easier.…”

Active Metal Template Synthesis and Characterization of a Nanohoop [c2]Daisy Chain Rotaxane

“…Thus, when viewed as components for investigating nanoscale motion through macroscopic actuation, these structures represent especially fascinating targets. To date, a majority of the reported daisy chain architectures are actuated through light, pH, electrochemical, and metal‐coordination‐based mechanisms, with thermally actuated systems being relatively rare . This likely stems from the typical method of preparation, in which interactions such as metal‐coordination and radical–radical pairing template the formation of the desired daisy chain .…”