Photodriven Clamlike Motion in a [3]Rotaxane with Two [2]Rotaxane Arms Bridged by an Overcrowded Alkene Switch

Abstract

A [3]rotaxane with two [2]rotaxane arms bridged by an overcrowded alkene switch has been constructed to perform the clamlike motion in response to light stimulus. We demonstrated that this [3]rotaxane can undergo reversible conformational changes caused by the trans-cis isomerizations of the central double bond with a favorable photostationary state (up to 90% conversion). It has been shown that the clamlike motion causes remarkable UV-vis and fluorescence spectral changes, allowing it to behave as a reversible optical molecular switch.

Fluorescence Modulation in Tribranched Switchable [4]Rotaxanes

“…As shown in Scheme , the well‐known noncovalent intercomponent interaction between the substituted DB24 C8 ring and the DBA cation was chosen for the mechanical assembly, which has become the basis of many diverse interlocked molecular structures. Among several template‐directed synthetic approaches for the construction of mechanically interlocked rotaxanes, the so‐called threading‐followed‐by‐stoppering protocol17 is one of the most straightforward, especially in systems with the recognition motif provided by DB24 C8/DBA, and the Cu I ‐catalyzed azide–alkyne cycloaddition (CuAAC) reaction7b, 14c, d, 16b was chosen for the stoppering procedure due to its high efficiency and good functional‐group tolerance. A key intermediate in the preparations of [4]rotaxanes 1 and 2 was the trifurcate compound 3 , which has a 1,3,5‐triphenylene core and three arms, each of which incorporates a DBA unit as a primary recognition site for DB24 C8 and a terminal alkyne as a reaction site.…”

Development and advancement of rotaxane dendrimers as switchable macromolecular machines

“…7). 68 The synthesis first involved a bis-crown ether linked with trans-alkene. Two dihydroxyl-functionalized DBA threads were recognized by the crown ether and stoppered by tri-n-butylphosphine-catalyzed esterification.…”

Hetero type III‐B rotaxane dendrimers

“…The most fascinating property of the rotaxane dendrimer is the stimuli-responsive molecular movement within the macromolecules. Several external stimuli have been investigated to trigger the movement of macrocycles in rotaxane, including pH, [11] redox, [12] radiation, [13] temperature, [14] cation/anion, [15] solvent etc., [16] and act as molecular elevator, [17] molecular pump, [18] molecular motor, [19] molecular machine, [20,21] and organocatalyst. [22] The introduction of this switching property into macromolecular rotaxane dendrimers can generate total molecular size changes and could be potentially applied for drug carrier or molecular electronics.…”