A Strategy Utilizing a Recyclable Macrocycle Transporter for the Efficient Synthesis of a Triazolium‐Based [2]Rotaxane

Abstract

A general synthesis of triazolium-containing [2]rotaxanes, which could not be accessed by other methods, is reported. It is based on a sequential strategy starting from a well-designed macrocycle transporter which contains a template for dibenzo-24-crown-8 and a N-hydroxysuccinimide (NHS) moiety. The sequence is: 1) synthesis by slippage of a [2]rotaxane building-block; 2) its elongation at its NHS end; 3) the delivery of the macrocycle to the elongated part of the axle by an induced translational motion; 4) the contraction process to yield the targeted [2]rotaxane and recycle the initial transporter.

Photoinduced Electron Transfer Involving a Naphthalimide Chromophore in Switchable and Flexible [2]Rotaxanes

“…Rotaxanes based on a DB24C8 macrocycle surrounding an axle composed of a dialkyl‐ammonium (amH + ) and a triazolium (tria + ) station have recently been proposed as acid‐base switchable molecular devices . These rotaxanes can be readily synthesized and easily functionalized either at the ring or at the axle.…”

“…Rotaxanes based on aD B24C8 macrocycle surrounding an axle composed of ad ialkyl-ammonium (amH + )a nd at riazolium (tria + )s tation have recently been proposed as acid-base switchable molecular devices. [19][20][21][22][23][24][25][26][27][28][29][30] These rotaxanes can be readily synthesized and easily functionalized either at the ring or at the axle. Hence,w ed esigned a [ 2]rotaxane bearing a phenothiazine (PTZ) donor unit linked to the crown ether ring and ap hotoactivable naphthalimide( NI)a cceptor unit as a stopper( Scheme 1).…”

Active Esters as Pseudostoppers for Slippage Synthesis of [2]Pseudorotaxane Building Blocks: A Straightforward Route to Multi‐Interlocked Molecular Machines

“…The first one consists of the threading and capping of the molecular axle 5 , which contains an ammonium template for DB24C8 and a carboxylic acid that is small enough to allow fast assembly before the axle is stoppered (route 1, Scheme ). The second concerns a slippage strategy from threads 4 a – g ; all contain an active ester of distinct size at the carboxylic side of the axle (route 2, Scheme ).…”

“…By using a diamine, the activated diester‐containing [c2]daisy chain was converted into a unique double‐lasso molecular architecture, also called a cyclic molecular muscle or rotamacrocycle. More recently, we published a route to [1]‐ and [2]rotaxanes, which were devoid of any efficient template, using the well‐known active N ‐hydroxysuccinimide (NHS) ester. In this case, the strategy is based on the use of a recyclable “transporter” of DB24C8, which contains a good ammonium template for the crown ether and a terminal NHS moiety that can be converted into an active ester moiety through the anchoring of a second molecular axle.…”

“…The thermodynamic and kinetic parameters relative to the slipping‐on and off processes are also reported. The further elongation of these building blocks by the addition of an amine that contains a triazolium molecular station or a diamine containing two precursor moieties of triazolium sites is also described. It straightforwardly and efficiently provides a two‐station [2]rotaxane molecular machine and a palindromic two‐station [3]rotaxane molecular machine, respectively.…”