Synthesis of a pH‐Sensitive Hetero[4]Rotaxane Molecular Machine that Combines [c2]Daisy and [2]Rotaxane Arrangements

Abstract

The synthesis of a novel pH-sensitive hetero[4]rotaxane molecular machine through a self-sorting strategy is reported. The original tetra-interlocked molecular architecture combines a [c2]daisy chain scaffold linked to two [2]rotaxane units. Actuation of the system through pH variation is possible thanks to the specific interactions of the dibenzo-24-crown-8 (DB24C8) macrocycles for ammonium, anilinium, and triazolium molecular stations. Selective deprotonation of the anilinium moieties triggers shuttling of the unsubstituted DB24C8 along the [2]rotaxane units.

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).…”

Thermodynamic Insights on a Bistable Acid–Base Switchable Molecular Shuttle with Strongly Shifted Co‐conformational Equilibria

“…The energy‐level diagram shown in Figure is also interesting because it clearly shows that the acid strength of the pH‐switchable site is affected by the position of the ring. Previous experiments indicate that deprotonation of the ammonium unit is extremely difficult to achieve in the absence of an alternative station for the crown ether macrocycle . The data collected on the present rotaxane show that the acidity of its ammonium unit changes by at least 7.6 p K a units upon switching the ring position.…”

Distinguishing Two Ammonium and Triazolium Sites of Interaction in a Three‐Station [2]Rotaxane Molecular Shuttle

“…The targeted interlocked molecule 7 (Scheme 1) was synthesized from the previouslys ynthesized aniliniuma lkyne axle 1, [13] the azidocarbamate 3, [13] and the commercially available DB24C8 by following af our-step synthetic sequence. The semirotaxane 2 was obtained easily and quantitatively from the anilinium-containing axle 1 by using at hree-fold excesso f DB24C8 in the hydrogen-bond-promoting solventd ichloromethane.I tw as then directly subjected to ac opper(I)-catalysed Huisgen [14] alkyne-azide 1,3-dipolar cycloaddition [15] by using the azido compound 3 in the presence of copperh exafluorophosphate and 2,6-lutidine.…”