Thermoresponsive Shuttling of Rotaxane Containing Trichloroacetate Ion

Abstract

A thermoresponsive rotaxane shuttling system was developed with a trichloroacetate counteranion of an ammonium/crown ether-type rotaxane. Chemoselective thermal decomposition of the ammonium trichloroacetate moiety on the rotaxane yielded the corresponding nonionic rotaxane accompanied by a positional change of the crown ether on the axle. The rotaxane skeleton facilitated effective dissociation of the acid, markedly lowering the thermal decomposition temperature.

Complexation Between (O‐Methyl)6‐2,6‐Helic[6]arene and Tertiary Ammonium Salts: Acid/Base‐ or Chloride‐Ion‐Responsive Host–Guest Systems and Synthesis of [2]Rotaxane

“…For stimuli‐responsive host–guest complexation purposes, crown ethers, cucurbiturils, cyclophanes, cyclic lactams, and others have been utilized as synthetic hosts, and protonated organic bases including secondary ammonium, pyridinium, benzimidazolium, and other protonated salts were usually used as the guests. Tertiary amines are also an important kind of organic base, however, few examples of protonated tertiary ammonium salts as guests for responsive host–guest complexation were hitherto reported …”

“…For stimuli-responsive host-guest complexation purposes,c rown ethers, [5] cucurbiturils, [6] cyclophanes, [7] cyclic lactams, [8] and others [9] have been utilized ass ynthetic hosts, and protonated organic bases including secondary ammonium, [10] pyridinium, [11] benzimidazolium, [12] and other protonated salts [13] were usually used as the guests.T ertiary amines are also an important kind of organic base, however,few examples of protonated tertiary ammonium salts as guests for responsive host-guest complexation were hitherto reported. [14] Macrocyclic arenesi ncludingc alixarenes, [15] resorcinarene, [16] cyclotriveratrylene, [17] pillararenes, [18] and their analogues [19] have become one of the most studied synthetic macrocyclic hosts in recent decades. It is known that pillararenes can form complexes with quaternary ammonium saltsm ainly by cati-on···p interactions, [20] and calix [6]arene derivatives can complex with secondary ammonium salts.…”

Supramolecular polymerization of a ureidopyrimidinone‐based [2]catenane prepared via ring‐closing metathesis

“…Mechanically interlocked molecules are prime components of molecular machines and have found applications in molecular switches,6 coatings,7 and electronics 8. The RCM‐assisted introduction of mechanical bonds in defined molecular systems has expanded the field toward interlocked polymeric systems, such as polycatenanes9 and polyrotaxanes 10.…”

Solid-state Rotaxane Switch: Synthesis of Thermoresponsive Rotaxane Shuttle Utilizing a Thermally Decomposable Acid

“…13 Trichloroacetic acid (TCA) thermally decomposes at 167°C to chloroform and carbon dioxide, 13 whereas the decomposition is accelerated in the presence of a suitable amine base. One of the most important points of this system is that it accumulates no salt by the repeated switching, although the stimuli involve simple acidbase reactions, because of the TCA's decomposition to volatile materials.…”

“…13 Therefore, it is conceivable that the formation of tert-ammonium structure and the encapsulated ammonium structure of the rotaxane can be approved, if the decomposition of TCA of the rotaxanes obtained in the solid state progresses at the same temperature as those of the rotaxanes obtained in the solution state. In other words, the expected result should suggest that a similar positional switching in solid state to that in solution state occurs.…”