The master of chemical topology

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

“…On mixing A, B,a nd C,s ome supramolecular arrangements were formed preferentially from among the multiple different possible ones. Ammonium-containing hermaphroditem olecule C selectively assembled into an interwoven [c2]daisy chain G,r ather than being encircled by either af ree DB24C8 or another substituted macrocycle C to give [2]rotaxane species D or E.S imilarly,h ermaphrodite molecule C didn ot threada nilinium-containing axle A to give F in ap reponderant fashion. On one hand, these results arise from the much greatera ffinity of the DB24C8f or the benzylammonium moiety than for the anilinium one.…”

“…On one hand, these results arise from the much greatera ffinity of the DB24C8f or the benzylammonium moiety than for the anilinium one. On the other hand, the possibilityt oa chieve two binding sites between the templates and the macrocycles in as ingle molecule (i.e.,t he [c2]daisyc hain) is favored in term of enthalpy with respectt o the formation of single [2]rotaxanes in which interaction takes place at only one site. As ar esult, hermaphrodite molecule C could be entirely converted into [c2]daisy arrangement G, whereas excess DB24C8 B threaded chemical axle A quantitatively to give semi-rotaxane H.T he subsequent chemical connectiona fforded tetra-interlocked architecture I and allowed for the incorporation of an extra unoccupied molecular station.…”

“…In the rotaxane series, doubly interlocked rotaxanes (i.e.,[ c2]daisy chain [1] ) attractedc hemists because of their peculiar interwoven architecture. In 2000, J.-P.S auvage [2] was the first to report the synthesis of am etal-based doubly interlocked rotaxanet hat was able to act as as timulus-responsive molecular machine. [3] This novel molecular machine was termeda"molecular muscle" [4] by the author,i nr eference to thec ontractile motion that occurs in human muscles.…”

“…Herein, we report on the synthesis and study of an appealingp H-sensitive tetra-interlocked molecular machine I (Figure 2b). The molecular architecture consists of a[ c2]daisy chain scaffold that is linked to two [2]rotaxane units. The molecular machinery,w hich is inherentt o this hetero [4]rotaxane architecture, should allow for different possible co-conformational states (I, J,a nd K)t hat are ac onsequenceo ft he gliding of the different interlocked components with respect to each other.…”

De catenanos y rotaxanos a interruptores, sensores y coches moleculares

“…En ese entonces Stoddart trabajaba en cómo inactivar uno de los productos que se producían, un herbicida cuyo uso está actualmente prohibido en muchas partes del mundo: el paraquat 6 . Este compuesto es una doble piridina covalentemente unida en posición para que posee ambos nitrógenos cuaternarios metilados y por lo tanto electropositivos.…”