Autonomous shuttling driven by an oscillating reaction : proof of principle in a cucurbit[7]uril bodipy pseudorotaxane

Abstract

Miniaturization is a fundamental part of modern technology. Therefore, designing macroscopic machines at molecular level becomes important in terms of mimicking the nature. Despite the numerous molecular machines that were reported in the literature, coupling this design with oscillating reactions to achieve autonomous shuttling was not tried previously. In this thesis, we proposed a novel design for this purpose. Initiating molecular shuttling by oscillating reactions and controlling this shuttling were successfully achieved through a rational design.Oscillating reactions intrigued chemists for a long time, in this work; we propose to utilize oscillations in pH to move the two components of a pseudorotaxane in relation to each other. In a well behaved oscillatory system, the shuttling could be sustained as long as the oscillations continue. This is the first demonstration of a molecular shuttle system in which the ?mobile? component is moving from one station to another in an autonomous fashion. This kind of chemical coupling of an energetically favorable reaction to molecular motion is reminiscent of many biological analogs and therefore highly exciting. Bipyridinium dication substituted BODIPY fluorophore, with a terminal carboxylic acid provides two alternative stations for cucurbit[7]uril (CB7). Changing pH from basic to acidic media results a shuttling of CB7 from one station to another. In addition, the shuttling is accompanied by a change in the emissive properties of the BODIPY dye, which is only observed in the presence of CB7. More striking, it is a demonstration of autonomous shuttling of the pseudorotoxane system in an oscillating pH system.