Molecular machines in action
What is it about?
Rotaxanes are made by a ring-type molecule and an axle-type molecule bearing bulky groups (stoppers) at both extremities, so that the molecular ring and axle components are mechanically interlocked. These species are interesting for the construction of molecular machines, because the interaction between the components can be modulated by external signals, e.g. light. In this way, stimuli-controlled movements of the molecular components can be achieved. However, how an axle exits from a ring (dethreading process) is still an open question at molecular level. For this reason, we modeled the dethreading of rotaxanes formed by a dialkylammonium axle and a crown ether ring. Our results explain the reasons for the significant differences in the thermodynamic and kinetic behaviour of two rotaxanes which govern the functionality of such light-powered molecular devices.
Why is it important?
For the first time, we elucidate the interactions between the molecular components which control the dethreading process at the molecular level. Different escape mechanisms are revealed for two different configurations of the axle: while the former undergoes a one-step process, the dethreading of the latter proceeds through a transition state and an intermediate structure.
The following have contributed to this page: Gloria Tabacchi
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