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.
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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.
Perspectives
Our study shed light, at the atomistic scale level, on the reason why the disassembling process in the two rotaxanes is different. The elliptic shape of the opening of the ring is capable of recognizing two different configurations of the terminal azobenzene group of the axle in the dethreading process. This insight may open the way to the construction of light-powered molecular pumps.
Gloria Tabacchi
university of insubria
Read the Original
This page is a summary of: Dethreading of a Photoactive Azobenzene-Containing Molecular Axle from a Crown Ether Ring: A Computational Investigation, ChemPhysChem, March 2016, Wiley,
DOI: 10.1002/cphc.201501160.
You can read the full text:
Resources
Disassembling of a rotaxane
Movie showing the disassembling process of a rotaxane. The process consists in the dethreading of the ZZ-axle from the ring.
Disassembling of a pseudorotaxane
Movie showing the dethreading of a EE-axle from the ring. No intermediates and transition states are detected in the process
Additional Information for article http://dx.doi.org/10.1002/cphc.201501160
1)Supplementary data for this article. 2) All the figures and schemes of the original paper (high-resolution) . 3)Graphical abstract depicting the energy profile of the dethreading of the ZZ-axle.
ResearchGate
Our article page in ResearchGate
Academia.edu
Our article page in Academia
Molecular Machine (Wikipedia)
To place our reseach in a broader context, here is a Wikipedia article on Molecular Machine mentioning the need of accurate theoretical models for further advance in the field. Our paper is referred to.
Blog post
This blog post provides a quick and easy description of this research using figures and movies.
ChemPhysChem special issue on Molecular Machines
Link to the special issue of ChemPhysChem on molecular machines, in which our paper is included. The issue contains many other very interesting contributions to this exciting field.
Open Access
Green open access version of this article
Contributors
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