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Dethreading of a Photoactive Azobenzene‐Containing Molecular Axle from a Crown Ether Ring: A Computational Investigation
Author(s) -
Tabacchi Gloria,
Silvi Serena,
Venturi Margherita,
Credi Alberto,
Fois Ettore
Publication year - 2016
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201501160
Subject(s) - azobenzene , axle , rotaxane , metadynamics , crown ether , molecular machine , ring (chemistry) , chemistry , materials science , molecular dynamics , computational chemistry , chemical physics , crystallography , molecule , supramolecular chemistry , nanotechnology , physics , thermodynamics , organic chemistry , ion
Pseudorotaxanes formed by a dibenzo[24]crown‐8 ring ( R ) and a dialkylammonium axle bearing either two E ‐ or two Z ‐azobenzene units ( EE ‐ A or ZZ ‐ A ) revealed useful for the construction of light‐powered molecular machines and motors, as they provide the opportunity of photocontrolling self‐assembly/disassembly processes. The potential energies profiles for the dethreading of these complexes have been investigated by adopting a combination of first‐principles molecular dynamics, metadynamics and quantum‐chemical geometry optimization approaches. While the dethreading of the EE ‐ A axle is associated with a monotonic energy increase, for that of the ZZ ‐ A axle a transition state and an intermediate structure, in which the components are still threaded together, are found. The rate determining step for the dethreading of the ZZ axle has a higher energy barrier than that of the EE axle, in agreement with the experimental kinetic data. Moreover, the results suggest that the elliptic shape of the ring cavity is important for discriminating between the E and Z terminal azobenzene during dethreading.