Light- and Redox-Gated Molecular Brakes Consisting of a Pentiptycene Rotor and an Indole Pad
Journal
Journal of the Chinese Chemical Society
Journal Volume
61
Journal Issue
5
Pages
507-516
Date Issued
2014
Author(s)
Abstract
Two photochemically and electrochemically active alkenes 3Me and 3An containing pentiptycene and indole groups have been synthesized and investigated as light and/or redox-gated molecular brakes. The pentiptycene group functions as the four-bladed rotor, the indole group as the brake pad, and the vinylene group as the switch module. The E configuration corresponds to the brake-off state, in which the rotation of the rotor is free with a rotation rate of 108-109 at ambient temperature according to DFT calculations. The Z configuration corresponds to the brake-on state, in which the rotation rate is decreased to 101-102, depending on the N-substituent of indole, according to line-shape analysis of variable temperature 13C NMR spectra. The overall braking effect reaches a factor of 106-108. While the combined photochemical E → Z and electrochemical Z → E switching has a higher capacity than the two-way photochemical switching in the case of 3Me, the switching capacity are comparable for the two methods in 3An. The results also show that photochemical E-Z isomerization is much more reliable than the electrochemical counterpart, as the stability of the redox intermediates plays a critical role in determining the robustness of the molecular brakes via electrochemical switching. The photochemical and/or electrochemical switching between the E and Z isomers of two alkenes substituted with both pentiptycene and indole groups results in a change of the rotation rate as large as 106-108 fold for the pentiptycene group about the pentiptycene-vinylene C-C bond, corresponding to a new generation of light- and redox-gated molecular brakes. © 2014 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
SDGs
Type
journal article