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Light‐ and Redox‐Gated Molecular Brakes Consisting of a Pentiptycene Rotor and an Indole Pad
Author(s) -
Kao ChenYi,
Lee ITsun,
Prabhakar Ch.,
Yang JyeShane
Publication year - 2014
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.201400035
Subject(s) - chemistry , redox , indole test , electrochemistry , photochemistry , substituent , stereochemistry , electrode , organic chemistry
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 10 8 ‐10 9 at ambient temperature according to DFT calculations. The Z configuration corresponds to the brake‐on state, in which the rotation rate is decreased to 10 1 ‐10 2 , depending on the N‐substituent of indole, according to line‐shape analysis of variable temperature 13 C NMR spectra. The overall braking effect reaches a factor of 10 6 ‐10 8 . 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.