Efficient electrocatalytic switching of azoheteroarenes in the condensed phases
File(s)
Accepted version
Author(s)
Greenfield, Jake
Mihael, Gerkman
Gibson, Rosie
Han, Grace
Fuchter, Matthew
Type
Journal Article
Abstract
Azo-based photoswitches have shown promise as molecular solar thermal (MOST) materials, due to their ability to store
energy in their metastable Z isomeric form. The energy is then released, in the form of heat, upon photoisomerisation to the
thermodynamically stable E form. However, obtaining a high energy density and recovering the stored energy with high efficiency requires
the materials to be employed in the condensed phase and display a high degree of Z to E switching, respectively: both of which are
challenging to engineer. Here we show that arylazopyrazole motifs undergo efficient redox-induced Z to E switching in both the solution
and condensed phase, to a higher completeness of switching than achieved photochemically. This redox-initiated pathway lowers the
barrier to Z to E isomerization by 27 kJ/mol, whilst in the condensed phase, the efficiency of electrochemical switching is improved by over
an order of magnitude relative to that in the solution state. The influence of the photoswitch’s phase, electrical conductivity, and viscosity
on the electrochemical switching in the condensed phase is reported, culminating in a set of design rules to facilitate further investigations.
We anticipate the use of an alternative stimulus to light will facilitate the application of MOST materials in situations where photo-triggered
heat release is unachievable or inefficient, e.g. indoor or at night. Furthermore, exploiting the electrocatalytic mechanism, whereby a
catalytic amount of charge triggers Z to E switching via a redox process, bypasses the need for fine-tuning of the photoswitching
chromophore to achieve complete Z to E switching, thus providing an alternative approach to photoswitch molecular design.
energy in their metastable Z isomeric form. The energy is then released, in the form of heat, upon photoisomerisation to the
thermodynamically stable E form. However, obtaining a high energy density and recovering the stored energy with high efficiency requires
the materials to be employed in the condensed phase and display a high degree of Z to E switching, respectively: both of which are
challenging to engineer. Here we show that arylazopyrazole motifs undergo efficient redox-induced Z to E switching in both the solution
and condensed phase, to a higher completeness of switching than achieved photochemically. This redox-initiated pathway lowers the
barrier to Z to E isomerization by 27 kJ/mol, whilst in the condensed phase, the efficiency of electrochemical switching is improved by over
an order of magnitude relative to that in the solution state. The influence of the photoswitch’s phase, electrical conductivity, and viscosity
on the electrochemical switching in the condensed phase is reported, culminating in a set of design rules to facilitate further investigations.
We anticipate the use of an alternative stimulus to light will facilitate the application of MOST materials in situations where photo-triggered
heat release is unachievable or inefficient, e.g. indoor or at night. Furthermore, exploiting the electrocatalytic mechanism, whereby a
catalytic amount of charge triggers Z to E switching via a redox process, bypasses the need for fine-tuning of the photoswitching
chromophore to achieve complete Z to E switching, thus providing an alternative approach to photoswitch molecular design.
Date Issued
2021-09-22
Date Acceptance
2021-09-02
Citation
Journal of the American Chemical Society, 2021, 143 (37), pp.15250-15257
ISSN
0002-7863
Publisher
American Chemical Society
Start Page
15250
End Page
15257
Journal / Book Title
Journal of the American Chemical Society
Volume
143
Issue
37
Copyright Statement
© 2021 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in J. Am. Chem. Soc., after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/jacs.1c06359
Sponsor
Engineering & Physical Science Research Council (EPSRC)
The Leverhulme Trust
Identifier
https://pubs.acs.org/doi/10.1021/jacs.1c06359
Grant Number
EP/R00188X/1
RPG-2018-051
Subjects
Science & Technology
Physical Sciences
Chemistry, Multidisciplinary
Chemistry
THERMAL-ENERGY STORAGE
ISOMERIZATION
PHOTOSWITCHES
FLUOROAZOBENZENES
NORBORNADIENE
PERFORMANCE
MECHANISM
RELEASE
General Chemistry
03 Chemical Sciences
Publication Status
Published
Date Publish Online
2021-09-14