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pH Tuning of Water‐Soluble Arylazopyrazole Photoswitches

pH Tuning of Water‐Soluble Arylazopyrazole Photoswitches

Authors :
Stefan Weber
Meral Ari
Karsten Parison
Paula Straub
Michael Walter
Simon Ludwanowski
Nils Pompe
Andreas Walther
Somar Kalthoum
Source :
Chemistry (Weinheim an Der Bergstrasse, Germany)
Publication Year :
2020
Publisher :
Wiley, 2020.

Abstract

Arylazopyrazoles are an emerging class of photoswitches with redshifted switching wavelength, high photostationary states, long thermal half‐lives and facile synthetic access. Understanding pathways for a simple modulation of the thermal half‐lives, while keeping other parameters of interest constant, is an important aspect for out‐of‐equilibrium systems design and applications. Here, it is demonstrated that the thermal half‐life of a water‐soluble PEG‐tethered arylazo‐bis(o‐methylated)pyrazole (AAP) can be tuned by more than five orders of magnitude using simple pH adjustment, which is beyond the tunability of azobenzenes. The mechanism of thermal relaxation is investigated by thorough spectroscopic analyses and density functional theory (DFT) calculations. Finally, the concepts of a tunable half‐life are transferred from the molecular scale to the material scale. Based on the photochromic characteristics of E‐ and Z‐AAP, transient information storage is showcased in form of light‐written patterns inside films cast from different pH, which in turn leads to different times of storage. With respect to prospective precisely tunable materials and time‐programmed out‐of‐equilibrium systems, an externally tunable half‐life is likely advantageous over changing the entire system by the replacement of the photoswitch.<br />Arylazopyrazoles are an emerging class of photoswitches with redshifted switching wavelength, high photostationary states, long thermal half‐lives and facile synthetic access. Understanding pathways for a simple modulation of the thermal half‐lives, while keeping other parameters of interest constant, is an important aspect for out‐of‐equilibrium systems design and applications. Here, it is demonstrated that the thermal half‐life of a water‐soluble PEG‐tethered arylazo‐bis(o‐methylated)pyrazole (AAP) can be tuned by more than five orders of magnitude using simple pH adjustment, which is beyond the tunability of azobenzenes.

Details

ISSN :
15213765 and 09476539
Volume :
26
Database :
OpenAIRE
Journal :
Chemistry – A European Journal
Accession number :
edsair.doi.dedup.....f81869660544d4f239fed07f1b149759
Full Text :
https://doi.org/10.1002/chem.202000659