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ortho-Fluoroazobenzenes: visible light switches with very long-lived Z isomers

  • Improving the photochemical properties of molecular photoswitches is crucial for the development of light-responsive systems in materials and life sciences. ortho-Fluoroazobenzenes are a new class of rationally designed photochromic azo compounds with optimized properties, such as the ability to isomerize with visible light only, high photoconversions, and unprecedented robust bistable character. Introducing sigma-electron-withdrawing F atoms ortho to the N=N unit leads to both an effective separation of the n -> pi* bands of the E and Z isomers, thus offering the possibility of using these two transitions for selectively inducing E/Z iso-merizations, and greatly enhanced thermal stability of the Z isomers. Additional para-electron-withdrawing groups (EWGs) work in concert with ortho-F atoms, giving rise to enhanced separation of the n -> pi* transitions. A comprehensive study of the effect of substitution on the key photochemical properties of ortho-fluoroazobenzenes is reported herein. In particular, the position, number, and natureImproving the photochemical properties of molecular photoswitches is crucial for the development of light-responsive systems in materials and life sciences. ortho-Fluoroazobenzenes are a new class of rationally designed photochromic azo compounds with optimized properties, such as the ability to isomerize with visible light only, high photoconversions, and unprecedented robust bistable character. Introducing sigma-electron-withdrawing F atoms ortho to the N=N unit leads to both an effective separation of the n -> pi* bands of the E and Z isomers, thus offering the possibility of using these two transitions for selectively inducing E/Z iso-merizations, and greatly enhanced thermal stability of the Z isomers. Additional para-electron-withdrawing groups (EWGs) work in concert with ortho-F atoms, giving rise to enhanced separation of the n -> pi* transitions. A comprehensive study of the effect of substitution on the key photochemical properties of ortho-fluoroazobenzenes is reported herein. In particular, the position, number, and nature of the EWGs have been varied, and the visible light photoconversions, quantum yields of isomerization, and thermal stabilities have been measured and rationalized by DFT calculations.show moreshow less

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Metadaten
Author details:Christopher Knie, Manuel Martin UtechtORCiDGND, Fangli Zhao, Hannes Kulla, Sergey Kovalenko, Albert M. Brouwer, Peter SaalfrankORCiDGND, Stefan Hecht, David BlegerORCiD
DOI:https://doi.org/10.1002/chem.201404649
ISSN:0947-6539
ISSN:1521-3765
Pubmed ID:https://pubmed.ncbi.nlm.nih.gov/25352421
Title of parent work (English):Chemistry - a European journal
Publisher:Wiley-VCH
Place of publishing:Weinheim
Publication type:Article
Language:English
Year of first publication:2014
Publication year:2014
Release date:2017/03/26
Tag:azobenzenes; photochromism; photoswitches; substituent effects; visible light
Volume:20
Issue:50
Number of pages:10
First page:16492
Last Page:16501
Funding institution:German Research Foundation (DFG) [BL1269/1-1, SFB658]; European Research Council [ERC-2012-STG 308117]
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Chemie
Peer review:Referiert
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