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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:Christopher Knie, Manuel Utecht, Fangli Zhao, Hannes Kulla, Sergey Kovalenko, Albert M. Brouwer, Peter SaalfrankORCiDGND, Stefan Hecht, David Bleger
DOI:https://doi.org/10.1002/chem.201404649
ISSN:0947-6539 (print)
ISSN:1521-3765 (online)
Pubmed Id:http://www.ncbi.nlm.nih.gov/pubmed?term=25352421
Parent Title (English):Chemistry - a European journal
Publisher:Wiley-VCH
Place of publication:Weinheim
Document Type:Article
Language:English
Year of first Publication:2014
Year of Completion:2014
Release Date:2017/03/26
Tag:azobenzenes; photochromism; photoswitches; substituent effects; visible light
Volume:20
Issue:50
Pagenumber:10
First Page:16492
Last Page:16501
Funder: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